linux-kernel - Re: [PATCH 1/2] usb: musb: Fix DMA for host mode

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Date:	Thu, 4 Feb 2016 19:44:24 +0300
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Joshua Henderson <joshua.henderson@...rochip.com>,
	linux-kernel@...r.kernel.org
Cc:	Cristian Birsan <cristian.birsan@...rochip.com>,
	Felipe Balbi <balbi@...com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-usb@...r.kernel.org
Subject: Re: [PATCH 1/2] usb: musb: Fix DMA for host mode

On 02/02/2016 04:24 PM, Sergei Shtylyov wrote:

>> From: Cristian Birsan <cristian.birsan@...rochip.com>
>>
>> Commit ac33cdb166811223cc (usb: musb: Remove ifdefs for musb_host_rx in
>> musb_host.c part5) introduces a problem setting DMA host mode.
>
>     scripts/checkpatch.pl now enforces certain commit citing style, yours
> doesn't quite match it.
>
>> This fixes the done condition that advances the musb schedule. Without this
>> patch the the msub_advance_schedule() is called immediately after receiving an
>> endpoint rx interrupt without waiting for the dma transfer to complete. As a
>> consequence when the dma complete interrupt arrives the in_qh member of hw_ep
>> is already null an the musb_host_rx() exits on !urb error case.
>>
>> Signed-off-by: Cristian Birsan <cristian.birsan@...rochip.com>
>> Signed-off-by: Joshua Henderson <joshua.henderson@...rochip.com>
>> ---
>>   drivers/usb/musb/musb_host.c |    5 +++--
>>   1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/usb/musb/musb_host.c b/drivers/usb/musb/musb_host.c
>> index 795a45b..3fdc99b 100644
>> --- a/drivers/usb/musb/musb_host.c
>> +++ b/drivers/usb/musb/musb_host.c
>> @@ -1825,6 +1825,7 @@ void musb_host_rx(struct musb *musb, u8 epnum)
>>       u16            rx_csr, val;
>>       bool            iso_err = false;
>>       bool            done = false;
>> +    int            ret;
>>       u32            status;
>>       struct dma_channel    *dma;
>>       unsigned int sg_flags = SG_MITER_ATOMIC | SG_MITER_TO_SG;
>> @@ -2003,10 +2004,10 @@ void musb_host_rx(struct musb *musb, u8 epnum)
>>                   qh->offset,
>>                   urb->transfer_buffer_length);
>>
>> -            done = musb_rx_dma_in_inventra_cppi41(c, hw_ep, qh,
>> +            ret = musb_rx_dma_in_inventra_cppi41(c, hw_ep, qh,
>>                                     urb, xfer_len,
>>                                     iso_err);
>> -            if (done)
>> +            if (ret)
>
>     Hm, does that really fix anything?

    Looking again, I got the idea. However, there's no dire need for the new 
variable...
    (Handling Inventra and CPPI 4.1 DMA in the same code looks fishy. Too bad 
I wasn't able to push the CPPI 4.1 drivers myself.)

MBR, Sergei