[PATCH v2] usb: cdnsp: Fix issue with detecting command completion event

[PATCH v2] usb: cdnsp: Fix issue with detecting command completion event

[Pawel Laszczak]

In some cases, there is a small-time gap in which CMD_RING_BUSY
can be cleared by controller but adding command completion event
to event ring will be delayed. As the result driver will return
error code.
This behavior has been detected on usbtest driver (test 9) with
configuration including ep1in/ep1out bulk and ep2in/ep2out isoc
endpoint.
Probably this gap occurred because controller was busy with adding
some other events to event ring.
The CMD_RING_BUSY is cleared to '0' when the Command Descriptor
has been executed and not when command completion event has been
added to event ring.

To fix this issue for this test the small delay is sufficient
less than 10us) but to make sure the problem doesn't happen again
in the future the patch introduces 10 retries to check with delay
about 20us before returning error code.

Fixes: 3d82904559f4 ("usb: cdnsp: cdns3 Add main part of Cadence USBSSP DRD Driver")
cc: stable@vger.kernel.org
Signed-off-by: Pawel Laszczak <pawell@cadence.com>
---
Changelog:
v2:
- replaced usleep_range with udelay
- increased retry counter and decreased the udelay value

 drivers/usb/cdns3/cdnsp-gadget.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/cdns3/cdnsp-gadget.c b/drivers/usb/cdns3/cdnsp-gadget.c
index 4824a10df07e..58650b7f4173 100644
--- a/drivers/usb/cdns3/cdnsp-gadget.c
+++ b/drivers/usb/cdns3/cdnsp-gadget.c
@@ -547,6 +547,7 @@ int cdnsp_wait_for_cmd_compl(struct cdnsp_device *pdev)
 	dma_addr_t cmd_deq_dma;
 	union cdnsp_trb *event;
 	u32 cycle_state;
+	u32 retry = 10;
 	int ret, val;
 	u64 cmd_dma;
 	u32  flags;
@@ -578,8 +579,23 @@ int cdnsp_wait_for_cmd_compl(struct cdnsp_device *pdev)
 		flags = le32_to_cpu(event->event_cmd.flags);
 
 		/* Check the owner of the TRB. */
-		if ((flags & TRB_CYCLE) != cycle_state)
+		if ((flags & TRB_CYCLE) != cycle_state) {
+			/*
+			 * Give some extra time to get chance controller
+			 * to finish command before returning error code.
+			 * Checking CMD_RING_BUSY is not sufficient because
+			 * this bit is cleared to '0' when the Command
+			 * Descriptor has been executed by controller
+			 * and not when command completion event has
+			 * be added to event ring.
+			 */
+			if (retry--) {
+				udelay(20);
+				continue;
+			}
+
 			return -EINVAL;
+		}
 
 		cmd_dma = le64_to_cpu(event->event_cmd.cmd_trb);
 
-- 
2.43.0

Re: [PATCH v2] usb: cdnsp: Fix issue with detecting command completion event

[Peter Chen (CIX)]

On 25-05-13 05:30:09, Pawel Laszczak wrote:
> In some cases, there is a small-time gap in which CMD_RING_BUSY
> can be cleared by controller but adding command completion event
> to event ring will be delayed. As the result driver will return
> error code.
> This behavior has been detected on usbtest driver (test 9) with
> configuration including ep1in/ep1out bulk and ep2in/ep2out isoc
> endpoint.
> Probably this gap occurred because controller was busy with adding
> some other events to event ring.
> The CMD_RING_BUSY is cleared to '0' when the Command Descriptor
> has been executed and not when command completion event has been
> added to event ring.
> 
> To fix this issue for this test the small delay is sufficient
> less than 10us) but to make sure the problem doesn't happen again
> in the future the patch introduces 10 retries to check with delay
> about 20us before returning error code.

Does the ./scripts/checkpatch.pl report warning if the delay time is
20us for udelay?

