From 900ab59e2621053b009f707f80b2c19ce0af5dee Mon Sep 17 00:00:00 2001 From: Paul Cercueil Date: Fri, 3 Jul 2020 16:13:41 +0200 Subject: [PATCH] drm/dbi: Fix SPI Type 1 (9-bit) transfer MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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: # 5.4+ Signed-off-by: Paul Cercueil Reviewed-by: Sam Ravnborg Reviewed-by: Noralf Trønnes Signed-off-by: Sam Ravnborg Link: https://patchwork.freedesktop.org/patch/msgid/20200703141341.1266263-1-paul@crapouillou.net --- drivers/gpu/drm/drm_mipi_dbi.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpu/drm/drm_mipi_dbi.c b/drivers/gpu/drm/drm_mipi_dbi.c index bb27c82..bf7888a 100644 --- a/drivers/gpu/drm/drm_mipi_dbi.c +++ b/drivers/gpu/drm/drm_mipi_dbi.c @@ -923,7 +923,7 @@ static int mipi_dbi_spi1_transfer(struct mipi_dbi *dbi, int dc, } } - tr.len = chunk; + tr.len = chunk * 2; len -= chunk; ret = spi_sync(spi, &m); -- 2.7.4