On Mon, Aug 27, 2012 at 10:41:26AM +0530, Viresh Kumar wrote: > From: Viresh Kumar <viresh.kumar@xxxxxx> > > Add i2c bus recovery infrastructure to i2c adapters as specified in the i2c > protocol Rev. 03 section 3.16 titled "Bus clear". It's 3.1.16, not 3.16. > 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. > > Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxx> > --- > drivers/i2c/i2c-core.c | 125 +++++++++++++++++++++++++++++++++++++++++++++++++ > include/linux/i2c.h | 52 ++++++++++++++++++++ > 2 files changed, 177 insertions(+) > > diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c > index 96ef3d8..7ede75d 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 +106,88 @@ 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 int i2c_gpio_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->get_gpio) > + bri->get_gpio(bri->scl_gpio); get_gpio returns an int. That should be checked. > + ret = gpio_request_one(bri->scl_gpio, bri->scl_gpio_flags, "i2c-scl"); > + if (ret < 0) { > + dev_warn(&adap->dev, "gpio request fail: %d\n", bri->scl_gpio); > + return ret; > + } > + > + if (!bri->skip_sda_polling) { > + if (bri->get_gpio) > + bri->get_gpio(bri->sda_gpio); ditto. > + > + ret = gpio_request_one(bri->sda_gpio, bri->sda_gpio_flags, > + "i2c-sda"); > + if (ret < 0) { > + /* work without sda polling */ > + dev_warn(&adap->dev, > + "sda_gpio request fail: %d. Skip sda polling\n", > + bri->scl_gpio); > + bri->skip_sda_polling = true; > + if (bri->put_gpio) > + bri->put_gpio(bri->sda_gpio); > + } > + } > + > + delay /= bri->clock_rate_khz * 2; For maximal correctness you should use DIV_ROUND_UP here. > + > + for (i = 0; i < bri->clock_cnt * 2; i++, val = !val) { When do you want clock_cnt != 9? > + ndelay(delay); > + gpio_set_value(bri->scl_gpio, val); > + > + /* break if sda got high, check only when scl line is high */ > + if (!bri->skip_sda_polling && val) > + if (gpio_get_value(bri->sda_gpio)) > + break; I'm not sure it's worth to conditionally shortcut here. Either always or never shortcut. In a document by Atmel describing on of their at24 eeproms they suggest to send an start and stop after the nine clocks. Yesterday I considered that sensible but today I don't remember why. Also it might be worth pointing out that this procedure isn't multi-master save because it does neither clock synchronization (3.1.7) nor arbitration (3.1.8). I'm not sure how relevant multi-master is, but if you don't consider it maybe still make it explicit. > + } > + > + gpio_free(bri->scl_gpio); > + > + if (bri->put_gpio) > + bri->put_gpio(bri->scl_gpio); > + > + if (!bri->skip_sda_polling) { > + gpio_free(bri->sda_gpio); > + > + if (bri->put_gpio) > + bri->put_gpio(bri->sda_gpio); > + } > + > + return 0; > +} > + > +static int i2c_scl_recover_bus(struct i2c_adapter *adap) > +{ > + struct i2c_bus_recovery_info *bri = adap->bus_recovery_info; > + int i, val = 0; > + unsigned long delay = 1000000; > + > + delay /= bri->clock_rate_khz * 2; > + > + for (i = 0; i < bri->clock_cnt * 2; i++, > + val = !val) { > + bri->set_scl(adap, val); again for multi-master set_scl can fail and so if this scenario is considered worth to be supported it should return an error indication that needs handling. > + ndelay(delay); > + > + /* break if sda got high, check only when scl line is high */ > + if (!bri->skip_sda_polling && val) > + if (bri->get_sda(adap)) > + break; > + } > + > + return 0; > +} i2c_scl_recover_bus and i2c_gpio_recover_bus have a common pattern. Both bitbang SCL and SDA. Is it worth to factor out the common stuff? > + > static int i2c_device_probe(struct device *dev) > { > struct i2c_client *client = i2c_verify_client(dev); > @@ -879,6 +963,47 @@ 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; > + > + if (bri->is_gpio_recovery) { > + bri->recover_bus = i2c_gpio_recover_bus; > + 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; > + } > + > + bri->recover_bus = i2c_scl_recover_bus; > + 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..9e0a14a 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. This is used for both, scl and sda. I don't know if there is a more modern approach available using the pinmux framework? (Added Linus Walleij to Cc.) > + * @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. IMHO you should not make this configurable but use GPIOF_OUT_INIT_HIGH | GPIOF_OPEN_DRAIN > + * @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); > + int (*put_gpio)(unsigned gpio); > + u32 scl_gpio; > + u32 sda_gpio; > + u32 scl_gpio_flags; > + u32 sda_gpio_flags; These are not the right types. gpio_request_one expects gpio to be unsigned and flags to be unsigned long. As scl/sda recovery and gpio recovery are mutually exclusive you could use a union here. But maybe it's not worth the added complexity? > +}; > + > /* > * 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) Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | http://www.pengutronix.de/ | -- 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
