Hi Marek,
On Tue, 7 Jan 2020 10:11:43 +0100
Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> wrote:
> Hi Boris,
>
> Sorry, for the late reply, I've just got back from my prolonged Chrismas
> holidays.
>
> On 27.12.2019 15:41, Boris Brezillon wrote:
> > Commit 05193dc38197 ("drm/bridge: Make the bridge chain a double-linked
> > list") patched the bridge chain logic to use a double-linked list instead
> > of a single-linked list. This change induced changes to the Exynos driver
> > which was manually resetting the encoder->bridge element to NULL to
> > control the enable/disable sequence of the bridge chain. During this
> > conversion, 2 bugs were introduced:
> >
> > 1/ list_splice() was used to move chain elements to our own internal
> > chain, but list_splice() does not reset the source list to an empty
> > state, leading to unexpected bridge hook calls when
> > drm_bridge_chain_xxx() helpers were called by the core. Replacing
> > the list_splice() call by list_splice_init() fixes this problem.
> >
> > 2/ drm_bridge_chain_xxx() helpers operate on the
> > bridge->encoder->bridge_chain list, which is now empty. When the
> > helper uses list_for_each_entry_reverse() we end up with no operation
> > done which is not what we want. But that's even worse when the helper
> > uses list_for_each_entry_from(), because in that case we end up in
> > an infinite loop searching for the list head element which is no
> > longer encoder->bridge_chain but exynos_dsi->bridge_chain. To address
> > that problem we stop using the bridge chain helpers and call the
> > hooks directly.
> >
> > Reported-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> > Fixes: 05193dc38197 ("drm/bridge: Make the bridge chain a double-linked list")
> > Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
>
> Works fine on Exynos5250-based Arndale board.
>
> Tested-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Thanks for testing, but can you also add your R-b (I need it to make
dim happy)? While you're at it, maybe you can review patch 2 (it's very
similar to this patch).
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