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[ Upstream commit99e360442f] The drm_display_mode_to_videomode() does not populate DISPLAY_FLAGS_DE_LOW or DISPLAY_FLAGS_PIXDATA_NEGEDGE flags in struct videomode. Therefore, no matter what polarity the next bridge or display might require, these flags are never set, and thus the LTDC GCR_DEPOL and GCR_PCPOL bits are never set and the LTDC behaves as if both DISPLAY_FLAGS_PIXDATA_POSEDGE and DISPLAY_FLAGS_DE_HIGH were always set. The fix for this problem is taken almost verbatim from MXSFB driver. In case there is a bridge attached to the LTDC, the bridge might have extra polarity requirements, so extract bus_flags from the bridge and use them for LTDC configuration. Otherwise, extract bus_flags from the connector, which is the display. Fixes:b759012c5f("drm/stm: Add STM32 LTDC driver") Signed-off-by: Marek Vasut <marex@denx.de> Signed-off-by: Yannick Fertre <yannick.fertre@st.com> Cc: Alexandre Torgue <alexandre.torgue@st.com> Cc: Antonio Borneo <antonio.borneo@st.com> Cc: Benjamin Gaignard <benjamin.gaignard@st.com> Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com> Cc: Philippe Cornu <philippe.cornu@st.com> Cc: Sam Ravnborg <sam@ravnborg.org> Cc: Vincent Abriou <vincent.abriou@st.com> Cc: Yannick Fertre <yannick.fertre@st.com> Cc: linux-arm-kernel@lists.infradead.org Cc: linux-stm32@st-md-mailman.stormreply.com To: dri-devel@lists.freedesktop.org Tested-by: Yannick Fertre <yannick.fertre@foss.st.com> Signed-off-by: Philippe Cornu <philippe.cornu@foss.st.com> Link: https://patchwork.freedesktop.org/patch/msgid/20210127110756.125570-1-marex@denx.de Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.