From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Luis R. Rodriguez" <mcgrof@kernel.org>
Subject: Do Qualcomm drivers use DMA buffers for request_firmware_into_buf()?
Date: Wed, 6 Jun 2018 22:32:57 +0200
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To: Andy Gross <andy.gross@linaro.org>, David Brown <david.brown@linaro.org>, Bjorn Andersson <bjorn.andersson@linaro.org>, Hans de Goede <hdegoede@redhat.com>, Michal Hocko <mhocko@kernel.org>, Andrew Morton <akpm@linux-foundation.org>, Rik van Riel <riel@surriel.com>, Laura Abbott <labbott@redhat.com>, Vlastimil Babka <vbabka@suse.cz>
Cc: dmitry.torokhov@gmail.com, Matt Fleming <matt@codeblueprint.co.uk>, Will Deacon <will.deacon@arm.com>, platform-driver-x86@vger.kernel.org, David Howells <dhowells@redhat.com>, Peter Jones <pjones@redhat.com>, mcgrof@kernel.org, "H . Peter Anvin" <hpa@zytor.com>, "open list:ANDROID DRIVERS" <devel@driverdev.osuosl.org>, nbroeking@me.com, Jonathan Corbet <corbet@lwn.net>, x86@kernel.org, Arve =?iso-8859-1?B?SGr4bm5lduVn?= <arve@android.com>, Ingo Molnar <mingo@redhat.com>, Darren Hart <dvhart@infradead.org>, Mimi Zohar <zohar@linux.vnet.ibm.com>, Arend Van Spriel <arend.vanspriel@broadcom.com>, Todd Kjos <tkjos@android.com>, Kees Cook <keescook@chromium.org>, linux-efi <linux-efi@vger.kernel.org>, linux-arm-msm@vger.kernel.org, Torsten Duwe <duwe@suse.de>, Josh Triplett <josh@joshtriplett.org>, Chris Wright <chrisw@sous-sol.org>, Andy Lutomirski <luto@kernel.org>, Thomas
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On Fri, Jun 01, 2018 at 09:23:46PM +0200, Luis R. Rodriguez wrote:
> On Tue, May 08, 2018 at 03:38:05PM +0000, Luis R. Rodriguez wrote:
> > On Fri, May 04, 2018 at 12:44:37PM -0700, Martijn Coenen wrote:
> > > 
> > > I think the Qualcomm folks owning this (Andy, David, Bjorn, already
> > > cc'd here) are better suited to answer that question.
> > 
> > Andy, David, Bjorn?
> 
> Andy, David, Bjorn?

A month now with no answer...

Perhaps someone who has this hardware can find out empirically for us, as
follows (mm folks is this right?):

page = virt_to_page(address);
if (!page)
   fail closed...
if (page_zone(page) == ZONE_DMA || page_zone(page) == ZONE_DMA32)
	this is a DMA buffer
else
	not DMA!

Note that when request_firmware_into_buf() was being reviewed Mimi had asked back
in 2016 [0] that if a DMA buffer was going to be used READING_FIRMWARE_DMA should be
used otherwise READING_FIRMWARE_PREALLOC_BUFFER was fine.

If it is a DMA buffer *now*, why / how did this change?

[0] https://patchwork.kernel.org/patch/9074611/

  Luis