diff mbox series

[v3,2/3] fpga: microchip-spi: rewrite status polling in a time measurable way

Message ID 20221227100450.2257-3-i.bornyakov@metrotek.ru
State New
Headers
Series Reliability improvements for Microchip MPF FPGA manager |

Commit Message

Ivan Bornyakov Dec. 27, 2022, 10:04 a.m. UTC 
  Original busy loop with retries count in mpf_poll_status() is not too
reliable, as it takes different times on different systems. Replace it
with read_poll_timeout() macro.

While at it, fix polling stop condition to met function's original
intention declared in the comment. The issue with original polling stop
condition is that it stops if any of mask bits is set, while intention
was to stop if all mask bits is set. This was not noticible because only
MPF_STATUS_READY is passed as mask argument and it is BIT(1).

Fixes: 5f8d4a900830 ("fpga: microchip-spi: add Microchip MPF FPGA manager")
Signed-off-by: Ivan Bornyakov <i.bornyakov@metrotek.ru>
---
 drivers/fpga/microchip-spi.c | 24 ++++++++++--------------
 1 file changed, 10 insertions(+), 14 deletions(-)

Comments

Ilpo Järvinen Dec. 27, 2022, 10:22 a.m. UTC | #1 
On Tue, 27 Dec 2022, Ivan Bornyakov wrote:

> Original busy loop with retries count in mpf_poll_status() is not too
> reliable, as it takes different times on different systems. Replace it
> with read_poll_timeout() macro.
> 
> While at it, fix polling stop condition to met function's original
> intention declared in the comment. The issue with original polling stop
> condition is that it stops if any of mask bits is set, while intention
> was to stop if all mask bits is set. This was not noticible because only
> MPF_STATUS_READY is passed as mask argument and it is BIT(1).
> 
> Fixes: 5f8d4a900830 ("fpga: microchip-spi: add Microchip MPF FPGA manager")
> Signed-off-by: Ivan Bornyakov <i.bornyakov@metrotek.ru>
> ---
>  drivers/fpga/microchip-spi.c | 24 ++++++++++--------------
>  1 file changed, 10 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/fpga/microchip-spi.c b/drivers/fpga/microchip-spi.c
> index e72fedd93a27..8d1d9476d0cc 100644
> --- a/drivers/fpga/microchip-spi.c
> +++ b/drivers/fpga/microchip-spi.c
> @@ -6,6 +6,7 @@
>  #include <asm/unaligned.h>
>  #include <linux/delay.h>
>  #include <linux/fpga/fpga-mgr.h>
> +#include <linux/iopoll.h>
>  #include <linux/module.h>
>  #include <linux/of_device.h>
>  #include <linux/spi/spi.h>
> @@ -33,7 +34,7 @@
>  
>  #define	MPF_BITS_PER_COMPONENT_SIZE	22
>  
> -#define	MPF_STATUS_POLL_RETRIES		10000
> +#define	MPF_STATUS_POLL_TIMEOUT		(2 * USEC_PER_SEC)
>  #define	MPF_STATUS_BUSY			BIT(0)
>  #define	MPF_STATUS_READY		BIT(1)
>  #define	MPF_STATUS_SPI_VIOLATION	BIT(2)
> @@ -197,21 +198,16 @@ static int mpf_ops_parse_header(struct fpga_manager *mgr,
>  /* Poll HW status until busy bit is cleared and mask bits are set. */
>  static int mpf_poll_status(struct mpf_priv *priv, u8 mask)
>  {
> -	int status, retries = MPF_STATUS_POLL_RETRIES;
> +	int ret, status;
>  
> -	while (retries--) {
> -		status = mpf_read_status(priv);
> -		if (status < 0)
> -			return status;
> -
> -		if (status & MPF_STATUS_BUSY)
> -			continue;
> -
> -		if (!mask || (status & mask))
> -			return status;
> -	}
> +	ret = read_poll_timeout(mpf_read_status, status,
> +				(status < 0) ||
> +				((status & (MPF_STATUS_BUSY | mask)) == mask),
> +				0, MPF_STATUS_POLL_TIMEOUT, false, priv);
> +	if (ret < 0)
> +		return ret;
>  
> -	return -EBUSY;
> +	return status;
>  }
>  
>  static int mpf_spi_write(struct mpf_priv *priv, const void *buf, size_t buf_size)

