Re: [PATCH v3 4/5] usb: musb: musb_cppi41: Workaround DMA stall issue during teardown

[Alexandre Bailon <abailon-rdvid1DuHRBWk0Htik3J/w@public.gmane.org>]

On 01/19/2017 05:56 PM, Tony Lindgren wrote:
> * Alexandre Bailon <abailon-rdvid1DuHRBWk0Htik3J/w@public.gmane.org> [170119 06:09]:
>> The DMA may hung up if a teardown is initiated while an endpoint is still
>> 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-rdvid1DuHRBWk0Htik3J/w@public.gmane.org>
>> ---
>>  drivers/usb/musb/da8xx.c       | 2 +-
>>  drivers/usb/musb/musb_core.h   | 1 +
>>  drivers/usb/musb/musb_cppi41.c | 4 ++++
>>  3 files changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/usb/musb/da8xx.c b/drivers/usb/musb/da8xx.c
>> index 5f50a78..8c9850c 100644
>> --- a/drivers/usb/musb/da8xx.c
>> +++ b/drivers/usb/musb/da8xx.c
>> @@ -483,7 +483,7 @@ da8xx_dma_controller_create(struct musb *musb, void __iomem *base)
>>  #endif
>>  
>>  static const struct musb_platform_ops da8xx_ops = {
>> -	.quirks		= MUSB_INDEXED_EP | MUSB_DMA_CPPI41,
>> +	.quirks		= MUSB_INDEXED_EP | MUSB_DMA_CPPI41 | MUSB_DA8XX,
>>  	.init		= da8xx_musb_init,
>>  	.exit		= da8xx_musb_exit,
>>  
>> diff --git a/drivers/usb/musb/musb_core.h b/drivers/usb/musb/musb_core.h
>> index ade902e..d129278 100644
>> --- a/drivers/usb/musb/musb_core.h
>> +++ b/drivers/usb/musb/musb_core.h
>> @@ -172,6 +172,7 @@ struct musb_io;
>>   */
>>  struct musb_platform_ops {
>>  
>> +#define MUSB_DA8XX		BIT(7)
>>  #define MUSB_DMA_UX500		BIT(6)
>>  #define MUSB_DMA_CPPI41		BIT(5)
>>  #define MUSB_DMA_CPPI		BIT(4)
>> diff --git a/drivers/usb/musb/musb_cppi41.c b/drivers/usb/musb/musb_cppi41.c
>> index 1fe7eae..d371d05 100644
>> --- a/drivers/usb/musb/musb_cppi41.c
>> +++ b/drivers/usb/musb/musb_cppi41.c
>> @@ -554,6 +554,10 @@ 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);
>> +
>>  	tdbit = 1 << cppi41_channel->port_num;
>>  	if (is_tx)
>>  		tdbit <<= 16;
> 
> How about replace the do while loop calling  dmaengine_terminate_all() with
> deferred work doing that?
That would be great but I don't know how hard to would be to do it.
Right after the teardown, we may have to queue a new request.
But we must be sure that the teardown has completed before to start
a new transfer. And because it happen in atomic section, we must also
defer it.
> 
> That way it's more generic as it seems there's no hurry doing that
> after the musb registers are cleared. That would also allow getting rid of
> the two current udelay() calls there that also seems nasty.
> 
> Regards,
> 
> Tony
> 
Regards,
Alexandre
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