Re: [PATCH 4/4] usb: musb: musb_cppi41: Workaround dma stall issue during teardown

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On 01/09/2017 07:34 PM, Sergei Shtylyov wrote:
> Hello!
> 
> On 01/09/2017 07:39 PM, Alexandre Bailon wrote:
> 
>> The dma may hung up if a teardown is initiated while an endpoint is still
> 
>    The DMA may hang up...
> 
>> active (Advisory 2.3.27 of da8xx errata).
>> To workaround this issue, add a delay before to initiate the teardown.
>>
>> Signed-off-by: Alexandre Bailon <abailon@xxxxxxxxxxxx>
> [...]
>> diff --git a/drivers/usb/musb/musb_cppi41.c
>> b/drivers/usb/musb/musb_cppi41.c
>> index 1636385..8fdbc17 100644
>> --- a/drivers/usb/musb/musb_cppi41.c
>> +++ b/drivers/usb/musb/musb_cppi41.c
>> @@ -547,6 +547,10 @@ static int cppi41_dma_channel_abort(struct
>> dma_channel *channel)
>>          }
>>      }
>>
>> +    /* DA8xx Advisory 2.3.27: wait 250 ms before to start the
>> teardown */
>> +    if (musb->io.quirks & MUSB_DA8XX)
>> +        mdelay(250);
> 
>    This is a horrible workaround, not even msleep()...
Indeed, that's a bad workaround but have not found a better one.
cppi41_dma_channel_abort() is called from atomic context,
so we can't use msleep().
And update the musb driver to call cppi41_dma_channel_abort()
from process context would require too many changes.

Best Regards,
Alexandre
> 
> [...]
> 
> MBR, Sergei
> 

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