[v7,2/2] can: m_can: Add hrtimer to generate software interrupt

  Add an hrtimer to MCAN class device. Each MCAN will have its own
hrtimer instantiated if there is no hardware interrupt found in
device tree M_CAN node.

The hrtimer will generate a software interrupt every 1 ms. In
hrtimer callback, we check if there is a transaction pending by
reading a register, then process by calling the isr if there is.

Signed-off-by: Judith Mendez <jm@ti.com>
---
Changelog:
v7:
- Clean up m_can_platform.c if/else section after removing poll-interval
- Remove poll-interval from patch description
v6:
- Move hrtimer stop/start function calls to m_can_open and m_can_close to
support power suspend/resume
v5:
- Change dev_dbg to dev_info if hardware interrupt exists and polling
is enabled
v4:
- No changes
v3:
- Create a define for 1 ms polling interval
- Change plarform_get_irq to optional to not print error msg
v2:
- Add functionality to check for 'poll-interval' property in MCAN node 
- Add 'polling' flag in driver to check if device is using polling method
- Check for timer polling and hardware interrupt cases, default to
hardware interrupt method
- Change ns_to_ktime() to ms_to_ktime()
---
 drivers/net/can/m_can/m_can.c          | 33 ++++++++++++++++++++++++--
 drivers/net/can/m_can/m_can.h          |  4 ++++
 drivers/net/can/m_can/m_can_platform.c | 25 ++++++++++++++++---
 3 files changed, 57 insertions(+), 5 deletions(-)
  

On 22.05.2023 21:37:49, Judith Mendez wrote:
> Add an hrtimer to MCAN class device. Each MCAN will have its own
> hrtimer instantiated if there is no hardware interrupt found in
> device tree M_CAN node.

Please add a sentence why you introduce polling mode, i.e. there are
SoCs where the M_CAN interrupt is not available on the CPUs (which are
running Linux).

> The hrtimer will generate a software interrupt every 1 ms. In
> hrtimer callback, we check if there is a transaction pending by
> reading a register, then process by calling the isr if there is.
> 
> Signed-off-by: Judith Mendez <jm@ti.com>
> ---
> Changelog:
> v7:
> - Clean up m_can_platform.c if/else section after removing poll-interval
> - Remove poll-interval from patch description
> v6:
> - Move hrtimer stop/start function calls to m_can_open and m_can_close to
> support power suspend/resume
> v5:
> - Change dev_dbg to dev_info if hardware interrupt exists and polling
> is enabled
> v4:
> - No changes
> v3:
> - Create a define for 1 ms polling interval
> - Change plarform_get_irq to optional to not print error msg
> v2:
> - Add functionality to check for 'poll-interval' property in MCAN node 
> - Add 'polling' flag in driver to check if device is using polling method
> - Check for timer polling and hardware interrupt cases, default to
> hardware interrupt method
> - Change ns_to_ktime() to ms_to_ktime()
> ---
>  drivers/net/can/m_can/m_can.c          | 33 ++++++++++++++++++++++++--
>  drivers/net/can/m_can/m_can.h          |  4 ++++
>  drivers/net/can/m_can/m_can_platform.c | 25 ++++++++++++++++---
>  3 files changed, 57 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
> index a5003435802b..f273d989bdff 100644
> --- a/drivers/net/can/m_can/m_can.c
> +++ b/drivers/net/can/m_can/m_can.c
> @@ -11,6 +11,7 @@
>  #include <linux/bitfield.h>
>  #include <linux/can/dev.h>
>  #include <linux/ethtool.h>
> +#include <linux/hrtimer.h>
>  #include <linux/interrupt.h>
>  #include <linux/io.h>
>  #include <linux/iopoll.h>
> @@ -308,6 +309,9 @@ enum m_can_reg {
>  #define TX_EVENT_MM_MASK	GENMASK(31, 24)
>  #define TX_EVENT_TXTS_MASK	GENMASK(15, 0)
>  
> +/* Hrtimer polling interval */
> +#define HRTIMER_POLL_INTERVAL		1
> +
>  /* The ID and DLC registers are adjacent in M_CAN FIFO memory,
>   * and we can save a (potentially slow) bus round trip by combining
>   * reads and writes to them.
> @@ -895,7 +899,7 @@ static int m_can_handle_bus_errors(struct net_device *dev, u32 irqstatus,
>  			netdev_dbg(dev, "Arbitration phase error detected\n");
>  			work_done += m_can_handle_lec_err(dev, lec);
>  		}
> -		
> +

