linux-arm-kernel.lists.infradead.org archive mirror
 help / color / mirror / Atom feed
* [PATCH] drm: i2c: tda998x: Retry fetching the EDID if it fails first time.
@ 2014-11-18 17:41 Andrew Jackson
  2014-11-28  8:19 ` Jean-Francois Moine
  0 siblings, 1 reply; 5+ messages in thread
From: Andrew Jackson @ 2014-11-18 17:41 UTC (permalink / raw)
  To: linux-arm-kernel

Fetching the EDID from a connected monitor is an automated thing
with NXP TDA19988. But on some boards the fetching fails for the
first time silently without any indication that an error has occured.
More than that, subsequent fetches of the EDID succeed until the
monitor(s) are unplugged.

Add a function to validate the read EDID and retry if the block
retrieved is not valid.

Signed-off-by: Andrew Jackson <Andrew.Jackson@arm.com>
Signed-off-by: Liviu Dudau <Liviu.Dudau@arm.com>
---
 drivers/gpu/drm/i2c/tda998x_drv.c |   36 ++++++++++++++++++++++++++++--------
 1 files changed, 28 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/i2c/tda998x_drv.c b/drivers/gpu/drm/i2c/tda998x_drv.c
index d476279..025adc0 100644
--- a/drivers/gpu/drm/i2c/tda998x_drv.c
+++ b/drivers/gpu/drm/i2c/tda998x_drv.c
@@ -1066,11 +1066,36 @@ static int read_edid_block(struct tda998x_priv *priv, uint8_t *buf, int blk)
 	return 0;
 }
 
+static int
+read_validate_edid_block(struct tda998x_priv *priv, uint8_t *buf, int blk)
+{
+	bool print_bad_edid = drm_debug & DRM_UT_KMS;
+	int ret;
+	int retries = 1;
+
+	do
+	{
+		bool print_bad = print_bad_edid && (retries == 0);
+
+		ret = read_edid_block(priv, buf, blk);
+		/* Fail on I2C error */
+		if (ret)
+			break;
+
+		/* But retry checksum errored blocks */
+		if (drm_edid_block_valid(buf, blk, print_bad))
+			break;
+		else
+			ret = -EINVAL;
+	} while (retries-- > 0);
+
+	return ret;
+}
+
 static uint8_t *do_get_edid(struct tda998x_priv *priv)
 {
 	int j, valid_extensions = 0;
 	uint8_t *block, *new;
-	bool print_bad_edid = drm_debug & DRM_UT_KMS;
 
 	if ((block = kmalloc(EDID_LENGTH, GFP_KERNEL)) == NULL)
 		return NULL;
@@ -1079,10 +1104,7 @@ static uint8_t *do_get_edid(struct tda998x_priv *priv)
 		reg_clear(priv, REG_TX4, TX4_PD_RAM);
 
 	/* base block fetch */
-	if (read_edid_block(priv, block, 0))
-		goto fail;
-
-	if (!drm_edid_block_valid(block, 0, print_bad_edid))
+	if (read_validate_edid_block(priv, block, 0))
 		goto fail;
 
 	/* if there's no extensions, we're done */
@@ -1096,10 +1118,8 @@ static uint8_t *do_get_edid(struct tda998x_priv *priv)
 
 	for (j = 1; j <= block[0x7e]; j++) {
 		uint8_t *ext_block = block + (valid_extensions + 1) * EDID_LENGTH;
-		if (read_edid_block(priv, ext_block, j))
-			goto fail;
 
-		if (!drm_edid_block_valid(ext_block, j, print_bad_edid))
+		if (read_validate_edid_block(priv, ext_block, j))
 			goto fail;
 
 		valid_extensions++;
-- 
1.7.1

^ permalink raw reply related	[flat|nested] 5+ messages in thread
end of thread, other threads:[~2014-12-01 13:19 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2014-11-18 17:41 [PATCH] drm: i2c: tda998x: Retry fetching the EDID if it fails first time Andrew Jackson
2014-11-28  8:19 ` Jean-Francois Moine
2014-11-28  9:02   ` Andrew Jackson
2014-11-29 10:41     ` Jean-Francois Moine
2014-12-01 13:19       ` Andrew Jackson

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).