[PATCH 4.4.y] drm: adv7511: Re-write the i2c address before EDID probing

[Nhan Nguyen]

commit 3587c856675c45809010c2cee5b21096f6e8e938 upstream.

I've found that by just turning the chip on and off via the
POWER_DOWN register, I end up getting i2c_transfer errors on
HiKey.

Investigating further, it turns out that some of the register
state in hardware is getting lost, as the device registers are
reset when the chip is powered down.

Thus this patch simply re-writes the i2c address to the
ADV7511_REG_EDID_I2C_ADDR register to ensure its properly set
before we try to read the EDID data.

Cc: David Airlie <airlied at linux.ie>
Cc: Archit Taneja <architt at codeaurora.org>
Cc: Wolfram Sang <wsa+renesas at sang-engineering.com>
Cc: Lars-Peter Clausen <lars at metafoo.de>
Cc: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
Cc: dri-devel at lists.freedesktop.org
Cc: stable at vger.kernel.org
Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
Tested-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
Signed-off-by: John Stultz <john.stultz at linaro.org>
Signed-off-by: Archit Taneja <architt at codeaurora.org>
Signed-off-by: Thong Ho <thong.ho.px at rvc.renesas.com>
Signed-off-by: Nhan Nguyen <nhan.nguyen.yb at renesas.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1484614372-15342-7-git-send-email-john.stultz@linaro.org
---
 drivers/gpu/drm/i2c/adv7511.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i2c/adv7511.c b/drivers/gpu/drm/i2c/adv7511.c
index ebb0fc8..dba5c0e 100644
--- a/drivers/gpu/drm/i2c/adv7511.c
+++ b/drivers/gpu/drm/i2c/adv7511.c
@@ -51,6 +51,10 @@ struct adv7511 {
 	struct gpio_desc *gpio_pd;
 };
 
+static const int edid_i2c_addr = 0x7e;
+static const int packet_i2c_addr = 0x70;
+static const int cec_i2c_addr = 0x78;
+
 static struct adv7511 *encoder_to_adv7511(struct drm_encoder *encoder)
 {
 	return to_encoder_slave(encoder)->slave_priv;
@@ -606,6 +610,9 @@ static int adv7511_get_modes(struct drm_encoder *encoder,
 				     ADV7511_INT1_DDC_ERROR);
 		}
 		adv7511->current_edid_segment = -1;
+		/* Reset the EDID_I2C_ADDR register as it might be cleared */
+		regmap_write(adv7511->regmap, ADV7511_REG_EDID_I2C_ADDR,
+				edid_i2c_addr);
 	}
 
 	edid = drm_do_get_edid(connector, adv7511_get_edid_block, adv7511);
@@ -881,10 +888,6 @@ static int adv7511_parse_dt(struct device_node *np,
 	return 0;
 }
 
-static const int edid_i2c_addr = 0x7e;
-static const int packet_i2c_addr = 0x70;
-static const int cec_i2c_addr = 0x78;
-
 static int adv7511_probe(struct i2c_client *i2c, const struct i2c_device_id *id)
 {
 	struct adv7511_link_config link_config;
-- 
1.9.1