Unrelated change. I've send a separate patch to fix the problem.

>  		if (is_lec_err(dlec)) {
>  			netdev_dbg(dev, "Data phase error detected\n");
>  			work_done += m_can_handle_lec_err(dev, dlec);
> @@ -1414,6 +1418,12 @@ static int m_can_start(struct net_device *dev)
>  
>  	m_can_enable_all_interrupts(cdev);
>  
> +	if (cdev->polling) {
> +		dev_dbg(cdev->dev, "Start hrtimer\n");
> +		hrtimer_start(&cdev->hrtimer, ms_to_ktime(HRTIMER_POLL_INTERVAL),
> +			      HRTIMER_MODE_REL_PINNED);
> +	}
> +
>  	return 0;
>  }
>  
> @@ -1571,6 +1581,11 @@ static void m_can_stop(struct net_device *dev)
>  	/* disable all interrupts */
>  	m_can_disable_all_interrupts(cdev);
>  
> +	if (cdev->polling) {
> +		dev_dbg(cdev->dev, "Disabling the hrtimer\n");
> +		hrtimer_cancel(&cdev->hrtimer);
> +	}
> +

This might be a racy. Please move the disabling of the hrtimer before
disabling all interrupts. This makes it also symmetric with respect to
m_can_start().

>  	/* Set init mode to disengage from the network */
>  	m_can_config_endisable(cdev, true);
>  
> @@ -1793,6 +1808,18 @@ static netdev_tx_t m_can_start_xmit(struct sk_buff *skb,
>  	return NETDEV_TX_OK;
>  }
>  
> +static enum hrtimer_restart hrtimer_callback(struct hrtimer *timer)
> +{
> +	struct m_can_classdev *cdev = container_of(timer, struct
> +						   m_can_classdev, hrtimer);
> +
> +	m_can_isr(0, cdev->net);
> +
> +	hrtimer_forward_now(timer, ms_to_ktime(HRTIMER_POLL_INTERVAL));
> +
> +	return HRTIMER_RESTART;
> +}
> +
>  static int m_can_open(struct net_device *dev)
>  {
>  	struct m_can_classdev *cdev = netdev_priv(dev);
> @@ -1831,9 +1858,11 @@ static int m_can_open(struct net_device *dev)
>  		err = request_threaded_irq(dev->irq, NULL, m_can_isr,
>  					   IRQF_ONESHOT,
>  					   dev->name, dev);
> -	} else {
> +	} else if (!cdev->polling) {
>  		err = request_irq(dev->irq, m_can_isr, IRQF_SHARED, dev->name,
>  				  dev);
> +	} else {
> +		cdev->hrtimer.function = &hrtimer_callback;

I think you can move this assignment to m_can_class_register(). We only
need to set the function once.

