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Sat, 28 Feb 2026 20:30:42 -0800 (PST) From: David Lechner Date: Sat, 28 Feb 2026 22:30:30 -0600 Subject: [PATCH] drm/sitronix/st7586: fix bad pixel data due to byte swap Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260228-drm-mipi-dbi-fix-st7586-byte-swap-v1-1-e78f6c24cd28@baylibre.com> X-B4-Tracking: v=1; b=H4sIAAAAAAAC/x2NzQqDMBAGX0X23A+2EW3wVUoPmmzaPaghK/1Bf HdDjwPDzE4mRcVoaHYq8lbTdalwvTQUXuPyFGisTI5dz855xDJj1qyIkyLpF7bdOt9j+m0C+4w ZiSO3oUueOVDt5CLV+z/uj+M4AVKtzG1zAAAA X-Change-ID: 20260228-drm-mipi-dbi-fix-st7586-byte-swap-f0d03c5f800c To: David Lechner , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , =?utf-8?q?Noralf_Tr=C3=B8nnes?= , Dmitry Baryshkov Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, David Lechner X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; 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This driver is for a monochrome display that has an unusual data format, so the default value set in mipi_dbi_spi_init() is not correct simply because this controller is non-standard. Previously, we were using dbi->swap_bytes to make the same sort of workaround, but it was removed in the same commit that added dbi->write_memory_bpw, so we need to use the latter now to have the correct behavior. This fixes every 3 columns of pixels being swapped on the display. There are 3 pixels per byte, so the byte swap caused this effect. Fixes: df3fb27a74a4 ("drm/mipi-dbi: Make bits per word configurable for pix= el transfers") Signed-off-by: David Lechner Acked-by: Thomas Zimmermann Reviewed-by: Javier Martinez Canillas --- drivers/gpu/drm/sitronix/st7586.c | 15 ++++++--------- 1 file changed, 6 insertions(+), 9 deletions(-) diff --git a/drivers/gpu/drm/sitronix/st7586.c b/drivers/gpu/drm/sitronix/s= t7586.c index b57ebf37a664..16b6b4e368af 100644 --- a/drivers/gpu/drm/sitronix/st7586.c +++ b/drivers/gpu/drm/sitronix/st7586.c @@ -347,6 +347,12 @@ static int st7586_probe(struct spi_device *spi) if (ret) return ret; =20 + /* + * Override value set by mipi_dbi_spi_init(). This driver is a bit + * non-standard, so best to set it explicitly here. + */ + dbi->write_memory_bpw =3D 8; + /* Cannot read from this controller via SPI */ dbi->read_commands =3D NULL; =20 @@ -356,15 +362,6 @@ static int st7586_probe(struct spi_device *spi) if (ret) return ret; =20 - /* - * we are using 8-bit data, so we are not actually swapping anything, - * but setting mipi->swap_bytes makes mipi_dbi_typec3_command() do the - * right thing and not use 16-bit transfers (which results in swapped - * bytes on little-endian systems and causes out of order data to be - * sent to the display). - */ - dbi->swap_bytes =3D true; - drm_mode_config_reset(drm); =20 ret =3D drm_dev_register(drm, 0); --- base-commit: 3fa5e5702a82d259897bd7e209469bc06368bf31 change-id: 20260228-drm-mipi-dbi-fix-st7586-byte-swap-f0d03c5f800c Best regards, --=20 David Lechner