The SPI DCS code was a bit hard to understand as the
device accepts 9-bit transfers packed into 16-bit words
with the most significant bit in bit 9 of the
16-bit word. Add some clarifying comments.
Cc: Stephan Gerhold <step...@gerhold.net>
Cc: Paweł Chmiel <pawel.mikolaj.chm...@gmail.com>
Signed-off-by: Linus Walleij <linus.wall...@linaro.org>
---
drivers/gpu/drm/panel/panel-samsung-s6e63m0-spi.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/drivers/gpu/drm/panel/panel-samsung-s6e63m0-spi.c
b/drivers/gpu/drm/panel/panel-samsung-s6e63m0-spi.c
index 9e1552a7ccc7..e47647f418ff 100644
--- a/drivers/gpu/drm/panel/panel-samsung-s6e63m0-spi.c
+++ b/drivers/gpu/drm/panel/panel-samsung-s6e63m0-spi.c
@@ -42,10 +42,17 @@ static int s6e63m0_spi_dcs_write(struct device *dev, const
u8 *data, size_t len)
int ret = 0;
dev_dbg(dev, "SPI writing dcs seq: %*ph\n", (int)len, data);
+
+ /*
+ * This sends 9 bits with the first bit (bit 8) set to 0
+ * This indicates that this is a command. Anything after the
+ * command is data.
+ */
ret = s6e63m0_spi_write_word(dev, *data);
while (!ret && --len) {
++data;
+ /* This sends 9 bits with the first bit (bit 8) set to 1 */
ret = s6e63m0_spi_write_word(dev, *data | DATA_MASK);
}
--
2.26.2
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