>  	}
>  
>  	if (err < 0) {
> diff --git a/drivers/net/can/m_can/m_can.h b/drivers/net/can/m_can/m_can.h
> index a839dc71dc9b..e9db5cce4e68 100644
> --- a/drivers/net/can/m_can/m_can.h
> +++ b/drivers/net/can/m_can/m_can.h
> @@ -15,6 +15,7 @@
>  #include <linux/device.h>
>  #include <linux/dma-mapping.h>
>  #include <linux/freezer.h>
> +#include <linux/hrtimer.h>
>  #include <linux/interrupt.h>
>  #include <linux/io.h>
>  #include <linux/iopoll.h>
> @@ -93,6 +94,9 @@ struct m_can_classdev {
>  	int is_peripheral;
>  
>  	struct mram_cfg mcfg[MRAM_CFG_NUM];
> +
> +	struct hrtimer hrtimer;
> +	bool polling;
>  };
>  
>  struct m_can_classdev *m_can_class_allocate_dev(struct device *dev, int sizeof_priv);
> diff --git a/drivers/net/can/m_can/m_can_platform.c b/drivers/net/can/m_can/m_can_platform.c
> index 94dc82644113..b639c9e645d3 100644
> --- a/drivers/net/can/m_can/m_can_platform.c
> +++ b/drivers/net/can/m_can/m_can_platform.c
> @@ -5,6 +5,7 @@
>  //
>  // Copyright (C) 2018-19 Texas Instruments Incorporated - http://www.ti.com/
>  
> +#include <linux/hrtimer.h>
>  #include <linux/phy/phy.h>
>  #include <linux/platform_device.h>
>  
> @@ -96,12 +97,30 @@ static int m_can_plat_probe(struct platform_device *pdev)
>  		goto probe_fail;
>  
>  	addr = devm_platform_ioremap_resource_byname(pdev, "m_can");
> -	irq = platform_get_irq_byname(pdev, "int0");

I think irq will be uninitialized after this change. Although the
compiler doesn't complain :(

BTW: I think we don't need the "polling" variable in the priv. We can
make use of "irq". "irq" being 0 means use polling.

> -	if (IS_ERR(addr) || irq < 0) {
> -		ret = -EINVAL;
> +	if (IS_ERR(addr)) {
> +		ret = PTR_ERR(addr);
>  		goto probe_fail;
>  	}
>  
> +	if (device_property_present(mcan_class->dev, "interrupts") ||
> +	    device_property_present(mcan_class->dev, "interrupt-names")) {
> +		irq = platform_get_irq_byname(pdev, "int0");
> +		mcan_class->polling = false;
> +		if (irq == -EPROBE_DEFER) {
> +			ret = -EPROBE_DEFER;
> +			goto probe_fail;
> +		}
> +		if (irq < 0) {
> +			ret = -ENXIO;

Please return the original error code.

> +			goto probe_fail;
> +		}
> +	} else {
> +		mcan_class->polling = true;
> +		dev_dbg(mcan_class->dev, "Polling enabled, initialize hrtimer");
> +		hrtimer_init(&mcan_class->hrtimer, CLOCK_MONOTONIC,
> +			     HRTIMER_MODE_REL_PINNED);
> +	}
> +
>  	/* message ram could be shared */
>  	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "message_ram");
>  	if (!res) {

regards,
Marc
  

On Mon, May 22, 2023 at 09:37:49PM -0500, Judith Mendez wrote:
> Add an hrtimer to MCAN class device. Each MCAN will have its own
> hrtimer instantiated if there is no hardware interrupt found in
> device tree M_CAN node.
> 
> The hrtimer will generate a software interrupt every 1 ms. In
> hrtimer callback, we check if there is a transaction pending by
> reading a register, then process by calling the isr if there is.
> 
> Signed-off-by: Judith Mendez <jm@ti.com>

...

