linux-kernel - Re: [PATCH v1] drm/rockchip: Set VOP for the DRM DMA device

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Message-ID: <3705026.LM0AJKV5NW@phil>
Date: Thu, 23 Oct 2025 08:56:00 +0200
From: Heiko Stuebner <heiko@...ech.de>
To: Sandy Huang <hjc@...k-chips.com>, Andy Yan <andy.yan@...k-chips.com>,
 Robin Murphy <robin.murphy@....com>,
 Sebastian Reichel <sebastian.reichel@...labora.com>,
 Daniel Stone <daniels@...labora.com>,
 Dmitry Osipenko <dmitry.osipenko@...labora.com>
Cc: kernel@...labora.com, linux-arm-kernel@...ts.infradead.org,
 linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org,
 dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v1] drm/rockchip: Set VOP for the DRM DMA device

Hi Dmitry,

Am Mittwoch, 22. Oktober 2025, 18:19:48 Mitteleuropäische Sommerzeit schrieb Dmitry Osipenko:
> Use VOP for DMA operations performed by DRM core. Rockchip DRM driver
> is backed by a virtual device that isn't IOMMU-capable, while VOP is the
> actual display controller device backed by IOMMU. Fixes "swiotlb buffer
> is full" warning messages originated from GEM prime code paths.
> 
> Note, that backporting is non-trivial as this depends on 143ec8d3f9396
> ("drm/prime: Support dedicated DMA device for dma-buf imports"), which
> landed in v6.16 and 421be3ee36a4 ("drm/rockchip: Refactor IOMMU
> initialisation"), which landed in v5.19.
> 
> Reported-by: Daniel Stone <daniels@...labora.com>
> Fixes: 2048e3286f34 ("drm: rockchip: Add basic drm driver")
> Cc: stable@...r.kernel.org # v6.16+
> Reviewed-by: Sebastian Reichel <sebastian.reichel@...labora.com>
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@...labora.com>

just a process remark for now. This v1 so it definitly shouldn't come
with any Reviewed-by-s pre-applied, because this should happen in public.

It's not a huge issue here, because I do trust the people involved (you,
Sebastian, Daniel) and the change is small enough, but please for future
changes, let Review happen on the list, not on private channels.


Will look at the change itself when back home.


Thanks
Heiko