linux-kernel - [PATCH 4.4 25/31] drm/bridge: adv7511: Re-write the i2c address before EDID probing

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Date:   Tue, 12 Sep 2017 09:56:20 -0700
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>,
        Thong Ho <thong.ho.px@....renesas.com>,
        Nhan Nguyen <nhan.nguyen.yb@...esas.com>
Subject: [PATCH 4.4 25/31] drm/bridge: adv7511: Re-write the i2c address before EDID probing

4.4-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: Thong Ho <thong.ho.px@....renesas.com>
Signed-off-by: Nhan Nguyen <nhan.nguyen.yb@...esas.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/gpu/drm/i2c/adv7511.c |   11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

--- 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_
 				     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 devic
 	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;