> diff --git a/drivers/net/can/m_can/m_can_platform.c b/drivers/net/can/m_can/m_can_platform.c
> index 94dc82644113..b639c9e645d3 100644
> --- a/drivers/net/can/m_can/m_can_platform.c
> +++ b/drivers/net/can/m_can/m_can_platform.c
> @@ -5,6 +5,7 @@
>  //
>  // Copyright (C) 2018-19 Texas Instruments Incorporated - http://www.ti.com/
>  
> +#include <linux/hrtimer.h>
>  #include <linux/phy/phy.h>
>  #include <linux/platform_device.h>
>  
> @@ -96,12 +97,30 @@ static int m_can_plat_probe(struct platform_device *pdev)
>  		goto probe_fail;
>  
>  	addr = devm_platform_ioremap_resource_byname(pdev, "m_can");
> -	irq = platform_get_irq_byname(pdev, "int0");
> -	if (IS_ERR(addr) || irq < 0) {
> -		ret = -EINVAL;
> +	if (IS_ERR(addr)) {
> +		ret = PTR_ERR(addr);
>  		goto probe_fail;
>  	}
>  
> +	if (device_property_present(mcan_class->dev, "interrupts") ||
> +	    device_property_present(mcan_class->dev, "interrupt-names")) {
> +		irq = platform_get_irq_byname(pdev, "int0");
> +		mcan_class->polling = false;
> +		if (irq == -EPROBE_DEFER) {
> +			ret = -EPROBE_DEFER;
> +			goto probe_fail;
> +		}
> +		if (irq < 0) {
> +			ret = -ENXIO;
> +			goto probe_fail;
> +		}
> +	} else {
> +		mcan_class->polling = true;
> +		dev_dbg(mcan_class->dev, "Polling enabled, initialize hrtimer");
> +		hrtimer_init(&mcan_class->hrtimer, CLOCK_MONOTONIC,
> +			     HRTIMER_MODE_REL_PINNED);
> +	}

Hi Judith,

it seems that with this change irq is only set in the first arm of
the above conditional. But later on it is used unconditionally.
That is, it may be used uninitialised.

Reported by gcc-12 as:

 drivers/net/can/m_can/m_can_platform.c: In function 'm_can_plat_probe':
 drivers/net/can/m_can/m_can_platform.c:150:30: warning: 'irq' may be used uninitialized [-Wmaybe-uninitialized]
   150 |         mcan_class->net->irq = irq;
       |         ~~~~~~~~~~~~~~~~~~~~~^~~~~
 drivers/net/can/m_can/m_can_platform.c:86:13: note: 'irq' was declared here
    86 |         int irq, ret = 0;
       |             ^~~

> +
>  	/* message ram could be shared */
>  	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "message_ram");
>  	if (!res) {
> -- 
> 2.17.1
> 
>
  

Hello Marc,

On 5/23/23 1:35 AM, Marc Kleine-Budde wrote:
> On 22.05.2023 21:37:49, Judith Mendez wrote:
>> Add an hrtimer to MCAN class device. Each MCAN will have its own
>> hrtimer instantiated if there is no hardware interrupt found in
>> device tree M_CAN node.
> 
> Please add a sentence why you introduce polling mode, i.e. there are
> SoCs where the M_CAN interrupt is not available on the CPUs (which are
> running Linux).

Sure, I can do that, thanks.

> 
>> The hrtimer will generate a software interrupt every 1 ms. In
>> hrtimer callback, we check if there is a transaction pending by
>> reading a register, then process by calling the isr if there is.
>>
>> Signed-off-by: Judith Mendez <jm@ti.com>
>> ---
>> Changelog:
>> v7:
>> - Clean up m_can_platform.c if/else section after removing poll-interval
>> - Remove poll-interval from patch description
>> v6:
>> - Move hrtimer stop/start function calls to m_can_open and m_can_close to
>> support power suspend/resume
>> v5:
>> - Change dev_dbg to dev_info if hardware interrupt exists and polling
>> is enabled
>> v4:
>> - No changes
>> v3:
>> - Create a define for 1 ms polling interval
>> - Change plarform_get_irq to optional to not print error msg
>> v2:
>> - Add functionality to check for 'poll-interval' property in MCAN node
>> - Add 'polling' flag in driver to check if device is using polling method
>> - Check for timer polling and hardware interrupt cases, default to
>> hardware interrupt method
>> - Change ns_to_ktime() to ms_to_ktime()
>> ---
>>   drivers/net/can/m_can/m_can.c          | 33 ++++++++++++++++++++++++--
>>   drivers/net/can/m_can/m_can.h          |  4 ++++
>>   drivers/net/can/m_can/m_can_platform.c | 25 ++++++++++++++++---
>>   3 files changed, 57 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
>> index a5003435802b..f273d989bdff 100644
>> --- a/drivers/net/can/m_can/m_can.c
>> +++ b/drivers/net/can/m_can/m_can.c
>> @@ -11,6 +11,7 @@
>>   #include <linux/bitfield.h>
>>   #include <linux/can/dev.h>
>>   #include <linux/ethtool.h>
>> +#include <linux/hrtimer.h>
>>   #include <linux/interrupt.h>
>>   #include <linux/io.h>
>>   #include <linux/iopoll.h>
>> @@ -308,6 +309,9 @@ enum m_can_reg {
>>   #define TX_EVENT_MM_MASK	GENMASK(31, 24)
>>   #define TX_EVENT_TXTS_MASK	GENMASK(15, 0)
>>   
>> +/* Hrtimer polling interval */
>> +#define HRTIMER_POLL_INTERVAL		1
>> +
>>   /* The ID and DLC registers are adjacent in M_CAN FIFO memory,
>>    * and we can save a (potentially slow) bus round trip by combining
>>    * reads and writes to them.
>> @@ -895,7 +899,7 @@ static int m_can_handle_bus_errors(struct net_device *dev, u32 irqstatus,
>>   			netdev_dbg(dev, "Arbitration phase error detected\n");
>>   			work_done += m_can_handle_lec_err(dev, lec);
>>   		}
>> -		
>> +
> 
> Unrelated change. I've send a separate patch to fix the problem.

