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SubjectRe: [PATCH] i2c: mv64xxx: Add bus error recovery
Date
Hi Mark,

On 8/07/20 9:10 am, Mark Tomlinson wrote:
> This adds i2c bus recovery to the mv64xxx driver.
>
> Implement bus recovery to recover from SCL/SDA stuck low.
>
> This uses the generic recovery function, setting the clock/data lines as
> GPIO pins, and sending 9 clocks to try and recover the bus.
>
> Signed-off-by: Mark Tomlinson <mark.tomlinson@alliedtelesis.co.nz>

Reviewed-by: Chris Packham <chris.packham@alliedtelesis.co.nz>

One additional comment below

> ---
> drivers/i2c/busses/i2c-mv64xxx.c | 77 +++++++++++++++++++++++++++++++-
> 1 file changed, 76 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/i2c/busses/i2c-mv64xxx.c b/drivers/i2c/busses/i2c-mv64xxx.c
> index 829b8c98ae51..e58853ba3ef0 100644
> --- a/drivers/i2c/busses/i2c-mv64xxx.c
> +++ b/drivers/i2c/busses/i2c-mv64xxx.c
> @@ -21,6 +21,7 @@
> #include <linux/io.h>
> #include <linux/of.h>
> #include <linux/of_device.h>
> +#include <linux/of_gpio.h>
> #include <linux/of_irq.h>
> #include <linux/clk.h>
> #include <linux/err.h>
> @@ -147,6 +148,10 @@ struct mv64xxx_i2c_data {
> bool irq_clear_inverted;
> /* Clk div is 2 to the power n, not 2 to the power n + 1 */
> bool clk_n_base_0;
> + struct pinctrl *pinctrl;
> + struct i2c_bus_recovery_info rinfo;
> + struct pinctrl_state *pin_default_state;
> + struct pinctrl_state *pin_gpio_state;
> };
>
> static struct mv64xxx_i2c_regs mv64xxx_i2c_regs_mv64xxx = {
> @@ -325,7 +330,8 @@ mv64xxx_i2c_fsm(struct mv64xxx_i2c_data *drv_data, u32 status)
> drv_data->msg->flags);
> drv_data->action = MV64XXX_I2C_ACTION_SEND_STOP;
> mv64xxx_i2c_hw_init(drv_data);
> - drv_data->rc = -EIO;
> + i2c_recover_bus(&drv_data->adapter);
> + drv_data->rc = -EAGAIN;
> }
> }
>
> @@ -563,6 +569,7 @@ mv64xxx_i2c_wait_for_completion(struct mv64xxx_i2c_data *drv_data)
> "time_left: %d\n", drv_data->block,
> (int)time_left);
> mv64xxx_i2c_hw_init(drv_data);
> + i2c_recover_bus(&drv_data->adapter);
> }
> } else
> spin_unlock_irqrestore(&drv_data->lock, flags);
> @@ -872,6 +879,69 @@ mv64xxx_of_config(struct mv64xxx_i2c_data *drv_data,
> }
> #endif /* CONFIG_OF */
>
> +/*
> + * Switch to bit bang mode to prepare for i2c generic recovery.
> + */
> +static void mv64xxx_i2c_prepare_recovery(struct i2c_adapter *adap)
> +{
> + struct mv64xxx_i2c_data *drv_data = i2c_get_adapdata(adap);
> +
> + pinctrl_select_state(drv_data->pinctrl, drv_data->pin_gpio_state);
> +}
> +
> +/*
> + * Return to normal i2c operation following recovery.
> + */
> +static void mv64xxx_i2c_unprepare_recovery(struct i2c_adapter *adap)
> +{
> + struct mv64xxx_i2c_data *drv_data = i2c_get_adapdata(adap);
> +
> + pinctrl_select_state(drv_data->pinctrl, drv_data->pin_default_state);
> +}
> +
> +static int mv64xxx_i2c_init_recovery_info(struct mv64xxx_i2c_data *drv_data,
> + struct platform_device *pd)
> +{
> + struct i2c_bus_recovery_info *rinfo = &drv_data->rinfo;
> + struct device *dev = &pd->dev;
> +
> + drv_data->pinctrl = devm_pinctrl_get(dev);
> + if (!drv_data->pinctrl || IS_ERR(drv_data->pinctrl)) {
> + dev_err(dev, "can't get pinctrl, bus recovery not supported\n");
> + return PTR_ERR(drv_data->pinctrl);
> + }
> +
> + drv_data->pin_default_state = pinctrl_lookup_state(drv_data->pinctrl,
> + PINCTRL_STATE_DEFAULT);
> + drv_data->pin_gpio_state = pinctrl_lookup_state(drv_data->pinctrl,
> + "gpio");
> + rinfo->scl_gpiod = devm_gpiod_get(dev, "scl",
> + GPIOD_OUT_HIGH_OPEN_DRAIN);
> + rinfo->sda_gpiod = devm_gpiod_get(dev, "sda", GPIOD_IN);

Should these be mentioned in
Documentation/devicetree/bindings/i2c/marvell,mv64xxx-i2c.yaml?

> + if (PTR_ERR(rinfo->scl_gpiod) == -EPROBE_DEFER ||
> + PTR_ERR(rinfo->sda_gpiod) == -EPROBE_DEFER)
> + return -EPROBE_DEFER;
> +
> + if (IS_ERR(rinfo->sda_gpiod) ||
> + IS_ERR(rinfo->scl_gpiod) ||
> + IS_ERR(drv_data->pin_default_state) ||
> + IS_ERR(drv_data->pin_gpio_state)) {
> + dev_dbg(dev, "recovery information incomplete\n");
> + return 0;
> + }
> +
> + dev_dbg(dev, "using scl-gpio %d and sda-gpio %d for recovery\n",
> + rinfo->scl_gpiod ? desc_to_gpio(rinfo->scl_gpiod) : -1,
> + rinfo->sda_gpiod ? desc_to_gpio(rinfo->sda_gpiod) : -1);
> +
> + rinfo->prepare_recovery = mv64xxx_i2c_prepare_recovery;
> + rinfo->unprepare_recovery = mv64xxx_i2c_unprepare_recovery;
> + rinfo->recover_bus = i2c_generic_scl_recovery;
> + drv_data->adapter.bus_recovery_info = rinfo;
> +
> + return 0;
> +}
> +
> static int
> mv64xxx_i2c_probe(struct platform_device *pd)
> {
> @@ -939,6 +1009,10 @@ mv64xxx_i2c_probe(struct platform_device *pd)
>
> mv64xxx_i2c_hw_init(drv_data);
>
> + rc = mv64xxx_i2c_init_recovery_info(drv_data, pd);
> + if (rc == -EPROBE_DEFER)
> + goto exit_reset;
> +
> rc = request_irq(drv_data->irq, mv64xxx_i2c_intr, 0,
> MV64XXX_I2C_CTLR_NAME, drv_data);
> if (rc) {
> @@ -951,6 +1025,7 @@ mv64xxx_i2c_probe(struct platform_device *pd)
> "mv64xxx: Can't add i2c adapter, rc: %d\n", -rc);
> goto exit_free_irq;
> }
> + i2c_recover_bus(&drv_data->adapter);
>
> return 0;
>
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