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SubjectRe: [PATCH] i2c-designware: add i2c gpio recovery option
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G'day Andy,

Thanks for the review.

On 10/05/2017 21:13, Andy Shevchenko wrote:
> On Wed, 2017-05-10 at 13:57 +0200, Tim Sander wrote:
>> This patch contains much input from Phil Reid and has been tested
>> on Intel/Altera Cyclone V SOC Hardware with Altera GPIO's for the
>> SCL and SDA GPIO's. I am still a little unsure about the recover
>> in the timeout case (i2c-designware-core.c:770) as i could not
>> test this codepath.
>
> Since it's not an RFC anymore let me do some comments on the below.
>
>> @@ -317,6 +317,7 @@ static void i2c_dw_release_lock(struct dw_i2c_dev
>> *dev)
>> dev->release_lock(dev);
>> }
>>
>> +
>> /**
>> * i2c_dw_init() - initialize the designware i2c master hardware
>> * @dev: device private data
>
> This doesn't belong to the change.
>
>> @@ -463,7 +464,12 @@ static int i2c_dw_wait_bus_not_busy(struct
>> dw_i2c_dev *dev)
>> while (dw_readl(dev, DW_IC_STATUS) & DW_IC_STATUS_ACTIVITY) {
>
>> if (timeout <= 0) {
>> dev_warn(dev->dev, "timeout waiting for bus
>> ready\n");
>> - return -ETIMEDOUT;
>> + i2c_recover_bus(&dev->adapter);
>> +
>> + if (dw_readl(dev, DW_IC_STATUS) &
>> DW_IC_STATUS_ACTIVITY)
>> + return -ETIMEDOUT;
>
>> + else
>
> Redundant.
>
>> + return 0;
>> }
>
> Actually I would rather refactor first above function:
> 1) to be do {} while();
> 2) to have invariant condition out of the loop.
>
>> timeout--;
>> usleep_range(1000, 1100);
>
>> @@ -719,9 +725,10 @@ static int i2c_dw_handle_tx_abort(struct
>> dw_i2c_dev *dev)
>> for_each_set_bit(i, &abort_source, ARRAY_SIZE(abort_sources))
>> dev_err(dev->dev, "%s: %s\n", __func__,
>> abort_sources[i]);
>>
>> - if (abort_source & DW_IC_TX_ARB_LOST)
>> + if (abort_source & DW_IC_TX_ARB_LOST) {
>> + i2c_recover_bus(&dev->adapter);
>> return -EAGAIN;
>
>> - else if (abort_source & DW_IC_TX_ABRT_GCALL_READ)
>> + } else if (abort_source & DW_IC_TX_ABRT_GCALL_READ)
>> return -EINVAL; /* wrong msgs[] data */
>> else
>
> Both else:s are redundant.
>
> if (abort_source & DW_IC_TX_ARB_LOST) {
> i2c_recover_bus(&dev->adapter);
> return -EAGAIN;
> }
>
> if (abort_source & DW_IC_TX_ABRT_GCALL_READ)
> ...
>
> Though I may agree on leaving them here for sake of keeping less lines
> of code.
>
>> return -EIO;
>
>> +#include <linux/gpio.h>
>
> I think it should be
>
> #include <linux/gpio/consumer.h>
>
>> --- a/drivers/i2c/busses/i2c-designware-platdrv.c
>> +++ b/drivers/i2c/busses/i2c-designware-platdrv.c
>> @@ -41,6 +41,7 @@
>> #include <linux/reset.h>
>> #include <linux/slab.h>
>> #include <linux/acpi.h>
>
>> +#include <linux/of_gpio.h>
>
> No, please don't.
>
> In recent code we try to avoid OF/ACPI/platform specific bits if there
> is a common resource provider (and API) for that. GPIO is the case.
>
>> +void i2c_dw_unprepare_recovery(struct i2c_adapter *adap)
>> +{
>
>> +}
>> +
>> +
>
> Remove extra line.
>
>> +static int i2c_dw_get_scl(struct i2c_adapter *adap)
>> +{
>> + struct platform_device *pdev = to_platform_device(&adap->dev);
>> + struct dw_i2c_dev *dev = platform_get_drvdata(pdev);
>
> struct dw_i2c_dev *dev = i2c_get_adapdata(adap); ?
>
> Ditto for all occurrences in the code.
>
>> +
>> + return gpiod_get_value_cansleep(dev->gpio_scl);
>> +}
>
>> +static int i2c_dw_init_recovery_info(struct dw_i2c_dev *dev,
>> + struct i2c_adapter *adap)
>> +{
>> + struct i2c_bus_recovery_info *rinfo = &dev->rinfo;
>> +
>> + dev->gpio_scl = devm_gpiod_get_optional(dev->dev,
>> + "scl",
>> + GPIOD_OUT_HIGH);
>
>> + if (IS_ERR_OR_NULL(dev->gpio_scl))
>
> This is wrong. You should not use this macro in most cases. And
> especially it breaks the logic behind _optional().
My logic here was that if the gpio is optional return null we return 0.
which is an okay status.
But this breaks if !CONFIG_GPIOLIB, which I keep forgetting. I've never
quite wrapped my head around why that's the case.

