linux-kernel - Re: [PATCH 1/3] ata: sata_dwc_460ex: use "dmas" DT property to find dma channel

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Date:	Sat, 19 Dec 2015 17:19:53 +0000
From:	Måns Rullgård <mans@...sr.com>
To:	Julian Margetson <runaway@...dw.ms>
Cc:	Andy Shevchenko <andy.shevchenko@...il.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Tejun Heo <tj@...nel.org>, linux-ide@...r.kernel.org,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] ata: sata_dwc_460ex: use "dmas" DT property to find dma channel

Julian Margetson <runaway@...dw.ms> writes:

> On 12/19/2015 1:05 PM, Måns Rullgård wrote:
>> Andy Shevchenko <andy.shevchenko@...il.com> writes:
>>
>>> On Sat, Dec 19, 2015 at 5:40 PM, Måns Rullgård <mans@...sr.com> wrote:
>>>
>>>> OK, I've found something.  The dma setup errors are benign, caused by
>>>> the driver calling dmaengine_prep_slave_sg() even for non-dma
>>>> operations.
>>> I suppose the following is a quick fix to avoid preparing descriptor
>>> for non-DMA operations (not tested anyhow)
>>>
>>> a/drivers/ata/sata_dwc_460ex.c
>>> +++ b/drivers/ata/sata_dwc_460ex.c
>>> @@ -1041,6 +1041,9 @@ static void sata_dwc_qc_prep_by_tag(struct
>>> ata_queued_cmd *qc, u8 tag)
>>>                  __func__, ap->port_no, get_dma_dir_descript(qc->dma_dir),
>>>                   qc->n_elem);
>>>
>>> +       if (!is_slave_direction(qc->dma_dir))
>>> +               return;
>>> +
>>>          desc = dma_dwc_xfer_setup(qc);
>>>          if (!desc) {
>>>                  dev_err(ap->dev, "%s: dma_dwc_xfer_setup returns NULL\n",
>> I already have a better patch sitting here.
>>
>>>> The real error is the lock recursion that's reported
>>>> later.  I wasn't seeing it since I was running a UP non-preempt kernel.
>>>> With lock debugging enabled, I get the same error.  This patch should
>>>> fix it.
>>>> -       spin_lock_irqsave(&ap->host->lock, flags);
>>>>          hsdevp->cmd_issued[tag] = cmd_issued;
>>>> -       spin_unlock_irqrestore(&ap->host->lock, flags);
>>>> +
>>> This will create a second empty line, though I don't care it is so minor.
>> The patch leaves one blank line before the following block comment.  I
>> think it looks better that way.
>>
>
> Still can't get the patch applied .

Sorry, didn't realise it conflicted with an intervening patch I had in
my tree.  Try this one.

-- 
Måns Rullgård

View attachment "0001-ata-sata_dwc_460ex-remove-incorrect-locking.patch" of type "text/x-diff" (1374 bytes)