Sorry about this, this was not intentional.

> 
>>   		if (is_lec_err(dlec)) {
>>   			netdev_dbg(dev, "Data phase error detected\n");
>>   			work_done += m_can_handle_lec_err(dev, dlec);
>> @@ -1414,6 +1418,12 @@ static int m_can_start(struct net_device *dev)
>>   
>>   	m_can_enable_all_interrupts(cdev);
>>   
>> +	if (cdev->polling) {
>> +		dev_dbg(cdev->dev, "Start hrtimer\n");
>> +		hrtimer_start(&cdev->hrtimer, ms_to_ktime(HRTIMER_POLL_INTERVAL),
>> +			      HRTIMER_MODE_REL_PINNED);
>> +	}
>> +
>>   	return 0;
>>   }
>>   
>> @@ -1571,6 +1581,11 @@ static void m_can_stop(struct net_device *dev)
>>   	/* disable all interrupts */
>>   	m_can_disable_all_interrupts(cdev);
>>   
>> +	if (cdev->polling) {
>> +		dev_dbg(cdev->dev, "Disabling the hrtimer\n");
>> +		hrtimer_cancel(&cdev->hrtimer);
>> +	}
>> +
> 
> This might be a racy. Please move the disabling of the hrtimer before
> disabling all interrupts. This makes it also symmetric with respect to
> m_can_start().

This makes sense.

> 
>>   	/* Set init mode to disengage from the network */
>>   	m_can_config_endisable(cdev, true);
>>   
>> @@ -1793,6 +1808,18 @@ static netdev_tx_t m_can_start_xmit(struct sk_buff *skb,
>>   	return NETDEV_TX_OK;
>>   }
>>   
>> +static enum hrtimer_restart hrtimer_callback(struct hrtimer *timer)
>> +{
>> +	struct m_can_classdev *cdev = container_of(timer, struct
>> +						   m_can_classdev, hrtimer);
>> +
>> +	m_can_isr(0, cdev->net);
>> +
>> +	hrtimer_forward_now(timer, ms_to_ktime(HRTIMER_POLL_INTERVAL));
>> +
>> +	return HRTIMER_RESTART;
>> +}
>> +
>>   static int m_can_open(struct net_device *dev)
>>   {
>>   	struct m_can_classdev *cdev = netdev_priv(dev);
>> @@ -1831,9 +1858,11 @@ static int m_can_open(struct net_device *dev)
>>   		err = request_threaded_irq(dev->irq, NULL, m_can_isr,
>>   					   IRQF_ONESHOT,
>>   					   dev->name, dev);
>> -	} else {
>> +	} else if (!cdev->polling) {
>>   		err = request_irq(dev->irq, m_can_isr, IRQF_SHARED, dev->name,
>>   				  dev);
>> +	} else {
>> +		cdev->hrtimer.function = &hrtimer_callback;
> 
> I think you can move this assignment to m_can_class_register(). We only
> need to set the function once.