But the probe function only bails out if this returns EPROBE_DEFER.
Not sure that's the best approach

>
>> + return PTR_ERR(dev->gpio_scl);
>> +
>> + dev->gpio_sda = devm_gpiod_get_optional(dev->dev, "sda",
>> GPIOD_IN);
>
>> + if (IS_ERR_OR_NULL(dev->gpio_sda))
>
> Ditto.
>
>> + return PTR_ERR(dev->gpio_sda);
>
>> + rinfo->scl_gpio = desc_to_gpio(dev->gpio_scl);
>> + rinfo->sda_gpio = desc_to_gpio(dev->gpio_sda);
>
> Why?!
From my first attempt, didn't remove it from the example I sent.

We could change i2c_init_recovery to something like the following
then the gpio set / getter could use the default functions.
Not sure the code is completely correct but hopefully you get the concept.

static void i2c_init_recovery(struct i2c_adapter *adap)
{
struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
char *err_str;

if (!bri)
return;

if (!bri->recover_bus) {
err_str = "no recover_bus() found";
goto err;
}

/* bail out if either no gpio or no set/get callback. */
if (!gpio_is_valid(bri->scl_gpio) && (!bri->set_scl || !bri->get_scl)) {
if (!gpio_is_valid(bri->scl_gpio))
err_str = "invalid SCL gpio";
else
err_str = "no {get|set}_scl() found";
goto err;
}

if (gpio_is_valid(bri->sda_gpio))
bri->get_sda = get_sda_gpio_value;

if (gpio_is_valid(bri->scl_gpio)) {
bri->get_scl = get_scl_gpio_value;
bri->set_scl = set_scl_gpio_value;
}

return;
err:
dev_err(&adap->dev, "Not using recovery: %s\n", err_str);
adap->bus_recovery_info = NULL;
}



>
>> +};
>
>> @@ -285,6 +368,7 @@ static int dw_i2c_plat_probe(struct
>> platform_device *pdev)
>> adap->class = I2C_CLASS_DEPRECATED;
>> ACPI_COMPANION_SET(&adap->dev, ACPI_COMPANION(&pdev->dev));
>> adap->dev.of_node = pdev->dev.of_node;
>> + snprintf(adap->name, sizeof(adap->name), "Designware i2c
>> adapter");
>
> It looks like a separate change.
>
>>
>> + r = i2c_dw_init_recovery_info(dev, adap);
>> + if (r == -EPROBE_DEFER)
>
> Remove extra space.
>
>> + goto exit_probe;
>> +
>> r = i2c_dw_probe(dev);
>> if (r)
>> goto exit_probe;
>>
>
>> - return r;
>> + return 0;
>
> Doesn't belong to the change.
>
> Don't change arbitrary typos or do small "improvements" in the change
> which is not about them.
>


--
Regards
Phil Reid

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