linux-kernel - [PATCH AUTOSEL for 4.4 01/25] [media] adv7604: Initialize drive strength to default when using DT

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Message-ID: <20171025015607.24625-1-alexander.levin@verizon.com>
Date:   Wed, 25 Oct 2017 01:56:13 +0000
From:   "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Cc:     Lars-Peter Clausen <lars@...afoo.de>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Mauro Carvalho Chehab <mchehab@...pensource.com>,
        "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>
Subject: [PATCH AUTOSEL for 4.4 01/25] [media] adv7604: Initialize drive
 strength to default when using DT

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

[ Upstream commit da8892d410db224d9a24104529794e6e37e0c100 ]

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: Sasha Levin <alexander.levin@...izon.com>
---
 drivers/media/i2c/adv7604.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/media/i2c/adv7604.c b/drivers/media/i2c/adv7604.c
index 01adcdc52346..a9e2722f5e22 100644
--- a/drivers/media/i2c/adv7604.c
+++ b/drivers/media/i2c/adv7604.c
@@ -2856,6 +2856,9 @@ static int adv76xx_parse_dt(struct adv76xx_state *state)
 	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;
 }
-- 
2.11.0