Great idea!

> 
>>   	}
>>   
>>   	if (err < 0) {
>> diff --git a/drivers/net/can/m_can/m_can.h b/drivers/net/can/m_can/m_can.h
>> index a839dc71dc9b..e9db5cce4e68 100644
>> --- a/drivers/net/can/m_can/m_can.h
>> +++ b/drivers/net/can/m_can/m_can.h
>> @@ -15,6 +15,7 @@
>>   #include <linux/device.h>
>>   #include <linux/dma-mapping.h>
>>   #include <linux/freezer.h>
>> +#include <linux/hrtimer.h>
>>   #include <linux/interrupt.h>
>>   #include <linux/io.h>
>>   #include <linux/iopoll.h>
>> @@ -93,6 +94,9 @@ struct m_can_classdev {
>>   	int is_peripheral;
>>   
>>   	struct mram_cfg mcfg[MRAM_CFG_NUM];
>> +
>> +	struct hrtimer hrtimer;
>> +	bool polling;
>>   };
>>   
>>   struct m_can_classdev *m_can_class_allocate_dev(struct device *dev, int sizeof_priv);
>> diff --git a/drivers/net/can/m_can/m_can_platform.c b/drivers/net/can/m_can/m_can_platform.c
>> index 94dc82644113..b639c9e645d3 100644
>> --- a/drivers/net/can/m_can/m_can_platform.c
>> +++ b/drivers/net/can/m_can/m_can_platform.c
>> @@ -5,6 +5,7 @@
>>   //
>>   // Copyright (C) 2018-19 Texas Instruments Incorporated - http://www.ti.com/
>>   
>> +#include <linux/hrtimer.h>
>>   #include <linux/phy/phy.h>
>>   #include <linux/platform_device.h>
>>   
>> @@ -96,12 +97,30 @@ static int m_can_plat_probe(struct platform_device *pdev)
>>   		goto probe_fail;
>>   
>>   	addr = devm_platform_ioremap_resource_byname(pdev, "m_can");
>> -	irq = platform_get_irq_byname(pdev, "int0");
> 
> I think irq will be uninitialized after this change. Although the
> compiler doesn't complain :(

Agreed, I did notice this when testing. But is it an issue?

> 
> BTW: I think we don't need the "polling" variable in the priv. We can
> make use of "irq". "irq" being 0 means use polling.

True, but is using the polling flag easier for the user to read?

> 
>> -	if (IS_ERR(addr) || irq < 0) {
>> -		ret = -EINVAL;
>> +	if (IS_ERR(addr)) {
>> +		ret = PTR_ERR(addr);
>>   		goto probe_fail;
>>   	}
>>   
>> +	if (device_property_present(mcan_class->dev, "interrupts") ||
>> +	    device_property_present(mcan_class->dev, "interrupt-names")) {
>> +		irq = platform_get_irq_byname(pdev, "int0");
>> +		mcan_class->polling = false;
>> +		if (irq == -EPROBE_DEFER) {
>> +			ret = -EPROBE_DEFER;
>> +			goto probe_fail;
>> +		}
>> +		if (irq < 0) {
>> +			ret = -ENXIO;

EINVAL? Wouldn't ENXIO (No such device or address) be more appropriate than
invalid argument?

