From: Uwe Kleine-König <mailto:[email protected]> Sent: Tuesday,
July 14, 2015 2:49 PM
> To: Gao Pan-B54642
> Cc: [email protected]; [email protected]; Li Frank-B20596; Duan
> Fugang-B38611
> Subject: Re: [Patch v1] i2c: imx: implement bus recovery
>
> Hello Gao,
>
> On Tue, Jul 14, 2015 at 10:04:46AM +0800, Gao Pan wrote:
> > Implement bus recovery methods for i2c-imx so we can recover from
> > situations where SCL/SDA are stuck low.
> >
> > Once i2c bus SCL/SDA are stuck low during transfer, config the i2c
> > pinctrl to gpio mode by calling pinctrl sleep set function, and then
> > use GPIO to emulate the i2c protocol to send nine dummy clock to
> > recover i2c device. After recovery, set i2c pinctrl to default group
> setting.
> >
> > Signed-off-by: Fugang Duan <[email protected]>
> > Signed-off-by: Gao Pan <[email protected]>
> > ---
> > Documentation/devicetree/bindings/i2c/i2c-imx.txt | 4 +
> > drivers/i2c/busses/i2c-imx.c | 102
> +++++++++++++++++++++-
> > 2 files changed, 105 insertions(+), 1 deletion(-)
> >
> > diff --git a/Documentation/devicetree/bindings/i2c/i2c-imx.txt
> > b/Documentation/devicetree/bindings/i2c/i2c-imx.txt
> > index ce4311d..0a0848f5 100644
> > --- a/Documentation/devicetree/bindings/i2c/i2c-imx.txt
> > +++ b/Documentation/devicetree/bindings/i2c/i2c-imx.txt
> > @@ -14,6 +14,8 @@ Optional properties:
> > The absence of the propoerty indicates the default frequency 100 kHz.
> > - dmas: A list of two dma specifiers, one for each entry in dma-names.
> > - dma-names: should contain "tx" and "rx".
> > +- recover-scl: specify the gpio related to SCL pin
> > +- recover-sda: specify the gpio related to SDA pin
> I don't like the naming here. That the gpios are used for recovery isn't
> a hardware description. What about "scl-gpio" and "sda-gpio"?
Thanks. I will change it in the next version.
> > Examples:
> >
> > @@ -37,4 +39,6 @@ i2c0: i2c@40066000 { /* i2c0 on vf610 */
> > dmas = <&edma0 0 50>,
> > <&edma0 0 51>;
> > dma-names = "rx","tx";
> > + recover-scl = <&gpio5 26 0>;
> > + recover-sda = <&gpio5 27 0>;
> > };
> > diff --git a/drivers/i2c/busses/i2c-imx.c
> > b/drivers/i2c/busses/i2c-imx.c index 785aa67..eb4f95c 100644
> > --- a/drivers/i2c/busses/i2c-imx.c
> > +++ b/drivers/i2c/busses/i2c-imx.c
> > @@ -40,6 +40,7 @@
> > #include <linux/dmapool.h>
> > #include <linux/err.h>
> > #include <linux/errno.h>
> > +#include <linux/gpio.h>
> > #include <linux/i2c.h>
> > #include <linux/init.h>
> > #include <linux/interrupt.h>
> > @@ -48,6 +49,7 @@
> > #include <linux/module.h>
> > #include <linux/of.h>
> > #include <linux/of_device.h>
> > +#include <linux/of_gpio.h>
> > #include <linux/of_dma.h>
> > #include <linux/platform_data/i2c-imx.h> #include
> > <linux/platform_device.h> @@ -175,6 +177,16 @@ enum imx_i2c_type {
> > VF610_I2C,
> > };
> >
> > +enum imx_i2c_vol_level {
> > + I2C_IMX_LOW_VOL_LEVEL,
> > + I2C_IMX_HIGH_VOL_LEVEL,
> > +};
> These are used as return value for the get_scl and get_sda callbacks
> which should return an int. I'd use plain 0 and 1 here.
Thanks. It can improve the readability to use plain 0 and 1 here.
> > +struct imx_i2c_pinctrl {
> > + unsigned int sda_pin;
> > + unsigned int scl_pin;
> > +};
> > +
> > struct imx_i2c_hwdata {
> > enum imx_i2c_type devtype;
> > unsigned regshift;
> > @@ -206,6 +218,7 @@ struct imx_i2c_struct {
> > unsigned int ifdr; /* IMX_I2C_IFDR */
> > unsigned int cur_clk;
> > unsigned int bitrate;
> > + struct imx_i2c_pinctrl pins;
> > const struct imx_i2c_hwdata *hwdata;
> >
> > struct imx_i2c_dma *dma;
> > @@ -436,7 +449,7 @@ static int i2c_imx_bus_busy(struct imx_i2c_struct
> *i2c_imx, int for_busy)
> > if (time_after(jiffies, orig_jiffies + msecs_to_jiffies(500)))
> {
> > dev_dbg(&i2c_imx->adapter.dev,
> > "<%s> I2C bus is busy\n", __func__);
> > - return -ETIMEDOUT;
> > + return i2c_recover_bus(&i2c_imx->adapter);
>
> This looks wrong. What if the bus is still busy after the call to
> i2c_recover_bus? Also it doesn't feel right to call i2c_recover_bus just
> because the bus is busy.
In there, maybe i2c device sda is pulled low and bus is dead, so I add the bus
recovery in here.
Because there wait 500ms, it is enough long.
If the bus is still busy after recovery, it return the -EBUSY, and gpio also
cannot recover the bus, so this transfer is failed.
