linux-kernel - [PATCH v2 12/15] ARM: dts: dra71-evm: Select pull down for mmc1

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Message-ID: <20180206125806.19350-13-kishon@ti.com>
Date:   Tue, 6 Feb 2018 18:28:03 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     Benoît Cousson <bcousson@...libre.com>,
        Tony Lindgren <tony@...mide.com>,
        Rob Herring <robh+dt@...nel.org>
CC:     Mark Rutland <mark.rutland@....com>,
        Russell King <linux@...linux.org.uk>,
        <linux-omap@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        Kishon Vijay Abraham I <kishon@...com>
Subject: [PATCH v2 12/15] ARM: dts: dra71-evm: Select pull down for mmc1_clk line in default mode

During a short period when the bus voltage is switched from 3.3v to 1.8v,
(to enumerate UHS mode), the mmc module is disabled and the mmc IO lines
are kept in a state according to the programmed pad mux pull type.

According to 4.2.4.2 Timing to Switch Signal Voltage in "SD Specifications
Part 1 Physical Layer Specification Version 5.00 February 22, 2016", the
host should hold CLK low for at least 5ms.

In order to keep the card line low during voltage switch, the pad mux of
mmc1_clk line should be configured to pull down.

This is specific only to dra71-evm (and not all dra72 based boards) since
mmc1_clk line in dra71-evm is not connected to an external pullup.

Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
---
 arch/arm/boot/dts/dra71-evm.dts | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/arch/arm/boot/dts/dra71-evm.dts b/arch/arm/boot/dts/dra71-evm.dts
index 64363f75c01a..ebc4bbae981e 100644
--- a/arch/arm/boot/dts/dra71-evm.dts
+++ b/arch/arm/boot/dts/dra71-evm.dts
@@ -50,6 +50,19 @@
 	};
 };
 
+&dra7_pmx_core {
+	mmc1_pins_default: mmc1_pins_default {
+		pinctrl-single,pins = <
+			DRA7XX_CORE_IOPAD(0x3754, PIN_INPUT_PULLDOWN | MUX_MODE0) /* mmc1_clk.clk */
+			DRA7XX_CORE_IOPAD(0x3758, PIN_INPUT_PULLUP | MUX_MODE0) /* mmc1_cmd.cmd */
+			DRA7XX_CORE_IOPAD(0x375c, PIN_INPUT_PULLUP | MUX_MODE0) /* mmc1_dat0.dat0 */
+			DRA7XX_CORE_IOPAD(0x3760, PIN_INPUT_PULLUP | MUX_MODE0) /* mmc1_dat1.dat1 */
+			DRA7XX_CORE_IOPAD(0x3764, PIN_INPUT_PULLUP | MUX_MODE0) /* mmc1_dat2.dat2 */
+			DRA7XX_CORE_IOPAD(0x3768, PIN_INPUT_PULLUP | MUX_MODE0) /* mmc1_dat3.dat3 */
+		>;
+	};
+};
+
 &i2c1 {
 	status = "okay";
 	clock-frequency = <400000>;
-- 
2.11.0