> 
> Please return the original error code.
> 
>> +			goto probe_fail;
>> +		}
>> +	} else {
>> +		mcan_class->polling = true;
>> +		dev_dbg(mcan_class->dev, "Polling enabled, initialize hrtimer");
>> +		hrtimer_init(&mcan_class->hrtimer, CLOCK_MONOTONIC,
>> +			     HRTIMER_MODE_REL_PINNED);
>> +	}
>> +
>>   	/* message ram could be shared */
>>   	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "message_ram");
>>   	if (!res) {

~Judith
  

Hello Simon,

On 5/23/23 6:09 AM, Simon Horman wrote:
> On Mon, May 22, 2023 at 09:37:49PM -0500, Judith Mendez wrote:
>> Add an hrtimer to MCAN class device. Each MCAN will have its own
>> hrtimer instantiated if there is no hardware interrupt found in
>> device tree M_CAN node.
>>
>> The hrtimer will generate a software interrupt every 1 ms. In
>> hrtimer callback, we check if there is a transaction pending by
>> reading a register, then process by calling the isr if there is.
>>
>> Signed-off-by: Judith Mendez <jm@ti.com>
> 
> ...
> 
>> diff --git a/drivers/net/can/m_can/m_can_platform.c b/drivers/net/can/m_can/m_can_platform.c
>> index 94dc82644113..b639c9e645d3 100644
>> --- a/drivers/net/can/m_can/m_can_platform.c
>> +++ b/drivers/net/can/m_can/m_can_platform.c
>> @@ -5,6 +5,7 @@
>>   //
>>   // Copyright (C) 2018-19 Texas Instruments Incorporated - http://www.ti.com/
>>   
>> +#include <linux/hrtimer.h>
>>   #include <linux/phy/phy.h>
>>   #include <linux/platform_device.h>
>>   
>> @@ -96,12 +97,30 @@ static int m_can_plat_probe(struct platform_device *pdev)
>>   		goto probe_fail;
>>   
>>   	addr = devm_platform_ioremap_resource_byname(pdev, "m_can");
>> -	irq = platform_get_irq_byname(pdev, "int0");
>> -	if (IS_ERR(addr) || irq < 0) {
>> -		ret = -EINVAL;
>> +	if (IS_ERR(addr)) {
>> +		ret = PTR_ERR(addr);
>>   		goto probe_fail;
>>   	}
>>   
>> +	if (device_property_present(mcan_class->dev, "interrupts") ||
>> +	    device_property_present(mcan_class->dev, "interrupt-names")) {
>> +		irq = platform_get_irq_byname(pdev, "int0");
>> +		mcan_class->polling = false;
>> +		if (irq == -EPROBE_DEFER) {
>> +			ret = -EPROBE_DEFER;
>> +			goto probe_fail;
>> +		}
>> +		if (irq < 0) {
>> +			ret = -ENXIO;
>> +			goto probe_fail;
>> +		}
>> +	} else {
>> +		mcan_class->polling = true;
>> +		dev_dbg(mcan_class->dev, "Polling enabled, initialize hrtimer");
>> +		hrtimer_init(&mcan_class->hrtimer, CLOCK_MONOTONIC,
>> +			     HRTIMER_MODE_REL_PINNED);
>> +	}
> 
> Hi Judith,
> 
> it seems that with this change irq is only set in the first arm of
> the above conditional. But later on it is used unconditionally.
> That is, it may be used uninitialised.
> 
> Reported by gcc-12 as:
> 
>   drivers/net/can/m_can/m_can_platform.c: In function 'm_can_plat_probe':
>   drivers/net/can/m_can/m_can_platform.c:150:30: warning: 'irq' may be used uninitialized [-Wmaybe-uninitialized]
>     150 |         mcan_class->net->irq = irq;
>         |         ~~~~~~~~~~~~~~~~~~~~~^~~~~
>   drivers/net/can/m_can/m_can_platform.c:86:13: note: 'irq' was declared here
>      86 |         int irq, ret = 0;
>         |             ^~~
> 

Maybe a good solution is to initialize irq=0 here.

