On Thu, Apr 14, 2016 at 10:04:56PM +0800, Jisheng Zhang wrote:
> Implement bus recovery methods for i2c designware so we can recover
> from situations where SCL/SDA are stuck low.
> 
> The recovery method is similar as i2c-imx: "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.
> 
> Signed-off-by: Jisheng Zhang <jszh...@marvell.com>
> ---
> depends on runtime pm patches
> http://lists.infradead.org/pipermail/linux-arm-kernel/2016-April/422202.html
>  .../devicetree/bindings/i2c/i2c-designware.txt     | 12 ++++++
>  drivers/i2c/busses/i2c-designware-core.c           |  6 ++-
>  drivers/i2c/busses/i2c-designware-core.h           |  4 ++
>  drivers/i2c/busses/i2c-designware-platdrv.c        | 50 
> ++++++++++++++++++++++
>  4 files changed, 71 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/devicetree/bindings/i2c/i2c-designware.txt 
> b/Documentation/devicetree/bindings/i2c/i2c-designware.txt
> index fee26dc..51a55c6 100644
> --- a/Documentation/devicetree/bindings/i2c/i2c-designware.txt
> +++ b/Documentation/devicetree/bindings/i2c/i2c-designware.txt
> @@ -20,6 +20,13 @@ Optional properties :
>   - i2c-sda-falling-time-ns : should contain the SDA falling time in 
> nanoseconds.
>     This value which is by default 300ns is used to compute the tHIGH period.
>  
> + - scl-gpios: specify the gpio related to SCL pin
> +
> + - sda-gpios: specify the gpio related to SDA pin
> +
> + - pinctrl: add extra pinctrl to configure i2c pins to gpio function for i2c
> +   bus recovery, call it "gpio" state
> +
>  Example :
>  
>       i2c@f0000 {
> @@ -42,4 +49,9 @@ Example :
>               i2c-sda-hold-time-ns = <300>;
>               i2c-sda-falling-time-ns = <300>;
>               i2c-scl-falling-time-ns = <300>;
> +             pinctrl-names = "default", "gpio";
> +             pinctrl-0 = <&pinctrl_i2c1_default>;
> +             pinctrl-1 = <&pinctrl_i2c1_gpio>;
> +             scl-gpios = <&porta 26 GPIO_ACTIVE_HIGH>;
> +             sda-gpios = <&porta 27 GPIO_ACTIVE_HIGH>;
>       };
> diff --git a/drivers/i2c/busses/i2c-designware-core.c 
> b/drivers/i2c/busses/i2c-designware-core.c
> index 4255eaa..be40de1 100644
> --- a/drivers/i2c/busses/i2c-designware-core.c
> +++ b/drivers/i2c/busses/i2c-designware-core.c
> @@ -399,7 +399,10 @@ static int i2c_dw_wait_bus_not_busy(struct dw_i2c_dev 
> *dev)
>       while (dw_readl(dev, DW_IC_STATUS) & DW_IC_STATUS_ACTIVITY) {
>               if (timeout <= 0) {
>                       dev_warn(dev->dev, "timeout waiting for bus ready\n");
> -                     return -ETIMEDOUT;
> +                     i2c_recover_bus(&dev->adapter);
> +                     if (dw_readl(dev, DW_IC_STATUS)
> +                                     & DW_IC_STATUS_ACTIVITY)
> +                             return -ETIMEDOUT;
>               }
>               timeout--;
>               usleep_range(1000, 1100);
> @@ -665,6 +668,7 @@ i2c_dw_xfer(struct i2c_adapter *adap, struct i2c_msg 
> msgs[], int num)
>       /* wait for tx to complete */
>       if (!wait_for_completion_timeout(&dev->cmd_complete, HZ)) {
>               dev_err(dev->dev, "controller timed out\n");
> +             i2c_recover_bus(&dev->adapter);
>               /* i2c_dw_init implicitly disables the adapter */
>               i2c_dw_init(dev);
>               ret = -ETIMEDOUT;
> diff --git a/drivers/i2c/busses/i2c-designware-core.h 
> b/drivers/i2c/busses/i2c-designware-core.h
> index cd409e7..26c84ee 100644
> --- a/drivers/i2c/busses/i2c-designware-core.h
> +++ b/drivers/i2c/busses/i2c-designware-core.h
> @@ -104,6 +104,10 @@ struct dw_i2c_dev {