Peter
> 
> Fixes: 3d82904559f4 ("usb: cdnsp: cdns3 Add main part of Cadence USBSSP DRD Driver")
> cc: stable@vger.kernel.org
> Signed-off-by: Pawel Laszczak <pawell@cadence.com>
> ---
> Changelog:
> v2:
> - replaced usleep_range with udelay
> - increased retry counter and decreased the udelay value
> 
>  drivers/usb/cdns3/cdnsp-gadget.c | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/cdns3/cdnsp-gadget.c b/drivers/usb/cdns3/cdnsp-gadget.c
> index 4824a10df07e..58650b7f4173 100644
> --- a/drivers/usb/cdns3/cdnsp-gadget.c
> +++ b/drivers/usb/cdns3/cdnsp-gadget.c
> @@ -547,6 +547,7 @@ int cdnsp_wait_for_cmd_compl(struct cdnsp_device *pdev)
>  	dma_addr_t cmd_deq_dma;
>  	union cdnsp_trb *event;
>  	u32 cycle_state;
> +	u32 retry = 10;
>  	int ret, val;
>  	u64 cmd_dma;
>  	u32  flags;
> @@ -578,8 +579,23 @@ int cdnsp_wait_for_cmd_compl(struct cdnsp_device *pdev)
>  		flags = le32_to_cpu(event->event_cmd.flags);
>  
>  		/* Check the owner of the TRB. */
> -		if ((flags & TRB_CYCLE) != cycle_state)
> +		if ((flags & TRB_CYCLE) != cycle_state) {
> +			/*
> +			 * Give some extra time to get chance controller
> +			 * to finish command before returning error code.
> +			 * Checking CMD_RING_BUSY is not sufficient because
> +			 * this bit is cleared to '0' when the Command
> +			 * Descriptor has been executed by controller
> +			 * and not when command completion event has
> +			 * be added to event ring.
> +			 */
> +			if (retry--) {
> +				udelay(20);
> +				continue;
> +			}
> +
>  			return -EINVAL;
> +		}
>  
>  		cmd_dma = le64_to_cpu(event->event_cmd.cmd_trb);
>  
> -- 
> 2.43.0
> 

-- 

Best regards,
Peter

RE: [PATCH v2] usb: cdnsp: Fix issue with detecting command completion event

[Pawel Laszczak]

>
>
>On 25-05-13 05:30:09, Pawel Laszczak wrote:
>> In some cases, there is a small-time gap in which CMD_RING_BUSY can be
>> cleared by controller but adding command completion event to event
>> ring will be delayed. As the result driver will return error code.
>> This behavior has been detected on usbtest driver (test 9) with
>> configuration including ep1in/ep1out bulk and ep2in/ep2out isoc
>> endpoint.
>> Probably this gap occurred because controller was busy with adding
>> some other events to event ring.
>> The CMD_RING_BUSY is cleared to '0' when the Command Descriptor has
>> been executed and not when command completion event has been added to
>> event ring.
>>
>> To fix this issue for this test the small delay is sufficient less
>> than 10us) but to make sure the problem doesn't happen again in the
>> future the patch introduces 10 retries to check with delay about 20us
>> before returning error code.
>
>Does the ./scripts/checkpatch.pl report warning if the delay time is 20us for
>udelay?

Yes, it is reported:
CHECK: usleep_range is preferred over udelay; ...

But only for checkpatch.pl  with --strict option

Pawel

>
>Peter
>>
>> Fixes: 3d82904559f4 ("usb: cdnsp: cdns3 Add main part of Cadence
>> USBSSP DRD Driver")
>> cc: stable@vger.kernel.org
>> Signed-off-by: Pawel Laszczak <pawell@cadence.com>
>> ---
>> Changelog:
>> v2:
>> - replaced usleep_range with udelay
>> - increased retry counter and decreased the udelay value
>>
>>  drivers/usb/cdns3/cdnsp-gadget.c | 18 +++++++++++++++++-
>>  1 file changed, 17 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/usb/cdns3/cdnsp-gadget.c
>> b/drivers/usb/cdns3/cdnsp-gadget.c
>> index 4824a10df07e..58650b7f4173 100644
>> --- a/drivers/usb/cdns3/cdnsp-gadget.c
>> +++ b/drivers/usb/cdns3/cdnsp-gadget.c
>> @@ -547,6 +547,7 @@ int cdnsp_wait_for_cmd_compl(struct cdnsp_device
>*pdev)
>>  	dma_addr_t cmd_deq_dma;
>>  	union cdnsp_trb *event;
>>  	u32 cycle_state;
>> +	u32 retry = 10;
>>  	int ret, val;
>>  	u64 cmd_dma;
>>  	u32  flags;
>> @@ -578,8 +579,23 @@ int cdnsp_wait_for_cmd_compl(struct cdnsp_device
>*pdev)
>>  		flags = le32_to_cpu(event->event_cmd.flags);
>>
>>  		/* Check the owner of the TRB. */
>> -		if ((flags & TRB_CYCLE) != cycle_state)
>> +		if ((flags & TRB_CYCLE) != cycle_state) {
>> +			/*
>> +			 * Give some extra time to get chance controller
>> +			 * to finish command before returning error code.
>> +			 * Checking CMD_RING_BUSY is not sufficient because
>> +			 * this bit is cleared to '0' when the Command
>> +			 * Descriptor has been executed by controller
>> +			 * and not when command completion event has
>> +			 * be added to event ring.
>> +			 */
>> +			if (retry--) {
>> +				udelay(20);
>> +				continue;
>> +			}
>> +
>>  			return -EINVAL;
>> +		}
>>
>>  		cmd_dma = le64_to_cpu(event->event_cmd.cmd_trb);
>>
>> --
>> 2.43.0
>>
>
>--
>
>Best regards,
>Peter

