rtc: mpfs: fix counter upload completion condition

[PATCH v1] rtc: mpfs: fix counter upload completion condition

Posted by Conor Dooley 4 weeks, 1 day ago

From: Conor Dooley <conor.dooley@microchip.com>

The condition that needs to be checked for upload completion is the
UPLOAD bit in the completion register going low. The original iterations
of this driver used a do-while and this was converted to a
read_poll_timeout() during upstreaming without the condition being
inverted as it should have been.

I suspect that this went unnoticed until now because a) the first read
was done when the bit was still set, immediately completing the
read_poll_timeout() and b) because the RTC doesn't hold time when power
is removed from the SoC reducing its utility (I for one keep it
disabled). If my first suspicion was true when the driver was
upstreamed, it's not true any longer though, hence the detection of the
problem.

Fixes: 0b31d703598dc ("rtc: Add driver for Microchip PolarFire SoC")
CC: stable@vger.kernel.org
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
---
CC: Valentina.FernandezAlanis@microchip.com
CC: Conor Dooley <conor.dooley@microchip.com>
CC: Daire McNamara <daire.mcnamara@microchip.com>
CC: Alexandre Belloni <alexandre.belloni@bootlin.com>
CC: linux-riscv@lists.infradead.org
CC: linux-rtc@vger.kernel.org
CC: linux-kernel@vger.kernel.org
---
 drivers/rtc/rtc-mpfs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/rtc/rtc-mpfs.c b/drivers/rtc/rtc-mpfs.c
index 6aa3eae575d2a..ece6de4a6adbd 100644
--- a/drivers/rtc/rtc-mpfs.c
+++ b/drivers/rtc/rtc-mpfs.c
@@ -112,7 +112,7 @@ static int mpfs_rtc_settime(struct device *dev, struct rtc_time *tm)
 	ctrl |= CONTROL_UPLOAD_BIT;
 	writel(ctrl, rtcdev->base + CONTROL_REG);
 
-	ret = read_poll_timeout(readl, prog, prog & CONTROL_UPLOAD_BIT, 0, UPLOAD_TIMEOUT_US,
+	ret = read_poll_timeout(readl, prog, !(prog & CONTROL_UPLOAD_BIT), 0, UPLOAD_TIMEOUT_US,
 				false, rtcdev->base + CONTROL_REG);
 	if (ret) {
 		dev_err(dev, "timed out uploading time to rtc");
-- 
2.53.0

Re: [PATCH v1] rtc: mpfs: fix counter upload completion condition

Posted by Valentina.FernandezAlanis@microchip.com 1 week, 3 days ago

On 13/05/2026 18:55, Conor Dooley wrote:
> From: Conor Dooley <conor.dooley@microchip.com>
>
> The condition that needs to be checked for upload completion is the
> UPLOAD bit in the completion register going low. The original iterations
> of this driver used a do-while and this was converted to a
> read_poll_timeout() during upstreaming without the condition being
> inverted as it should have been.
>
> I suspect that this went unnoticed until now because a) the first read
> was done when the bit was still set, immediately completing the
> read_poll_timeout() and b) because the RTC doesn't hold time when power
> is removed from the SoC reducing its utility (I for one keep it
> disabled). If my first suspicion was true when the driver was
> upstreamed, it's not true any longer though, hence the detection of the
> problem.
>
> Fixes: 0b31d703598dc ("rtc: Add driver for Microchip PolarFire SoC")
> CC: stable@vger.kernel.org
> Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Tested-by: Valentina Fernandez <valentina.fernandezalanis@microchip.com>
> ---
> CC: Valentina.FernandezAlanis@microchip.com
> CC: Conor Dooley <conor.dooley@microchip.com>
> CC: Daire McNamara <daire.mcnamara@microchip.com>
> CC: Alexandre Belloni <alexandre.belloni@bootlin.com>
> CC: linux-riscv@lists.infradead.org
> CC: linux-rtc@vger.kernel.org
> CC: linux-kernel@vger.kernel.org
> ---
>   drivers/rtc/rtc-mpfs.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/rtc/rtc-mpfs.c b/drivers/rtc/rtc-mpfs.c
> index 6aa3eae575d2a..ece6de4a6adbd 100644
> --- a/drivers/rtc/rtc-mpfs.c
> +++ b/drivers/rtc/rtc-mpfs.c
> @@ -112,7 +112,7 @@ static int mpfs_rtc_settime(struct device *dev, struct rtc_time *tm)
>   	ctrl |= CONTROL_UPLOAD_BIT;
>   	writel(ctrl, rtcdev->base + CONTROL_REG);
>   
> -	ret = read_poll_timeout(readl, prog, prog & CONTROL_UPLOAD_BIT, 0, UPLOAD_TIMEOUT_US,
> +	ret = read_poll_timeout(readl, prog, !(prog & CONTROL_UPLOAD_BIT), 0, UPLOAD_TIMEOUT_US,
>   				false, rtcdev->base + CONTROL_REG);
>   	if (ret) {
>   		dev_err(dev, "timed out uploading time to rtc");

