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From: Linus Walleij <linus.walleij@linaro.org>
To: David Hildenbrand <david@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux-MM <linux-mm@kvack.org>, Joel Stanley <joel@jms.id.au>,
	David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
	Andrew Jeffery <andrew@aj.id.au>,
	Lucas Stach <l.stach@pengutronix.de>,
	Russell King <linux+etnaviv@armlinux.org.uk>,
	Christian Gmeiner <christian.gmeiner@gmail.com>,
	Mike Rapoport <rppt@kernel.org>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
	Michal Simek <michal.simek@xilinx.com>,
	Masahiro Yamada <masahiroy@kernel.org>,
	Randy Dunlap <rdunlap@infradead.org>,
	Peter Collingbourne <pcc@google.com>,
	linux-aspeed <linux-aspeed@lists.ozlabs.org>,
	dri-devel <dri-devel@lists.freedesktop.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	The etnaviv authors <etnaviv@lists.freedesktop.org>,
	Linux Fbdev development list <linux-fbdev@vger.kernel.org>
Subject: Re: [PATCH v1 2/2] drivers/gpu/drm: don't select DMA_CMA or CMA from aspeed or etnaviv
Date: Thu, 8 Apr 2021 23:45:23 +0200	[thread overview]
Message-ID: <CACRpkdbMLBzG_Q=-XzjsWvpofHyRv7sdB697mHLaRu4F=+GC-g@mail.gmail.com> (raw)
In-Reply-To: <2ef3b65c-c0ef-7bbe-0e05-39ee8f2bae48@redhat.com>

On Thu, Apr 8, 2021 at 6:44 PM David Hildenbrand <david@redhat.com> wrote:

> > drivers/gpu/drm/mcde/Kconfig
> > drivers/gpu/drm/pl111/Kconfig
> > drivers/gpu/drm/tve200/Kconfig
>
> I was assuming these are "real" dependencies. Will it also work without
> DMA_CMA?

It will mostly work but that is only because the reservations are
mostly contiguous anyway because they are done early and
are small. The hardware requires contiguous buffers in all
three cases. I'm not sure I always got it right.

> > certainly needs this as well, and pretty much anything that is
> > selecting DRM_KMS_CMA_HELPER or
> > DRM_GEM_CMA_HELPER "wants" DMA_CMA.
>
> "wants" as in "desires to use but can life without" or "wants" as in
> "really needs it". ?

I don't know the exact semantics of using DRM_KMS_CMA*
without actually using DMA_CMA. I suspect small allocations
will be contiguous and big allocations will start to fragment?
but it's just my guess. I guess "really need it"?

Yours,
Linus Walleij

  parent reply	other threads:[~2021-04-08 21:45 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-08  9:20 [PATCH v1 0/2] drivers: don't select DMA_CMA or CMA David Hildenbrand
2021-04-08  9:20 ` [PATCH v1 1/2] drivers/video/fbdev: don't select DMA_CMA David Hildenbrand
2021-04-08  9:56   ` Mike Rapoport
2021-04-08  9:20 ` [PATCH v1 2/2] drivers/gpu/drm: don't select DMA_CMA or CMA from aspeed or etnaviv David Hildenbrand
2021-04-08  9:56   ` Mike Rapoport
2021-04-08  9:57     ` David Hildenbrand
2021-04-08 10:20   ` Arnd Bergmann
2021-04-08 10:27     ` David Hildenbrand
2021-04-08 10:36       ` David Hildenbrand
2021-04-08 10:44       ` Arnd Bergmann
2021-04-08 11:00         ` David Hildenbrand
2021-04-08 11:44           ` Arnd Bergmann
2021-04-08 12:00             ` David Hildenbrand
2021-04-08 12:12               ` Arnd Bergmann
2021-04-08 12:49               ` Linus Walleij
2021-04-08 13:19                 ` Arnd Bergmann
2021-04-09  8:07                   ` David Hildenbrand
2021-04-08 16:44                 ` David Hildenbrand
2021-04-08 20:29                   ` Arnd Bergmann
2021-04-09  8:09                     ` David Hildenbrand
2021-04-08 21:45                   ` Linus Walleij [this message]
2021-04-08 11:38     ` Daniel Vetter
2021-04-08 16:46       ` Jason Gunthorpe

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