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

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Message-ID: <yw1x60zs7g40.fsf@unicorn.mansr.com>
Date:	Mon, 21 Dec 2015 01:19:43 +0000
From:	Måns Rullgård <mans@...sr.com>
To:	Andy Shevchenko <andy.shevchenko@...il.com>
Cc:	Julian Margetson <runaway@...dw.ms>,
	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

Andy Shevchenko <andy.shevchenko@...il.com> writes:

> On Sun, Dec 20, 2015 at 10:17 PM, Andy Shevchenko
> <andy.shevchenko@...il.com> wrote:
>> On Sun, Dec 20, 2015 at 8:49 PM, Måns Rullgård <mans@...sr.com> wrote:
>>> Julian Margetson <runaway@...dw.ms> writes:
>>>> On 12/20/2015 1:11 PM, Måns Rullgård wrote:
>>>>> Julian Margetson <runaway@...dw.ms> writes:
>>
>>>> [   48.769671] ata3.00: failed command: READ FPDMA QUEUED
>>>
>>> Well, that didn't help.  I still think it's part of the problem, but
>>> something else must be wrong as well.  The various Master Select fields
>>> look like a good place to start.
>>
>> Master number (which is here would be either 1 or 0) should not affect
>> as long as they are connected to the same AHB bus (I would be
>> surprised if they are not).
>>
>>>  Also, the manual says the LLP_SRC_EN
>>> and LLP_DST_EN flags should be cleared on the last in a chain of blocks.
>>> The old sata_dwc driver does this whereas dw_dma does not.
>>
>> Easy to fix, however I can't get how it might affect.
>>
>>> It might be worthwhile to try reverting drivers/ata/sata_dwc_460ex.c to
>>> v4.0 (leaving the rest at 4.4-rc5) just to make sure that's a good
>>> reference.  I've verified that this builds.
>>
>> It would be nice.
>>
>> I noticed thanks to DWC_PARAMS that burst size is hardcoded to 32
>> items on this board, however registers for SATA program it to 64. I
>> remember that I got no interrupt when I programmed transfer width
>> wrongly (64 bits against 32 bits) when I ported dw_dmac to be used on
>> Intel SoCs.
>
> One more thing, I have a patch to monitor DMA IO, we may check what
> exactly the values are written / read  in DMA. I can share it
> tomorrow.
>
> P.S. I also noticed that original driver enables interrupt per each
> block

And then ignores all but the transfer complete interrupt.

> and sets protection control bits.

With no indication what the value it sets is supposed to mean.

-- 
Måns Rullgård
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