From: Viresh Kumar <viresh.kumar@xxxxxx> Add i2c bus recovery infrastructure to i2c adapters as specified in the i2c protocol Rev. 03 section 3.1.16 titled "Bus clear". http://www.nxp.com/documents/user_manual/UM10204.pdf Sometimes during operation i2c bus hangs and we need to give dummy clocks to slave device to start the transfer again. Now we may have capability in the bus controller to generate these clocks or platform may have gpio pins which can be toggled to generate dummy clocks. This patch supports both. This patch also adds in generic bus recovery routines gpio or scl line based which can be used by bus controller. In addition controller driver may provide its own version of the bus recovery routine. This doesn't support multi-master recovery for now. Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxx> --- V4->V5: - section name corrected to 3.1.16 - merged gpio and non-gpio recovery routines to remove code redundancy - Changed types of gpio and gpio-flags to unsigned and unsigned long - Checking return value of get_gpio() now - using DIV_ROUND_UP for calculating delay, to get more correct value drivers/i2c/i2c-core.c | 153 +++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/i2c.h | 52 +++++++++++++++++ 2 files changed, 205 insertions(+) diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c index a7edf98..bdc249a 100644 --- a/drivers/i2c/i2c-core.c +++ b/drivers/i2c/i2c-core.c @@ -27,7 +27,9 @@ #include <linux/module.h> #include <linux/kernel.h> +#include <linux/delay.h> #include <linux/errno.h> +#include <linux/gpio.h> #include <linux/slab.h> #include <linux/i2c.h> #include <linux/init.h> @@ -104,6 +106,116 @@ static int i2c_device_uevent(struct device *dev, struct kobj_uevent_env *env) #define i2c_device_uevent NULL #endif /* CONFIG_HOTPLUG */ +/* i2c bus recovery routines */ +static inline void set_scl_value(struct i2c_adapter *adap, int val) +{ + struct i2c_bus_recovery_info *bri = adap->bus_recovery_info; + + if (bri->is_gpio_recovery) + gpio_set_value(bri->scl_gpio, val); + else + bri->set_scl(adap, val); +} + +static inline int get_sda_value(struct i2c_adapter *adap) +{ + struct i2c_bus_recovery_info *bri = adap->bus_recovery_info; + + if (bri->is_gpio_recovery) + return gpio_get_value(bri->sda_gpio); + else + return bri->get_sda(adap); +} + +static int i2c_get_gpios_for_recovery(struct i2c_adapter *adap) +{ + struct i2c_bus_recovery_info *bri = adap->bus_recovery_info; + struct device *dev = &adap->dev; + int ret = 0; + + if (bri->get_gpio) { + ret = bri->get_gpio(bri->scl_gpio); + if (ret) { + dev_warn(dev, "scl get_gpio: %d\n", bri->scl_gpio); + return ret; + } + } + + ret = gpio_request_one(bri->scl_gpio, bri->scl_gpio_flags, "i2c-scl"); + if (ret) { + dev_warn(dev, "gpio request fail: %d\n", bri->scl_gpio); + goto scl_put_gpio; + } + + if (!bri->skip_sda_polling) { + if (bri->get_gpio) + ret = bri->get_gpio(bri->sda_gpio); + + if (unlikely(ret || + gpio_request_one(bri->sda_gpio, bri->sda_gpio_flags, + "i2c-sda"))) { + /* work without sda polling */ + dev_warn(dev, "can't get sda: %d. Skip sda polling\n", + bri->sda_gpio); + bri->skip_sda_polling = true; + if (!ret && bri->put_gpio) + bri->put_gpio(bri->sda_gpio); + + ret = 0; + } + } + +scl_put_gpio: + if (bri->put_gpio) + bri->put_gpio(bri->scl_gpio); + + return ret; +} + +static void i2c_put_gpios_for_recovery(struct i2c_adapter *adap) +{ + struct i2c_bus_recovery_info *bri = adap->bus_recovery_info; + + gpio_free(bri->scl_gpio); + + if (!bri->skip_sda_polling) { + gpio_free(bri->sda_gpio); + + if (bri->put_gpio) + bri->put_gpio(bri->sda_gpio); + } +} + +static int i2c_recover_bus(struct i2c_adapter *adap) +{ + struct i2c_bus_recovery_info *bri = adap->bus_recovery_info; + unsigned long delay = 1000000; + int i, ret, val = 1; + + if (bri->is_gpio_recovery) { + ret = i2c_get_gpios_for_recovery(adap); + if (ret) + return ret; + } + + delay = DIV_ROUND_UP(delay, bri->clock_rate_khz * 2); + + for (i = 0; i < bri->clock_cnt * 2; i++, val = !val) { + set_scl_value(adap, val); + ndelay(delay); + + /* break if sda got high, check only when scl line is high */ + if (!bri->skip_sda_polling && val) + if (unlikely(get_sda_value(adap))) + break; + } + + if (bri->is_gpio_recovery) + i2c_put_gpios_for_recovery(adap); + + return 0; +} + static int i2c_device_probe(struct device *dev) { struct i2c_client *client = i2c_verify_client(dev); @@ -896,6 +1008,47 @@ static int i2c_register_adapter(struct i2c_adapter *adap) "Failed to create compatibility class link\n"); #endif + /* bus recovery specific initialization */ + if (adap->bus_recovery_info) { + struct i2c_bus_recovery_info *bri = adap->bus_recovery_info; + + if (bri->recover_bus) { + dev_info(&adap->dev, + "registered for non-generic bus recovery\n"); + } else { + /* Use generic recovery routines */ + if (!bri->clock_rate_khz) { + dev_warn(&adap->dev, + "doesn't have valid recovery clock rate\n"); + goto exit_recovery; + } + + /* Most controller need 9 clocks at max */ + if (!bri->clock_cnt) + bri->clock_cnt = 9; + + bri->recover_bus = i2c_recover_bus; + + if (bri->is_gpio_recovery) { + dev_info(&adap->dev, + "registered for gpio bus recovery\n"); + } else if (bri->set_scl) { + if (!bri->skip_sda_polling && !bri->get_sda) { + dev_warn(&adap->dev, + "!get_sda. skip sda polling\n"); + bri->skip_sda_polling = true; + } + + dev_info(&adap->dev, + "registered for scl bus recovery\n"); + } else { + dev_warn(&adap->dev, + "doesn't have valid recovery type\n"); + } + } + } + +exit_recovery: /* create pre-declared device nodes */ if (adap->nr < __i2c_first_dynamic_bus_num) i2c_scan_static_board_info(adap); diff --git a/include/linux/i2c.h b/include/linux/i2c.h index 5970266..c43e5c4 100644 --- a/include/linux/i2c.h +++ b/include/linux/i2c.h @@ -370,6 +370,55 @@ struct i2c_algorithm { u32 (*functionality) (struct i2c_adapter *); }; +/** + * struct i2c_bus_recovery_info - I2c bus recovery information + * @recover_bus: Recover routine. Either pass driver's recover_bus() routine, or + * pass it NULL to use generic ones, i.e. gpio or scl based. + * @skip_sda_polling: if true, bus recovery will not poll sda line to check if + * it became high or not. Only required if recover_bus == NULL. + * @is_gpio_recovery: true, select gpio type else scl type. Only required if + * recover_bus == NULL. + * @clock_rate_khz: clock rate of dummy clock in khz. Required for both gpio and + * scl type recovery. + * @clock_cnt: count of max clocks to be generated. Required for both gpio and + * scl type recovery. + * @set_scl: controller specific scl configuration routine. Only required if + * is_gpio_recovery == false + * @get_sda: controller specific sda read routine. Only required if + * is_gpio_recovery == false and skip_sda_polling == false. + * @get_gpio: called before recover_bus() to get padmux configured for scl line. + * as gpio. Only required if is_gpio_recovery == true. Return 0 on success. + * @put_gpio: called after recover_bus() to get padmux configured for scl line + * as scl. Only required if is_gpio_recovery == true. + * @scl_gpio: gpio number of the scl line. Only required if is_gpio_recovery == + * true. + * @sda_gpio: gpio number of the sda line. Only required if is_gpio_recovery == + * true and skip_sda_polling == false. + * @scl_gpio_flags: flag for gpio_request_one of scl_gpio. 0 implies + * GPIOF_OUT_INIT_LOW. + * @sda_gpio_flags: flag for gpio_request_one of sda_gpio. 0 implies + * GPIOF_OUT_INIT_LOW. + */ +struct i2c_bus_recovery_info { + int (*recover_bus)(struct i2c_adapter *); + bool skip_sda_polling; + bool is_gpio_recovery; + u32 clock_rate_khz; + u8 clock_cnt; + + /* scl/sda recovery */ + void (*set_scl)(struct i2c_adapter *, int val); + int (*get_sda)(struct i2c_adapter *); + + /* gpio recovery */ + int (*get_gpio)(unsigned gpio); + void (*put_gpio)(unsigned gpio); + unsigned scl_gpio; + unsigned sda_gpio; + unsigned long scl_gpio_flags; + unsigned long sda_gpio_flags; +}; + /* * i2c_adapter is the structure used to identify a physical i2c bus along * with the access algorithms necessary to access it. @@ -393,6 +442,9 @@ struct i2c_adapter { struct mutex userspace_clients_lock; struct list_head userspace_clients; + + /* Pass valid pointer if recovery infrastructure is required */ + struct i2c_bus_recovery_info *bus_recovery_info; }; #define to_i2c_adapter(d) container_of(d, struct i2c_adapter, dev) -- 1.7.12.rc2.18.g61b472e -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
