[U-Boot] [PATCH] dm: i2c: mxc_i2c: implement i2c_idle_bus

[Simon Glass]

On 11 March 2016 at 01:47, Peng Fan <van.freenix at gmail.com> wrote:
> Implement i2c_idle_bus in driver, then setup_i2c can
> be dropped for boards which enable DM_I2C/DM_GPIO/PINCTRL.
> The i2c_idle_bus force bus idle flow follows setup_i2c in
> arch/arm/imx-common/i2c-mxv7.c
>
> This patch is an implementation following linux kernel patch:
> "
> commit 1c4b6c3bcf30d0804db0d0647d8ebeb862c6f7e5
> Author: Gao Pan <b54642 at freescale.com>
> Date:   Fri Oct 23 20:28:54 2015 +0800
>
>     i2c: imx: implement bus recovery
>
>     Implement bus recovery methods for i2c-imx so we can recover from
>     situations where SCL/SDA are stuck low.
>
>     Once i2c bus SCL/SDA are stuck low during transfer, config the i2c
>     pinctrl to gpio mode by calling pinctrl sleep set function, and then
>     use GPIO to emulate the i2c protocol to send nine dummy clock to recover
>     i2c device. After recovery, set i2c pinctrl to default group setting.
> "
>
> See Documentation/devicetree/bindings/i2c/i2c-imx.txt for detailed
> description.
> 1. Introuduce scl_gpio/sda_gpio/bus in mxc_i2c_bus.
> 2. Discard the __weak attribute for i2c_idle_bus and implement it,
>    since we have pinctrl driver/driver model gpio driver. We can
>    use device tree, but not let board code to do this.
> 3. gpio state for mxc_i2c is not a must, but it is recommended. If
>    there is no gpio state, driver will give tips, but not fail.
> 4. The i2c controller was first probed, default pinctrl state will
>    be used, so when need to use gpio function, need to do
>    "pinctrl_select_state(dev, "gpio")" and after force bus idle,
>    need to switch back "pinctrl_select_state(dev, "default")".
>
> This is example about how to use the gpio force bus
> idle function:
> "
>  &i2c1 {
>         clock-frequency = <100000>;
>         pinctrl-names = "default", "gpio";
>         pinctrl-0 = <&pinctrl_i2c1>;
>         pinctrl-1 = <&pinctrl_i2c1_gpio>;
>         scl-gpios = <&gpio1 28 GPIO_ACTIVE_HIGH>;
>         sda-gpios = <&gpio1 29 GPIO_ACTIVE_HIGH>;
>         status = "okay";
>         [....]
>  };
>
> [.....]
>
>         pinctrl_i2c1_gpio: i2c1grp_gpio {
>                 fsl,pins = <
>                         MX6UL_PAD_UART4_TX_DATA__GPIO1_IO28 0x1b8b0
>                         MX6UL_PAD_UART4_RX_DATA__GPIO1_IO29 0x1b8b0
>                 >;
>         };
> "
>
> Signed-off-by: Peng Fan <van.freenix at gmail.com>
> Cc: Albert Aribaud <albert.u.boot at aribaud.net>
> Cc: Stefano Babic <sbabic at denx.de>
> Cc: Heiko Schocher <hs at denx.de>
> Cc: Simon Glass <sjg at chromium.org>
> Cc: York Sun <york.sun at nxp.com>
> ---
>  arch/arm/include/asm/imx-common/mxc_i2c.h |  10 +++
>  drivers/i2c/mxc_i2c.c                     | 101 +++++++++++++++++++++++++++---
>  2 files changed, 102 insertions(+), 9 deletions(-)

Reviewed-by: Simon Glass <sjg at chromium.org>