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[3/5] drm/panel: s6e63m0: Add some explanations

Message ID 20201110234653.2248594-4-linus.walleij@linaro.org (mailing list archive)
State New, archived
Headers show
Series Samsung s6e63m0 improvements | expand

Commit Message

Linus Walleij Nov. 10, 2020, 11:46 p.m. UTC 
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 <stephan@gerhold.net>
Cc: Paweł Chmiel <pawel.mikolaj.chmiel@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
 drivers/gpu/drm/panel/panel-samsung-s6e63m0-spi.c | 7 +++++++
 1 file changed, 7 insertions(+)
diff mbox series

Patch

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);
 	}