On Fri, Mar 02, 2012 at 11:53:42AM +0530, Viresh Kumar wrote: > Add i2c bus recovery infrastructure to i2c adapters as specified in the i2c > protocol Rev. 03 section 3.16 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. > > Signed-off-by: Viresh Kumar <[email protected]>
Finally, a review \o/
There are some comments regarding the code, but the most important thing
is to get the interface right.
Jean, I don't think this is embedded only, so an additional view might
be helpful here.
Linus, can you have a look wearing your pinmux/pinctrl hat? This
functionality may need to switch SDA/SCL pins to GPIOs so they can be
manually clocked. I'd think this is a prime example for pinmux, but am
unsure if we should rely on it only. Is it enforced for active
platforms?
> ---
> drivers/i2c/i2c-core.c | 125
> ++++++++++++++++++++++++++++++++++++++++++++++++
> include/linux/i2c.h | 52 ++++++++++++++++++++
> 2 files changed, 177 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
> index e9c1893..5cd5f83 100644
> --- a/drivers/i2c/i2c-core.c
> +++ b/drivers/i2c/i2c-core.c
> @@ -26,7 +26,9 @@
>
> #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>
> @@ -103,6 +105,88 @@ 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;
I think something alike 'recov_info' is more readable than 'bri'.
> + unsigned long delay = 1000000;
udelay?
> + int i, ret, val = 1;
> +
> + if (bri->get_gpio)
> + bri->get_gpio(bri->scl_gpio);
> +
> + 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);
> +
> + 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 (i = 0; i < bri->clock_cnt * 2; i++, val = !val) {
> + 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;
> + }
> +
> + 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);
> + 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;
> +}
We have two recover bus functions here. I think it would be better to
have only one. set_scl and get_sda can be mapped to helper functions
doing needed gpio-calls during init. Something like this pseudo-code:
if (!bri->set_scl && we_have_a_scl_gpio)
set_scl = i2c_set_scl_via_gpio()
> +
> static int i2c_device_probe(struct device *dev)
> {
> struct i2c_client *client = i2c_verify_client(dev);
> @@ -861,6 +945,47 @@ 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");
Printouts here should probably be dev_dbg (if not left out), most users
won't care.
> + }
> + }
> + }
> +
> +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 8e25a91..1310d1a 100644
> --- a/include/linux/i2c.h
> +++ b/include/linux/i2c.h
> @@ -365,6 +365,55 @@ struct i2c_algorithm {
> u32 (*functionality) (struct i2c_adapter *);
> };
>
The description of the members is a good start. To be complete, I'd think
we need some higher level description in Documentation/i2c, too, with an
example how to set up.
> +/**
> + * 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.
Assume this when there is no get_sda() and/or SDA GPIO defined?
> + * @is_gpio_recovery: true, select gpio type else scl type. Only required if
> + * recover_bus == NULL.
Assume this when there is no GPIO defined (and no recover_bus)?
> + * @clock_rate_khz: clock rate of dummy clock in khz. Required for both gpio
> and
> + * scl type recovery.
Hrmm, current bus speed should really be in i2c_adapter somewhen. Not
your problem, though (unless you want it to be :)) Jean, what do you
think?
> + * @clock_cnt: count of max clocks to be generated. Required for both gpio
> and
> + * scl type recovery.
Why should that be different from 9 (as said in the docs)?
> + * @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.
> + * @put_gpio: called after recover_bus() to get padmux configured for scl
> line
> + * as scl. Only required if is_gpio_recovery == true.
Can't we use the pinmux/pinctrl subsystem here? Not knowing too much
about it, CCing Linus.
> + * @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.
For the last 4, I'd suggest to pass a struct gpio scl_sda_gpio_array[2]
or something.
> + */
> +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;
> +};
> +
> /*
> * i2c_adapter is the structure used to identify a physical i2c bus along
> * with the access algorithms necessary to access it.
> @@ -388,6 +437,9 @@ 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)
>
I'd also think calling the recover function should be in the core and
not in all the drivers.
Regards,
Wolfram
--
Pengutronix e.K. | Wolfram Sang |
Industrial Linux Solutions | http://www.pengutronix.de/ |
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