From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Niyas Sait <niyas.sait@linaro.org>
Cc: mika.westerberg@linux.intel.com, vkoul@kernel.org,
dmaengine@vger.kernel.org, linux-acpi@vger.kernel.org,
Sudeep.Holla@arm.com, Souvik.Chakravarty@arm.com,
Sunny.Wang@arm.com, lorenzo.pieralisi@linaro.org,
bob.zhang@cixtech.com, fugang.duan@cixtech.com
Subject: Re: [RFC v1 1/1] Refactor ACPI DMA to support platforms without shared info descriptor in CSRT
Date: Wed, 22 Mar 2023 11:34:39 +0200 [thread overview]
Message-ID: <ZBrLr4QDdZpgs3RV@smile.fi.intel.com> (raw)
In-Reply-To: <6e90881b-ba24-7f5a-e80d-1ae7fc9d9382@linaro.org>
On Wed, Mar 22, 2023 at 07:56:11AM +0000, Niyas Sait wrote:
> On 21/03/2023 17:53, Andy Shevchenko wrote:
>
> > can_we_avoid_long_name_of_the_functions_please() ?
>
> Sure, will do that.
>
> > Also is this renaming is a must?
>
> It is not a must. I considered the existing method with shared info
> as a special case as it uses non standard descriptors from CSRT table
> and introduced the new function to handle it.
>
> > Btw, what is the real argument of not using this table?
> >
> > Yes, I know that this is an MS extension, but why ARM needs something else and
> > why even that is needed at all? CSRT is only for the _shared_ DMA resources
> > and I think most of the IPs nowadays are using private DMA engines (or
> > semi-private when driver based on ID can know which channel services which
> > device).
>
> The issue is that shared info descriptor is not part of CSRT definition [1]
> and I think it is not standardized or documented anywhere.
>
> I was specifically looking at NXP I.MX8MP platform and the DMA lines for
> devices are specified using FixedDMA resource descriptor. I think other Arm
> platforms like RPi have similar requirement.
Perhaps, but my question is _why_ is it so?
I.o.w. what is the technical background for this solution.
> [1] https://uefi.org/sites/default/files/resources/CSRT%20v2.pdf
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2023-03-22 9:34 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-21 16:02 [RFC v1 1/1] Refactor ACPI DMA to support platforms without shared info descriptor in CSRT Niyas Sait
2023-03-21 17:53 ` Andy Shevchenko
2023-03-21 17:56 ` Andy Shevchenko
2023-03-22 7:56 ` Niyas Sait
2023-03-22 9:34 ` Andy Shevchenko [this message]
2023-03-22 9:38 ` Andy Shevchenko
2023-03-22 12:00 ` Niyas Sait
2023-03-22 14:32 ` Andy Shevchenko
2023-03-22 15:51 ` Niyas Sait
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