diff mbox series

[v7,2/2] irqchip: irq-qcom-mpm: Support passing a slice of SRAM as reg space

Message ID 20230328-topic-msgram_mpm-v7-2-6ee2bfeaac2c@linaro.org
State New
Headers
Series Resolve MPM register space situation |

Commit Message

Konrad Dybcio Nov. 27, 2023, 3:52 p.m. UTC 
  The MPM hardware is accessible to us from the ARM CPUs through a shared
memory region (RPM MSG RAM) that's also concurrently accessed by other
kinds of cores on the system (like modem, ADSP etc.). Modeling this
relation in a (somewhat) sane manner in the device tree basically
requires us to either present the MPM as a child of said memory region
(which makes little sense, as a mapped memory carveout is not a bus),
define nodes which bleed their register spaces into one another, or
passing their slice of the MSG RAM through some kind of a property.

Go with the third option and add a way to map a region passed through
the "qcom,rpm-msg-ram" property as our register space.

The current way of using 'reg' is preserved for ABI reasons.

Acked-by: Shawn Guo <shawn.guo@linaro.org>
Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
---
 drivers/irqchip/irq-qcom-mpm.c | 26 +++++++++++++++++++++++---
 1 file changed, 23 insertions(+), 3 deletions(-)

Comments

Thomas Gleixner Dec. 8, 2023, 2:37 p.m. UTC | #1 
On Mon, Nov 27 2023 at 16:52, Konrad Dybcio wrote:

The prefix in the subject is wrong. Also please write out register. This
is not Xitter.

> The MPM hardware is accessible to us from the ARM CPUs through a shared

to us? Can you access that hardware? I doubt it.

Please use neutral tone as documented in Documentation/process/

> memory region (RPM MSG RAM) that's also concurrently accessed by other
> kinds of cores on the system (like modem, ADSP etc.). Modeling this
> relation in a (somewhat) sane manner in the device tree basically
> requires us to either present the MPM as a child of said memory region
> (which makes little sense, as a mapped memory carveout is not a bus),
> define nodes which bleed their register spaces into one another, or
> passing their slice of the MSG RAM through some kind of a property.
>
> Go with the third option and add a way to map a region passed through
> the "qcom,rpm-msg-ram" property as our register space.
>
> The current way of using 'reg' is preserved for ABI reasons.

It's not an ABI reason. It's backwards compatibility with old device
trees, right?

I'll fix it up for you this time. No need to resend.

Thanks,

        tglx
Konrad Dybcio Dec. 9, 2023, 2:23 p.m. UTC | #2 
On 8.12.2023 15:37, Thomas Gleixner wrote:
> On Mon, Nov 27 2023 at 16:52, Konrad Dybcio wrote:
> 
> The prefix in the subject is wrong. Also please write out register. This
> is not Xitter.
Had a feeling it would be too long, but actually it'd be perfect
72 chars :)

> 
>> The MPM hardware is accessible to us from the ARM CPUs through a shared
> 
> to us? Can you access that hardware? I doubt it.
With a small enough "stick".. but I get your point

> 
> Please use neutral tone as documented in Documentation/process/
> 
>> memory region (RPM MSG RAM) that's also concurrently accessed by other
>> kinds of cores on the system (like modem, ADSP etc.). Modeling this
>> relation in a (somewhat) sane manner in the device tree basically
>> requires us to either present the MPM as a child of said memory region
>> (which makes little sense, as a mapped memory carveout is not a bus),
>> define nodes which bleed their register spaces into one another, or
>> passing their slice of the MSG RAM through some kind of a property.
>>
>> Go with the third option and add a way to map a region passed through
>> the "qcom,rpm-msg-ram" property as our register space.
>>
>> The current way of using 'reg' is preserved for ABI reasons.
> 
> It's not an ABI reason. It's backwards compatibility with old device
> trees, right?
Yes, I thought of something else.

> 
> I'll fix it up for you this time. No need to resend.
Thanks!

Konrad
diff mbox series

Patch

diff --git a/drivers/irqchip/irq-qcom-mpm.c b/drivers/irqchip/irq-qcom-mpm.c
index 7124565234a5..cda5838d2232 100644
--- a/drivers/irqchip/irq-qcom-mpm.c
+++ b/drivers/irqchip/irq-qcom-mpm.c
@@ -14,6 +14,7 @@ 
 #include <linux/mailbox_client.h>
 #include <linux/module.h>
 #include <linux/of.h>
+#include <linux/of_address.h>
 #include <linux/of_platform.h>
 #include <linux/platform_device.h>
 #include <linux/pm_domain.h>
@@ -322,8 +323,10 @@  static int qcom_mpm_init(struct device_node *np, struct device_node *parent)
 	struct device *dev = &pdev->dev;
 	struct irq_domain *parent_domain;
 	struct generic_pm_domain *genpd;
+	struct device_node *msgram_np;
 	struct qcom_mpm_priv *priv;
 	unsigned int pin_cnt;
+	struct resource res;
 	int i, irq;
 	int ret;
 
@@ -374,9 +377,26 @@  static int qcom_mpm_init(struct device_node *np, struct device_node *parent)
 
 	raw_spin_lock_init(&priv->lock);
 
-	priv->base = devm_platform_ioremap_resource(pdev, 0);
-	if (IS_ERR(priv->base))
-		return PTR_ERR(priv->base);
+	/* If we have a handle to an RPM message ram partition, use it. */
+	msgram_np = of_parse_phandle(np, "qcom,rpm-msg-ram", 0);
+	if (msgram_np) {
+		ret = of_address_to_resource(msgram_np, 0, &res);
+		if (ret) {
+			of_node_put(msgram_np);
+			return ret;
+		}
+
+		/* Don't use devm_ioremap_resource, as we're accessing a shared region. */
+		priv->base = devm_ioremap(dev, res.start, resource_size(&res));
+		of_node_put(msgram_np);
+		if (IS_ERR(priv->base))
+			return PTR_ERR(priv->base);
+	} else {
+		/* Otherwise, fall back to simple MMIO. */
+		priv->base = devm_platform_ioremap_resource(pdev, 0);
+		if (IS_ERR(priv->base))
+			return PTR_ERR(priv->base);
+	}
 
 	for (i = 0; i < priv->reg_stride; i++) {
 		qcom_mpm_write(priv, MPM_REG_ENABLE, i, 0);