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Message-ID: <1444400578.28661.28.camel@hadess.net>
Subject: Re: [PATCH v8 2/9] Input: goodix - reset device at init
From: Bastien Nocera <hadess@hadess.net>
To: Irina Tirdea <irina.tirdea@intel.com>,
        Dmitry Torokhov <dmitry.torokhov@gmail.com>,
        Aleksei Mamlin <mamlinav@gmail.com>, Arnd Bergmann <arnd@arndb.de>,
        linux-input@vger.kernel.org
Cc: Mark Rutland <mark.rutland@arm.com>,
        Octavian Purdila <octavian.purdila@intel.com>,
        linux-kernel@vger.kernel.org, devicetree@vger.kernel.org
Date: Fri, 09 Oct 2015 16:22:58 +0200
In-Reply-To: <1444314231-19206-3-git-send-email-irina.tirdea@intel.com>
References: <1444314231-19206-1-git-send-email-irina.tirdea@intel.com>
	 <1444314231-19206-3-git-send-email-irina.tirdea@intel.com>
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On Thu, 2015-10-08 at 17:23 +0300, Irina Tirdea wrote:
> After power on, it is recommended that the driver resets the device.
> The reset procedure timing is described in the datasheet and is used
> at device init (before writing device configuration) and
> for power management. It is a sequence of setting the interrupt
> and reset pins high/low at specific timing intervals. This procedure
> also includes setting the slave address to the one specified in the
> ACPI/device tree.
> 
> This is based on Goodix datasheets for GT911 and GT9271 and on Goodix
> driver gt9xx.c for Android (publicly available in Android kernel
> trees for various devices).
> 
> For reset the driver needs to control the interrupt and
> reset gpio pins (configured through ACPI/device tree). For devices
> that do not have the gpio pins properly declared, the functionality
> depending on these pins will not be available, but the device can
> still
> be used with basic functionality.
> 
> For both device tree and ACPI, the interrupt gpio pin configuration
> is
> read from the "irq-gpio" property and the reset pin configuration is
> read from the "reset-gpio" property. For ACPI 5.1, named properties
> can be specified using the _DSD section. This functionality will not
> be
> available for devices that use indexed gpio pins declared in the _CRS
> section (we need to provide backward compatibility with devices
> that do not support using the interrupt gpio pin as output).
> 
> For ACPI, the pins can be specified using ACPI 5.1:
> Device (STAC)
> {
>     Name (_HID, "GDIX1001")
>     ...
> 
>     Method (_CRS, 0, Serialized)
>     {
>         Name (RBUF, ResourceTemplate ()
>         {
>             I2cSerialBus (0x0014, ControllerInitiated, 0x00061A80,
>                 AddressingMode7Bit, "\\I2C0",
>                 0x00, ResourceConsumer, ,
>                 )
> 
>             GpioInt (Edge, ActiveHigh, Exclusive, PullNone, 0x0000,
>                 "\\I2C0", 0x00, ResourceConsumer, ,
>                  )
>                  {   // Pin list
>                      0
>                  }
> 
>             GpioIo (Exclusive, PullDown, 0x0000, 0x0000,
>                 IoRestrictionOutputOnly, "\\I2C0", 0x00,
>                 ResourceConsumer, ,
>                 )
>                 {
>                      1
>                 }
>         })
>         Return (RBUF)
>     }
> 
>     Name (_DSD,  Package ()
>     {
>         ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
>         Package ()
>         {
>             Package (2) {"irq-gpio", Package() {^STAC, 0, 0, 0 }},
>             Package (2) {"reset-gpio", Package() {^STAC, 1, 0, 0 }},
>             ...
>         }
>     }
> 
> Signed-off-by: Octavian Purdila <octavian.purdila@intel.com>
> Signed-off-by: Irina Tirdea <irina.tirdea@intel.com>

Didn't actually cause problems on my system, and the documentation
looks good.

Acked-by: Bastien Nocera <hadess@hadess.net>