linux-kernel - [PATCH 3.16 084/212] [media] adv7604: Initialize drive strength to default when using DT

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Date:   Thu, 01 Jun 2017 16:43:16 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Laurent Pinchart" <laurent.pinchart@...asonboard.com>,
        "Hans Verkuil" <hans.verkuil@...co.com>,
        "Niklas Söderlund" 
        <niklas.soderlund+renesas@...natech.se>,
        "Lars-Peter Clausen" <lars@...afoo.de>,
        "Mauro Carvalho Chehab" <mchehab@...pensource.com>
Subject: [PATCH 3.16 084/212] [media] adv7604: Initialize drive strength
 to default when using DT

3.16.44-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Lars-Peter Clausen <lars@...afoo.de>

commit da8892d410db224d9a24104529794e6e37e0c100 upstream.

The adv7604 driver platform data contains fields for configuring the drive
strength of the output pins. When probing the driver through DT these
fields are not explicitly initialized, which means they are left at 0. This
is a reserved setting for the drive strength configuration though and can
cause signal integrity issues.

Whether these signal integrity issues are visible depends on the PCB
specifics (e.g. the higher the load capacitance for the output the more
visible the issue). But it has been observed on existing solutions at high
pixel clock rates.

Initialize the drive strength settings to the power-on-reset value of the
device when probing through devicetree to avoid this issue.

Fixes: 0e158be0162b ("adv7604: Add DT support")

Signed-off-by: Lars-Peter Clausen <lars@...afoo.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Tested-by: Niklas Söderlund <niklas.soderlund+renesas@...natech.se>
Signed-off-by: Hans Verkuil <hans.verkuil@...co.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@...pensource.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/media/i2c/adv7604.c | 3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/media/i2c/adv7604.c
+++ b/drivers/media/i2c/adv7604.c
@@ -2735,6 +2735,9 @@ static int adv7604_parse_dt(struct adv76
 	state->pdata.alt_data_sat = 1;
 	state->pdata.op_format_mode_sel = ADV7604_OP_FORMAT_MODE0;
 	state->pdata.bus_order = ADV7604_BUS_ORDER_RGB;
+	state->pdata.dr_str_data = ADV76XX_DR_STR_MEDIUM_HIGH;
+	state->pdata.dr_str_clk = ADV76XX_DR_STR_MEDIUM_HIGH;
+	state->pdata.dr_str_sync = ADV76XX_DR_STR_MEDIUM_HIGH;

 	return 0;
 }