From: Paul Cercueil paul@crapouillou.net
commit 900ab59e2621053b009f707f80b2c19ce0af5dee upstream.
The function mipi_dbi_spi1_transfer() will transfer its payload as 9-bit data, the 9th (MSB) bit being the data/command bit. In order to do that, it unpacks the 8-bit values into 16-bit values, then sets the 9th bit if the byte corresponds to data, clears it otherwise. The 7 MSB are padding. The array of now 16-bit values is then passed to the SPI core for transfer.
This function was broken since its introduction, as the length of the SPI transfer was set to the payload size before its conversion, but the payload doubled in size due to the 8-bit -> 16-bit conversion.
Fixes: 02dd95fe3169 ("drm/tinydrm: Add MIPI DBI support") Cc: stable@vger.kernel.org # 5.4+ Signed-off-by: Paul Cercueil paul@crapouillou.net Reviewed-by: Sam Ravnborg sam@ravnborg.org Reviewed-by: Noralf Trønnes noralf@tronnes.org Signed-off-by: Sam Ravnborg sam@ravnborg.org Link: https://patchwork.freedesktop.org/patch/msgid/20200703141341.1266263-1-paul@... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/gpu/drm/drm_mipi_dbi.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/gpu/drm/drm_mipi_dbi.c +++ b/drivers/gpu/drm/drm_mipi_dbi.c @@ -937,7 +937,7 @@ static int mipi_dbi_spi1_transfer(struct } }
- tr.len = chunk; + tr.len = chunk * 2; len -= chunk;
ret = spi_sync(spi, &m);