Re: [PATCH v3 2/6] i2c: at91: implement i2c bus recovery

Ludovic Desroches
2020-01-27T08:51:20Z

On Wed, Jan 15, 2020 at 01:54:18PM +0200, Codrin Ciubotariu wrote:
> From: Kamel Bouhara <kamel.bouhara@bootlin.com>
>
> Implement i2c bus recovery when slaves devices might hold SDA low.
> In this case re-assign SCL/SDA to gpios and issue 9 dummy clock pulses
> until the slave release SDA.
>
> Signed-off-by: Kamel Bouhara <kamel.bouhara@bootlin.com>
> Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@microchip.com>
Acked-by: Ludovic Desroches <ludovic.desroches@microchip.com>

> ---
>
> Changes in v3:
> - removed unnecessary condition from info print;
> - removed unneded declarations;
>
> Changes in v2:
> - called i2c_recover_bus() after an error occurs, if SDA is down;
> - release gpios if recovery information is incomplete;
>
> drivers/i2c/busses/i2c-at91-master.c | 78 ++++++++++++++++++++++++++++
> drivers/i2c/busses/i2c-at91.h | 4 ++
> 2 files changed, 82 insertions(+)
>
> diff --git a/drivers/i2c/busses/i2c-at91-master.c b/drivers/i2c/busses/i2c-at91-master.c
> index 7a862e00b475..0aba51a7df32 100644
> --- a/drivers/i2c/busses/i2c-at91-master.c
> +++ b/drivers/i2c/busses/i2c-at91-master.c
> @@ -18,11 +18,13 @@
> #include <linux/dma-mapping.h>
> #include <linux/dmaengine.h>
> #include <linux/err.h>
> +#include <linux/gpio/consumer.h>
> #include <linux/i2c.h>
> #include <linux/interrupt.h>
> #include <linux/io.h>
> #include <linux/of.h>
> #include <linux/of_device.h>
> +#include <linux/pinctrl/consumer.h>
> #include <linux/platform_device.h>
> #include <linux/platform_data/dma-atmel.h>
> #include <linux/pm_runtime.h>
> @@ -478,6 +480,7 @@ static int at91_do_twi_transfer(struct at91_twi_dev *dev)
> unsigned long time_left;
> bool has_unre_flag = dev->pdata->has_unre_flag;
> bool has_alt_cmd = dev->pdata->has_alt_cmd;
> + struct i2c_bus_recovery_info *rinfo = &dev->rinfo;
>
> /*
> * WARNING: the TXCOMP bit in the Status Register is NOT a clear on
> @@ -637,6 +640,13 @@ static int at91_do_twi_transfer(struct at91_twi_dev *dev)
> at91_twi_write(dev, AT91_TWI_CR,
> AT91_TWI_THRCLR | AT91_TWI_LOCKCLR);
> }
> +
> + if (rinfo->get_sda && !(rinfo->get_sda(&dev->adapter))) {
> + dev_dbg(dev->dev,
> + "SDA is down; clear bus using gpio\n");
> + i2c_recover_bus(&dev->adapter);
> + }
> +
> return ret;
> }
>
> @@ -806,6 +816,70 @@ static int at91_twi_configure_dma(struct at91_twi_dev *dev, u32 phy_addr)
> return ret;
> }
>
> +static void at91_prepare_twi_recovery(struct i2c_adapter *adap)
> +{
> + struct at91_twi_dev *dev = i2c_get_adapdata(adap);
> +
> + pinctrl_select_state(dev->pinctrl, dev->pinctrl_pins_gpio);
> +}
> +
> +static void at91_unprepare_twi_recovery(struct i2c_adapter *adap)
> +{
