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 14:56:15 -0400
From:	Julian Margetson <runaway@...dw.ms>
To:	Måns Rullgård <mans@...sr.com>
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@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] ata: sata_dwc_460ex: use "dmas" DT property to find
 dma channel

On 12/19/2015 1:19 PM, Måns Rullgård wrote:
> 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.
>


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