Re: [PATCH v1] rtc: mpfs: fix counter upload completion condition

Posted by Conor Dooley 1 week, 3 days ago

Hey Alexandrew,

On Wed, May 13, 2026 at 06:55:55PM +0100, Conor Dooley wrote:
> From: Conor Dooley <conor.dooley@microchip.com>
> 
> The condition that needs to be checked for upload completion is the
> UPLOAD bit in the completion register going low. The original iterations
> of this driver used a do-while and this was converted to a
> read_poll_timeout() during upstreaming without the condition being
> inverted as it should have been.
> 
> I suspect that this went unnoticed until now because a) the first read
> was done when the bit was still set, immediately completing the
> read_poll_timeout() and b) because the RTC doesn't hold time when power
> is removed from the SoC reducing its utility (I for one keep it
> disabled). If my first suspicion was true when the driver was
> upstreamed, it's not true any longer though, hence the detection of the
> problem.
> 
> Fixes: 0b31d703598dc ("rtc: Add driver for Microchip PolarFire SoC")
> CC: stable@vger.kernel.org
> Signed-off-by: Conor Dooley <conor.dooley@microchip.com>

Any chance this could be applied as 7.1 fixes material?

Apologies if I missed an application mail somewhere,
Conor.

> ---
> CC: Valentina.FernandezAlanis@microchip.com
> CC: Conor Dooley <conor.dooley@microchip.com>
> CC: Daire McNamara <daire.mcnamara@microchip.com>
> CC: Alexandre Belloni <alexandre.belloni@bootlin.com>
> CC: linux-riscv@lists.infradead.org
> CC: linux-rtc@vger.kernel.org
> CC: linux-kernel@vger.kernel.org
> ---
>  drivers/rtc/rtc-mpfs.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/rtc/rtc-mpfs.c b/drivers/rtc/rtc-mpfs.c
> index 6aa3eae575d2a..ece6de4a6adbd 100644
> --- a/drivers/rtc/rtc-mpfs.c
> +++ b/drivers/rtc/rtc-mpfs.c
> @@ -112,7 +112,7 @@ static int mpfs_rtc_settime(struct device *dev, struct rtc_time *tm)
>  	ctrl |= CONTROL_UPLOAD_BIT;
>  	writel(ctrl, rtcdev->base + CONTROL_REG);
>  
> -	ret = read_poll_timeout(readl, prog, prog & CONTROL_UPLOAD_BIT, 0, UPLOAD_TIMEOUT_US,
> +	ret = read_poll_timeout(readl, prog, !(prog & CONTROL_UPLOAD_BIT), 0, UPLOAD_TIMEOUT_US,
>  				false, rtcdev->base + CONTROL_REG);
>  	if (ret) {
>  		dev_err(dev, "timed out uploading time to rtc");
> -- 
> 2.53.0
>