> + struct at91_twi_dev *dev = i2c_get_adapdata(adap);
> +
> + pinctrl_select_state(dev->pinctrl, dev->pinctrl_pins_default);
> +}
> +
> +static int at91_init_twi_recovery_info(struct platform_device *pdev,
> + struct at91_twi_dev *dev)
> +{
> + struct i2c_bus_recovery_info *rinfo = &dev->rinfo;
> +
> + dev->pinctrl = devm_pinctrl_get(&pdev->dev);
> + if (!dev->pinctrl || IS_ERR(dev->pinctrl)) {
> + dev_info(dev->dev, "can't get pinctrl, bus recovery not supported\n");
> + return PTR_ERR(dev->pinctrl);
> + }
> +
> + dev->pinctrl_pins_default = pinctrl_lookup_state(dev->pinctrl,
> + PINCTRL_STATE_DEFAULT);
> + dev->pinctrl_pins_gpio = pinctrl_lookup_state(dev->pinctrl,
> + "gpio");
> + rinfo->sda_gpiod = devm_gpiod_get(&pdev->dev, "sda", GPIOD_IN);
> + if (PTR_ERR(rinfo->sda_gpiod) == -EPROBE_DEFER)
> + return -EPROBE_DEFER;
> +
> + rinfo->scl_gpiod = devm_gpiod_get(&pdev->dev, "scl",
> + GPIOD_OUT_HIGH_OPEN_DRAIN);
> + if (PTR_ERR(rinfo->scl_gpiod) == -EPROBE_DEFER)
> + return -EPROBE_DEFER;
> +
> + if (IS_ERR(rinfo->sda_gpiod) ||
> + IS_ERR(rinfo->scl_gpiod) ||
> + IS_ERR(dev->pinctrl_pins_default) ||
> + IS_ERR(dev->pinctrl_pins_gpio)) {
> + dev_info(&pdev->dev, "recovery information incomplete\n");
> + if (!IS_ERR(rinfo->sda_gpiod)) {
> + gpiod_put(rinfo->sda_gpiod);
> + rinfo->sda_gpiod = NULL;
> + }
> + if (!IS_ERR(rinfo->scl_gpiod)) {
> + gpiod_put(rinfo->scl_gpiod);
> + rinfo->scl_gpiod = NULL;
> + }
> + return -EINVAL;
> + }
> +
> + dev_info(&pdev->dev, "using scl, sda for recovery\n");
> +
> + rinfo->prepare_recovery = at91_prepare_twi_recovery;
> + rinfo->unprepare_recovery = at91_unprepare_twi_recovery;
> + rinfo->recover_bus = i2c_generic_scl_recovery;
> + dev->adapter.bus_recovery_info = rinfo;
> +
> + return 0;
> +}
> +
> int at91_twi_probe_master(struct platform_device *pdev,
> u32 phy_addr, struct at91_twi_dev *dev)
> {
> @@ -838,6 +912,10 @@ int at91_twi_probe_master(struct platform_device *pdev,
> "i2c-analog-filter");
> at91_calc_twi_clock(dev);
>
> + rc = at91_init_twi_recovery_info(pdev, dev);
> + if (rc == -EPROBE_DEFER)
> + return rc;
> +
> dev->adapter.algo = &at91_twi_algorithm;
> dev->adapter.quirks = &at91_twi_quirks;
>
> diff --git a/drivers/i2c/busses/i2c-at91.h b/drivers/i2c/busses/i2c-at91.h
> index 977a67bc0f88..f57a6cab96b4 100644
> --- a/drivers/i2c/busses/i2c-at91.h
> +++ b/drivers/i2c/busses/i2c-at91.h
> @@ -151,6 +151,10 @@ struct at91_twi_dev {
> u32 fifo_size;
> struct at91_twi_dma dma;
> bool slave_detected;
> + struct i2c_bus_recovery_info rinfo;
> + struct pinctrl *pinctrl;
> + struct pinctrl_state *pinctrl_pins_default;
> + struct pinctrl_state *pinctrl_pins_gpio;
> #ifdef CONFIG_I2C_AT91_SLAVE_EXPERIMENTAL
> unsigned smr;
> struct i2c_client *slave;
> --
> 2.20.1
>