linux-kernel - [PATCH 4.9 81/87] drm/bridge: adv7511: Re-write the i2c address before EDID probing

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Date:   Mon, 13 Nov 2017 13:56:38 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, David Airlie <airlied@...ux.ie>,
        Archit Taneja <architt@...eaurora.org>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        dri-devel@...ts.freedesktop.org,
        John Stultz <john.stultz@...aro.org>,
        Nhan Nguyen <nhan.nguyen.yb@...esas.com>
Subject: [PATCH 4.9 81/87] drm/bridge: adv7511: Re-write the i2c address before EDID probing

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: John Stultz <john.stultz@...aro.org>

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@...ux.ie>
Cc: Archit Taneja <architt@...eaurora.org>
Cc: Wolfram Sang <wsa+renesas@...g-engineering.com>
Cc: Lars-Peter Clausen <lars@...afoo.de>
Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: dri-devel@...ts.freedesktop.org
Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Tested-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Signed-off-by: John Stultz <john.stultz@...aro.org>
Signed-off-by: Archit Taneja <architt@...eaurora.org>
Link: http://patchwork.freedesktop.org/patch/msgid/1484614372-15342-7-git-send-email-john.stultz@linaro.org
Signed-off-by: Nhan Nguyen <nhan.nguyen.yb@...esas.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/gpu/drm/bridge/adv7511/adv7511_drv.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
+++ b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
@@ -573,9 +573,17 @@ static int adv7511_get_modes(struct adv7
 	unsigned int count;
 
 	/* Reading the EDID only works if the device is powered */
-	if (!adv7511->powered)
+	if (!adv7511->powered) {
+		unsigned int edid_i2c_addr =
+					(adv7511->i2c_main->addr << 1) + 4;
+
 		__adv7511_power_on(adv7511);
 
+		/* 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);
 
 	if (!adv7511->powered)