>       u16                     fs_lcnt;
>       int                     (*acquire_lock)(struct dw_i2c_dev *dev);
>       void                    (*release_lock)(struct dw_i2c_dev *dev);
> +     struct i2c_bus_recovery_info rinfo;
> +     struct pinctrl          *pinctrl;
> +     struct pinctrl_state    *pinctrl_pins_default;
> +     struct pinctrl_state    *pinctrl_pins_gpio;
>       bool                    pm_runtime_disabled;
>  };
>  
> diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c 
> b/drivers/i2c/busses/i2c-designware-platdrv.c
> index 1488cea..62bded9 100644
> --- a/drivers/i2c/busses/i2c-designware-platdrv.c
> +++ b/drivers/i2c/busses/i2c-designware-platdrv.c
> @@ -33,6 +33,7 @@
>  #include <linux/err.h>
>  #include <linux/interrupt.h>
>  #include <linux/of.h>
> +#include <linux/of_gpio.h>
>  #include <linux/platform_device.h>
>  #include <linux/pm.h>
>  #include <linux/pm_runtime.h>
> @@ -148,6 +149,49 @@ static int i2c_dw_plat_prepare_clk(struct dw_i2c_dev 
> *i_dev, bool prepare)
>       return 0;
>  }
>  
> +static void i2c_dw_plat_prepare_recovery(struct i2c_adapter *adap)
> +{
> +     struct dw_i2c_dev *dev = i2c_get_adapdata(adap);
> +
> +     pinctrl_select_state(dev->pinctrl, dev->pinctrl_pins_gpio);
> +}
> +
> +static void i2c_dw_plat_unprepare_recovery(struct i2c_adapter *adap)
> +{
> +     struct dw_i2c_dev *dev = i2c_get_adapdata(adap);
> +
> +     pinctrl_select_state(dev->pinctrl, dev->pinctrl_pins_default);
> +}
> +
> +static void i2c_dw_plat_init_recovery_info(struct dw_i2c_dev *dev,
> +                                        struct platform_device *pdev)
> +{
> +     struct i2c_bus_recovery_info *rinfo = &dev->rinfo;
> +
> +     dev->pinctrl_pins_default = pinctrl_lookup_state(dev->pinctrl,
> +                     PINCTRL_STATE_DEFAULT);
> +     dev->pinctrl_pins_gpio = pinctrl_lookup_state(dev->pinctrl,
> +                     "gpio");
> +     rinfo->sda_gpio = of_get_named_gpio(pdev->dev.of_node, "sda-gpios", 0);
> +     rinfo->scl_gpio = of_get_named_gpio(pdev->dev.of_node, "scl-gpios", 0);
> +
> +     if (!gpio_is_valid(rinfo->sda_gpio) ||
> +         !gpio_is_valid(rinfo->scl_gpio) ||
> +         IS_ERR(dev->pinctrl_pins_default) ||
> +         IS_ERR(dev->pinctrl_pins_gpio)) {
> +             dev_dbg(&pdev->dev, "recovery information incomplete\n");
> +             return;
> +     }
> +
> +     dev_dbg(&pdev->dev, "using scl-gpio %d and sda-gpio %d for recovery\n",
> +             rinfo->sda_gpio, rinfo->scl_gpio);
> +
> +     rinfo->prepare_recovery = i2c_dw_plat_prepare_recovery;
> +     rinfo->unprepare_recovery = i2c_dw_plat_unprepare_recovery;
> +     rinfo->recover_bus = i2c_generic_gpio_recovery;

This whole thing is DT specific and I don't see how we can do the same
for ACPI. Should it be enabled only when the controller was enumerated
from DT?

> +     dev->adapter.bus_recovery_info = rinfo;
> +}
> +
>  static int dw_i2c_plat_probe(struct platform_device *pdev)
>  {
>       struct dw_i2c_platform_data *pdata = dev_get_platdata(&pdev->dev);
> @@ -165,6 +209,12 @@ static int dw_i2c_plat_probe(struct platform_device 
> *pdev)
>       if (!dev)
>               return -ENOMEM;
>  
> +     dev->pinctrl = devm_pinctrl_get(&pdev->dev);
> +     if (IS_ERR(dev->pinctrl))
> +             return PTR_ERR(dev->pinctrl);
> +
> +     i2c_dw_plat_init_recovery_info(dev, pdev);
> +
>       mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>       dev->base = devm_ioremap_resource(&pdev->dev, mem);
>       if (IS_ERR(dev->base))
> -- 
> 2.8.0.rc3

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