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Conor Dooley Dec. 28, 2022, 2:50 p.m. UTC | #2 
On Tue, Dec 27, 2022 at 01:04:49PM +0300, Ivan Bornyakov wrote:
> Original busy loop with retries count in mpf_poll_status() is not too
> reliable, as it takes different times on different systems. Replace it
> with read_poll_timeout() macro.
> 
> While at it, fix polling stop condition to met function's original
> intention declared in the comment. The issue with original polling stop
> condition is that it stops if any of mask bits is set, while intention
> was to stop if all mask bits is set. This was not noticible because only
> MPF_STATUS_READY is passed as mask argument and it is BIT(1).
> 
> Fixes: 5f8d4a900830 ("fpga: microchip-spi: add Microchip MPF FPGA manager")
> Signed-off-by: Ivan Bornyakov <i.bornyakov@metrotek.ru>
> ---
>  drivers/fpga/microchip-spi.c | 24 ++++++++++--------------
>  1 file changed, 10 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/fpga/microchip-spi.c b/drivers/fpga/microchip-spi.c
> index e72fedd93a27..8d1d9476d0cc 100644
> --- a/drivers/fpga/microchip-spi.c
> +++ b/drivers/fpga/microchip-spi.c
> @@ -6,6 +6,7 @@
>  #include <asm/unaligned.h>
>  #include <linux/delay.h>
>  #include <linux/fpga/fpga-mgr.h>
> +#include <linux/iopoll.h>
>  #include <linux/module.h>
>  #include <linux/of_device.h>
>  #include <linux/spi/spi.h>
> @@ -33,7 +34,7 @@
>  
>  #define	MPF_BITS_PER_COMPONENT_SIZE	22
>  
> -#define	MPF_STATUS_POLL_RETRIES		10000
> +#define	MPF_STATUS_POLL_TIMEOUT		(2 * USEC_PER_SEC)
>  #define	MPF_STATUS_BUSY			BIT(0)
>  #define	MPF_STATUS_READY		BIT(1)
>  #define	MPF_STATUS_SPI_VIOLATION	BIT(2)
> @@ -197,21 +198,16 @@ static int mpf_ops_parse_header(struct fpga_manager *mgr,
>  /* Poll HW status until busy bit is cleared and mask bits are set. */
>  static int mpf_poll_status(struct mpf_priv *priv, u8 mask)
>  {
> -	int status, retries = MPF_STATUS_POLL_RETRIES;
> +	int ret, status;
>  
> -	while (retries--) {
> -		status = mpf_read_status(priv);
> -		if (status < 0)
> -			return status;
> -
> -		if (status & MPF_STATUS_BUSY)
> -			continue;
> -
> -		if (!mask || (status & mask))
> -			return status;
> -	}

Would you mind moving the small comment before the function down to here
and mentioning handling the failure case?
The current implementation is a bit easier to understand than the new
version that's wrapped in read_poll_timeout().

Otherwise, change seems like a good idea.
Acked-by: Conor Dooley <conor.dooley@microchip.com>

> +	ret = read_poll_timeout(mpf_read_status, status,
> +				(status < 0) ||
> +				((status & (MPF_STATUS_BUSY | mask)) == mask),
> +	if (ret < 0)
> +		return ret;
>  
> -	return -EBUSY;
> +	return status;
>  }
>  
>  static int mpf_spi_write(struct mpf_priv *priv, const void *buf, size_t buf_size)
> -- 
> 2.38.2
> 
>
diff mbox series

Patch

diff --git a/drivers/fpga/microchip-spi.c b/drivers/fpga/microchip-spi.c
index e72fedd93a27..8d1d9476d0cc 100644
--- a/drivers/fpga/microchip-spi.c
+++ b/drivers/fpga/microchip-spi.c
@@ -6,6 +6,7 @@ 
 #include <asm/unaligned.h>
 #include <linux/delay.h>
 #include <linux/fpga/fpga-mgr.h>
+#include <linux/iopoll.h>
 #include <linux/module.h>
 #include <linux/of_device.h>
 #include <linux/spi/spi.h>
@@ -33,7 +34,7 @@ 
 
 #define	MPF_BITS_PER_COMPONENT_SIZE	22
 
-#define	MPF_STATUS_POLL_RETRIES		10000
+#define	MPF_STATUS_POLL_TIMEOUT		(2 * USEC_PER_SEC)
 #define	MPF_STATUS_BUSY			BIT(0)
 #define	MPF_STATUS_READY		BIT(1)
 #define	MPF_STATUS_SPI_VIOLATION	BIT(2)
@@ -197,21 +198,16 @@  static int mpf_ops_parse_header(struct fpga_manager *mgr,
 /* Poll HW status until busy bit is cleared and mask bits are set. */
 static int mpf_poll_status(struct mpf_priv *priv, u8 mask)
 {
-	int status, retries = MPF_STATUS_POLL_RETRIES;
+	int ret, status;
 
-	while (retries--) {
-		status = mpf_read_status(priv);
-		if (status < 0)
-			return status;
-
-		if (status & MPF_STATUS_BUSY)
-			continue;
-
-		if (!mask || (status & mask))
-			return status;
-	}
+	ret = read_poll_timeout(mpf_read_status, status,
+				(status < 0) ||
+				((status & (MPF_STATUS_BUSY | mask)) == mask),
+				0, MPF_STATUS_POLL_TIMEOUT, false, priv);
+	if (ret < 0)
+		return ret;
 
-	return -EBUSY;
+	return status;
 }
 
 static int mpf_spi_write(struct mpf_priv *priv, const void *buf, size_t buf_size)