>> +
>>   	/* message ram could be shared */
>>   	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "message_ram");
>>   	if (!res) {
>> -- 
>> 2.17.1


~Judith
  

On Wed, May 24, 2023 at 04:29:01PM -0500, Judith Mendez wrote:
> Hello Simon,
> 
> On 5/23/23 6:09 AM, Simon Horman wrote:
> > On Mon, May 22, 2023 at 09:37:49PM -0500, Judith Mendez wrote:
> > > Add an hrtimer to MCAN class device. Each MCAN will have its own
> > > hrtimer instantiated if there is no hardware interrupt found in
> > > device tree M_CAN node.
> > > 
> > > The hrtimer will generate a software interrupt every 1 ms. In
> > > hrtimer callback, we check if there is a transaction pending by
> > > reading a register, then process by calling the isr if there is.
> > > 
> > > Signed-off-by: Judith Mendez <jm@ti.com>
> > 
> > ...
> > 
> > > diff --git a/drivers/net/can/m_can/m_can_platform.c b/drivers/net/can/m_can/m_can_platform.c
> > > index 94dc82644113..b639c9e645d3 100644
> > > --- a/drivers/net/can/m_can/m_can_platform.c
> > > +++ b/drivers/net/can/m_can/m_can_platform.c
> > > @@ -5,6 +5,7 @@
> > >   //
> > >   // Copyright (C) 2018-19 Texas Instruments Incorporated - http://www.ti.com/
> > > +#include <linux/hrtimer.h>
> > >   #include <linux/phy/phy.h>
> > >   #include <linux/platform_device.h>
> > > @@ -96,12 +97,30 @@ static int m_can_plat_probe(struct platform_device *pdev)
> > >   		goto probe_fail;
> > >   	addr = devm_platform_ioremap_resource_byname(pdev, "m_can");
> > > -	irq = platform_get_irq_byname(pdev, "int0");
> > > -	if (IS_ERR(addr) || irq < 0) {
> > > -		ret = -EINVAL;
> > > +	if (IS_ERR(addr)) {
> > > +		ret = PTR_ERR(addr);
> > >   		goto probe_fail;
> > >   	}
> > > +	if (device_property_present(mcan_class->dev, "interrupts") ||
> > > +	    device_property_present(mcan_class->dev, "interrupt-names")) {
> > > +		irq = platform_get_irq_byname(pdev, "int0");
> > > +		mcan_class->polling = false;
> > > +		if (irq == -EPROBE_DEFER) {
> > > +			ret = -EPROBE_DEFER;
> > > +			goto probe_fail;
> > > +		}
> > > +		if (irq < 0) {
> > > +			ret = -ENXIO;
> > > +			goto probe_fail;
> > > +		}
> > > +	} else {
> > > +		mcan_class->polling = true;
> > > +		dev_dbg(mcan_class->dev, "Polling enabled, initialize hrtimer");
> > > +		hrtimer_init(&mcan_class->hrtimer, CLOCK_MONOTONIC,
> > > +			     HRTIMER_MODE_REL_PINNED);
> > > +	}
> > 
> > Hi Judith,
> > 
> > it seems that with this change irq is only set in the first arm of
> > the above conditional. But later on it is used unconditionally.
> > That is, it may be used uninitialised.
> > 
> > Reported by gcc-12 as:
> > 
> >   drivers/net/can/m_can/m_can_platform.c: In function 'm_can_plat_probe':
> >   drivers/net/can/m_can/m_can_platform.c:150:30: warning: 'irq' may be used uninitialized [-Wmaybe-uninitialized]
> >     150 |         mcan_class->net->irq = irq;
> >         |         ~~~~~~~~~~~~~~~~~~~~~^~~~~
> >   drivers/net/can/m_can/m_can_platform.c:86:13: note: 'irq' was declared here
> >      86 |         int irq, ret = 0;
> >         |             ^~~
> > 
> 
> Maybe a good solution is to initialize irq=0 here.

If it is valid for mcan_class->net->irq to be 0 in this case,
then, yes, I agree.

> > > +
> > >   	/* message ram could be shared */
> > >   	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "message_ram");
> > >   	if (!res) {
> > > -- 
> > > 2.17.1
> 
> 
> ~Judith