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Date: Tue, 4 Jun 2024 16:44:03 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
To: noralf@tronnes.org
Cc: Neil Armstrong <neil.armstrong@linaro.org>, 
	Jessica Zhang <quic_jesszhan@quicinc.com>, Sam Ravnborg <sam@ravnborg.org>, 
	David Airlie <airlied@gmail.com>, Daniel Vetter <daniel@ffwll.ch>, 
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>, Maxime Ripard <mripard@kernel.org>, 
	Thomas Zimmermann <tzimmermann@suse.de>, Rob Herring <robh@kernel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>, Conor Dooley <conor+dt@kernel.org>, 
	David Lechner <david@lechnology.com>, dri-devel@lists.freedesktop.org, devicetree@vger.kernel.org, 
	linux-kernel@vger.kernel.org, Kamlesh Gurudasani <kamlesh.gurudasani@gmail.com>, 
	Tommaso Merciai <tommaso.merciai@amarulasolutions.com>
Subject: Re: [PATCH v4 3/5] drm/mipi-dbi: Make bits per word configurable for
 pixel transfers
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References: <20240604-panel-mipi-dbi-rgb666-v4-0-d7c2bcb9b78d@tronnes.org>
 <20240604-panel-mipi-dbi-rgb666-v4-3-d7c2bcb9b78d@tronnes.org>
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In-Reply-To: <20240604-panel-mipi-dbi-rgb666-v4-3-d7c2bcb9b78d@tronnes.org>

On Tue, Jun 04, 2024 at 03:20:30PM +0200, Noralf Tr?nnes via B4 Relay wrote:
> From: Noralf Tr?nnes <noralf@tronnes.org>
> 
> MIPI DCS write/set commands have 8 bit parameters except for the
> write_memory commands where it depends on the pixel format.
> drm_mipi_dbi does currently only support RGB565 which is 16-bit and it
> has to make sure that the pixels enters the SPI bus in big endian format
> since the MIPI DBI spec doesn't have support for little endian.
> 
> drm_mipi_dbi is optimized for DBI interface option 3 which means that the
> 16-bit bytes are swapped by the upper layer if the SPI bus does not
> support 16 bits per word, signified by the swap_bytes member.
> 
> In order to support both 16-bit and 24-bit pixel transfers we need a way
> to tell the DBI command layer the format of the buffer. Add a
> write_memory_bpw member that the upper layer can use to tell how many
> bits per word to use for the SPI transfer.
> 
> v4:
> - Expand the commit message (Dmitry)
> 
> Signed-off-by: Noralf Tr?nnes <noralf@tronnes.org>
> ---
>  drivers/gpu/drm/drm_mipi_dbi.c | 14 ++++++++++----
>  include/drm/drm_mipi_dbi.h     |  5 +++++
>  2 files changed, 15 insertions(+), 4 deletions(-)
> 

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>


-- 
With best wishes
Dmitry