From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
Subject: Re: [RFC, v3 9/9] media: platform: Add Mediatek ISP P1 shared memory
 device
Date: Fri, 26 Jul 2019 00:41:16 -0700
Message-ID: <20190726074116.GA19745@infradead.org>
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To: Tomasz Figa <tfiga-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
Cc: devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Sean Cheng =?utf-8?B?KOmEreaYh+W8mCk=?= <sean.cheng-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org>, Mauro Carvalho Chehab <mchehab-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Rynn Wu =?utf-8?B?KOWQs+iCsuaBqSk=?= <rynn.wu-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org>, Linux Media Mailing List <linux-media-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, srv_heupstream <srv_heupstream-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org>, Rob Herring <robh-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Ryan Yu =?utf-8?B?KOS9meWtn+S/rik=?= <ryan.yu-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org>, Frankie Chiu =?utf-8?B?KOmCseaWh+WHsSk=?= <frankie.chiu-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org>, Hans Verkuil <hverkuil-qWit8jRvyhVmR6Xm/wNWPw@public.gmane.org>, Jungo Lin <jungo.lin-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org>, Sj Huang <sj.huang-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org>, "moderated list:ARM/Mediatek SoC support" <linux-mediatek-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org>, Laurent Pinchart <laurent.pinchart-ryLnwIuWjnjg/C1BVhZhaw@public.gmane.org>, ddavenport-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org, Frederic Chen =?utf-8?B?KOmZs+S/iuWFgyk=?= <frederic.chen-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org>, list-Y9sIeH5OGRo@public.gmane.org:IOMMU DRIVERS <iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>,
 Joerg Roedel <jo
List-Id: devicetree@vger.kernel.org

On Fri, Jul 26, 2019 at 02:15:14PM +0900, Tomasz Figa wrote:
> Could you try dma_get_sgtable() with the SCP struct device and then
> dma_map_sg() with the P1 struct device?

Please don't do that.  dma_get_sgtable is a pretty broken API (see
the common near the arm implementation) and we should not add more
users of it.  If you want a piece of memory that can be mapped to
multiple devices allocate it using alloc_pages and then just map
it to each device.