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

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Date:	Mon, 21 Dec 2015 21:06:23 +0000
From:	Måns Rullgård <mans@...sr.com>
To:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:	Andy Shevchenko <andy.shevchenko@...il.com>,
	Julian Margetson <runaway@...dw.ms>, 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 <andriy.shevchenko@...ux.intel.com> writes:

>> > 4. CHECK: PROTCTL bit (documentation says that recommended value is
>> > 0x01)
>> 
>> Any idea what the value of 0x3 used by the old sata driver means?
>> Presumably that's decided by the bus.
>
> Nope, documentation says that it is direct representation of hprot[3:1]
> wires on the master interface. Also it refers to AMBA spec, so, if you
> have access to AMBA spec I think we might get it from there.

That's assuming AMCC didn't change something.

>> > 5. CHECK: Other bits in CFG register (FIFO_MODE, FCMODE)
>> > 6. CHECK: Block interrupts vs. one interrupt at the end of block
>> > chain
>> > (Måns, I missed how any of them is ignored)
>> 
>> The interrupt handler looks at the StatusTfr and StatusErr registers
>> and ignores StatusBlock.
>
> I have to refresh my memory, since BLOCK interrupts should be enabled
> (unmasked) separately. I have forgotten which type of interrupt is
> generated in this case, BLOCK, or XFER after each block, or only one
> XFER at the last block (LLP.LOC = 0) and BLOCK are ignored. So, will
> check later.

I interpreted the, admittedly a bit vague, documentation as meaning
BLOCK interrupts are signalled after each block and XFER interrupts
after the last block.

>> > 7. AR: Test everything on Intel SoCs such as Baytrail, CherryTrail,
>> > etc (SPI, UART, dmatest), AVR32 (MMC, dmatest), PPC 460EX (Onboard
>> > SATA)
>> 
>> I can test on AVR32.  That is as far as I know the only system I have
>> with this DMA engine.
>
> If you have Intel Haswell, BayTrail, Braswell, CherryTrail, Broadwell,
> you have it as well as long you have LPSS block there. (Most of them
> are Atoms).

I don't have any of those (or any Atom hardware).

-- 
Måns Rullgård
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