What do you suggest for the position to call i2c_recover_bus() ? Thanks.
> > }
> > schedule();
> > }
> > @@ -450,6 +463,7 @@ static int i2c_imx_trx_complete(struct
> > imx_i2c_struct *i2c_imx)
> >
> > if (unlikely(!(i2c_imx->i2csr & I2SR_IIF))) {
> > dev_dbg(&i2c_imx->adapter.dev, "<%s> Timeout\n", __func__);
> > + i2c_recover_bus(&i2c_imx->adapter);
> > return -ETIMEDOUT;
> ditto.
The same as above. But it is better:
return i2c_recover_bus(&i2c_imx->adapter);
> > }
> > dev_dbg(&i2c_imx->adapter.dev, "<%s> TRX complete\n", __func__); @@
> > -956,6 +970,67 @@ fail0:
> > return (result < 0) ? result : num;
> > }
> >
> > +static int i2c_imx_get_scl(struct i2c_adapter *adap) {
> > + struct imx_i2c_struct *i2c_imx;
> > +
> > + i2c_imx = container_of(adap, struct imx_i2c_struct, adapter);
> > + if (i2c_imx->pins.sda_pin && i2c_imx->pins.scl_pin)
> > + return gpio_get_value(i2c_imx->pins.scl_pin);
> > +
> > + return I2C_IMX_HIGH_VOL_LEVEL;
> > +}
> > +
> > +static int i2c_imx_get_sda(struct i2c_adapter *adap) {
> > + struct imx_i2c_struct *i2c_imx;
> > +
> > + i2c_imx = container_of(adap, struct imx_i2c_struct, adapter);
> > + if (i2c_imx->pins.sda_pin && i2c_imx->pins.scl_pin) {
> > + gpio_direction_input(i2c_imx->pins.sda_pin);
> Don't you want that call in the prepare callback?
Thanks for your precise review. I will change it in the next version.
> > + return gpio_get_value(i2c_imx->pins.sda_pin);
> > + }
> > +
> > + return I2C_IMX_HIGH_VOL_LEVEL;
> > +}
> > +
> > +static void i2c_imx_set_scl(struct i2c_adapter *adap, int val) {
> > + struct imx_i2c_struct *i2c_imx;
> > +
> > + i2c_imx = container_of(adap, struct imx_i2c_struct, adapter);
> > + if (i2c_imx->pins.sda_pin && i2c_imx->pins.scl_pin)
> > + gpio_direction_output(i2c_imx->pins.scl_pin, val);
> Please move the gpio_direction_output call to the prepare callback and
> only use gpio_set_value here.
Thank you, will change it in next version.
> > +}
> > +
> > +static void i2c_imx_prepare_recovery(struct i2c_adapter *adap) {
> > + struct imx_i2c_struct *i2c_imx;
> > +
> > + i2c_imx = container_of(adap, struct imx_i2c_struct, adapter);
> > + if (i2c_imx->pins.sda_pin && i2c_imx->pins.scl_pin)
> > + pinctrl_pm_select_sleep_state(&adap->dev);
> So the sleep state is expected to mux the pins into their gpio function?
Yes, you are right. In here, we expect the pad is muxed to gpio function.
> > +
> spare empty line
Thanks.
>
> > +}
> > +
> > +static void i2c_imx_unprepare_recovery(struct i2c_adapter *adap) {
> > + struct imx_i2c_struct *i2c_imx;
> > +
> > + i2c_imx = container_of(adap, struct imx_i2c_struct, adapter);
> > + if (i2c_imx->pins.sda_pin && i2c_imx->pins.scl_pin)
> > + pinctrl_pm_select_default_state(&adap->dev);
> > +}
> > +
> > +static struct i2c_bus_recovery_info i2c_imx_bus_recovery_info = {
> > + .get_scl = i2c_imx_get_scl,
> > + .get_sda = i2c_imx_get_sda,
> > + .set_scl = i2c_imx_set_scl,
> > + .prepare_recovery = i2c_imx_prepare_recovery,
> > + .unprepare_recovery = i2c_imx_unprepare_recovery,
> > + .recover_bus = i2c_generic_scl_recovery,
> Mixed tab and spaces used for indention (if you ask me, use a single
> space before the '=' ...
Thanks for your carefulness, I will correct it in the next version.
> > +};
> > +
> > static u32 i2c_imx_func(struct i2c_adapter *adapter) {
> > return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL @@ -1009,6 +1084,7 @@
> > static int i2c_imx_probe(struct platform_device *pdev)
> > i2c_imx->adapter.dev.parent = &pdev->dev;
> > i2c_imx->adapter.nr = pdev->id;
> > i2c_imx->adapter.dev.of_node = pdev->dev.of_node;
> > + i2c_imx->adapter.bus_recovery_info = &i2c_imx_bus_recovery_info;
> > i2c_imx->base = base;
> ... which prevents uglyness as introduce here.)
Thanks.
> >
> > /* Get I2C clock */
> > @@ -1037,6 +1113,30 @@ static int i2c_imx_probe(struct platform_device
> *pdev)
> > /* Set up adapter data */
> > i2c_set_adapdata(&i2c_imx->adapter, i2c_imx);
> >
> > + /* Init recover pins */
> > + i2c_imx->pins.sda_pin =
> > + of_get_named_gpio(pdev->dev.of_node, "recover-sda", 0);
> > + i2c_imx->pins.scl_pin =
> > + of_get_named_gpio(pdev->dev.of_node, "recover-scl", 0);
> I'd use devm_gpiod_get_optional here.
Thanks for your good suggestion. I will change it in the next version.
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