Re: [PATCH v2] usb: cdnsp: Fix issue with detecting command completion event

[Peter Chen (CIX)]

On 25-05-13 05:30:09, Pawel Laszczak wrote:
> In some cases, there is a small-time gap in which CMD_RING_BUSY
> can be cleared by controller but adding command completion event
> to event ring will be delayed. As the result driver will return
> error code.
> This behavior has been detected on usbtest driver (test 9) with
> configuration including ep1in/ep1out bulk and ep2in/ep2out isoc
> endpoint.
> Probably this gap occurred because controller was busy with adding
> some other events to event ring.
> The CMD_RING_BUSY is cleared to '0' when the Command Descriptor
> has been executed and not when command completion event has been
> added to event ring.
> 
> To fix this issue for this test the small delay is sufficient
> less than 10us) but to make sure the problem doesn't happen again
> in the future the patch introduces 10 retries to check with delay
> about 20us before returning error code.
> 
> Fixes: 3d82904559f4 ("usb: cdnsp: cdns3 Add main part of Cadence USBSSP DRD Driver")
> cc: stable@vger.kernel.org
> Signed-off-by: Pawel Laszczak <pawell@cadence.com>

Acked-by: Peter Chen <peter.chen@kernel.org>

Peter
> ---
> Changelog:
> v2:
> - replaced usleep_range with udelay
> - increased retry counter and decreased the udelay value
> 
>  drivers/usb/cdns3/cdnsp-gadget.c | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/cdns3/cdnsp-gadget.c b/drivers/usb/cdns3/cdnsp-gadget.c
> index 4824a10df07e..58650b7f4173 100644
> --- a/drivers/usb/cdns3/cdnsp-gadget.c
> +++ b/drivers/usb/cdns3/cdnsp-gadget.c
> @@ -547,6 +547,7 @@ int cdnsp_wait_for_cmd_compl(struct cdnsp_device *pdev)
>  	dma_addr_t cmd_deq_dma;
>  	union cdnsp_trb *event;
>  	u32 cycle_state;
> +	u32 retry = 10;
>  	int ret, val;
>  	u64 cmd_dma;
>  	u32  flags;
> @@ -578,8 +579,23 @@ int cdnsp_wait_for_cmd_compl(struct cdnsp_device *pdev)
>  		flags = le32_to_cpu(event->event_cmd.flags);
>  
>  		/* Check the owner of the TRB. */
> -		if ((flags & TRB_CYCLE) != cycle_state)
> +		if ((flags & TRB_CYCLE) != cycle_state) {
> +			/*
> +			 * Give some extra time to get chance controller
> +			 * to finish command before returning error code.
> +			 * Checking CMD_RING_BUSY is not sufficient because
> +			 * this bit is cleared to '0' when the Command
> +			 * Descriptor has been executed by controller
> +			 * and not when command completion event has
> +			 * be added to event ring.
> +			 */
> +			if (retry--) {
> +				udelay(20);
> +				continue;
> +			}
> +
>  			return -EINVAL;
> +		}
>  
>  		cmd_dma = le64_to_cpu(event->event_cmd.cmd_trb);
>  
> -- 
> 2.43.0
> 

-- 

Best regards,
Peter