linux-kernel - Re: [PATCH 5/7] usb: phy: tegra: get ULPI reset GPIO info using DT.

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Date:	Tue, 19 Mar 2013 14:03:55 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Venu Byravarasu <vbyravarasu@...dia.com>
CC:	gregkh@...uxfoundation.org, stern@...land.harvard.edu,
	balbi@...com, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-tegra@...r.kernel.org,
	devicetree-discuss@...ts.ozlabs.org
Subject: Re: [PATCH 5/7] usb: phy: tegra: get ULPI reset GPIO info using DT.

On 03/18/2013 06:29 AM, Venu Byravarasu wrote:
> As GPIO information is avail through DT, used it to get Tegra ULPI
> reset GPIO number. Added a new member to tegra_usb_phy structure to
> store this number.

> diff --git a/drivers/usb/phy/tegra_usb_phy.c b/drivers/usb/phy/tegra_usb_phy.c

> -	gpio_direction_output(config->reset_gpio, 0);
> +	gpio_direction_output(phy->reset_gpio, 0);
>  	msleep(5);
> -	gpio_direction_output(config->reset_gpio, 1);
> +	gpio_direction_output(phy->reset_gpio, 1);

That implies that the PHY reset signal is active-low. This should be
represented in the GPIO flags in the device tree. In other words,
instead of e.g.:

nvidia,phy-reset-gpio = <&gpio 169 0>; /* gpio PV1 */

you want:

nvidia,phy-reset-gpio = <&gpio 169 1>; /* gpio PV1 */

Flag 1 means active-low. See
Documentation/devicetree/bindings/gpio/nvidia,tegra20-gpio.txt. This is
a bug in the current device tree content, although it has no effect
since no code currently uses the GPIO flags from DT. I suggest creating
a separate patch to fix this, and inserting it between patch 1 and 2 of
the series.
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