Re: Fwd: [PATCH 1/3] i2c: Add Device Tree support to the Nomadik I2C driver

[Lee Jones <lee.jones-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>]

On 15/06/12 12:50, Srinidhi Kasagar wrote:
> [...]
>>
>>
>> From: Lee Jones<lee.jones-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
>> Date: Tue, 17 Apr 2012 16:04:13 +0100
>> Subject: [PATCH 1/1] i2c: Add Device Tree support to the Nomadik I2C driver
>>
>> Here we apply the bindings required for successful Device Tree
>> probing of the i2c-nomadik driver. We also apply a fall-back
>> configuration in case either one is not provided, or a required
>> element is missing from the one supplied.
>>
>> Cc: linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
>> Signed-off-by: Lee Jones<lee.jones-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
>> ---
>>   drivers/i2c/busses/i2c-nomadik.c |   82 +++++++++++++++++++++++++++++++++++++-
>>   1 file changed, 80 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/i2c/busses/i2c-nomadik.c b/drivers/i2c/busses/i2c-nomadik.c
>> index a92440d..58e8114 100644
>> --- a/drivers/i2c/busses/i2c-nomadik.c
>> +++ b/drivers/i2c/busses/i2c-nomadik.c
>> @@ -23,6 +23,7 @@
>>   #include<linux/io.h>
>>   #include<linux/regulator/consumer.h>
>>   #include<linux/pm_runtime.h>
>> +#include<linux/of.h>
>>
>>   #include<plat/i2c.h>
>>
>> @@ -899,15 +900,86 @@ static const struct i2c_algorithm nmk_i2c_algo = {
>>         .functionality  = nmk_i2c_functionality
>>   };
>>
>> +static struct nmk_i2c_controller u8500_i2c = {
>> +       /*
>> +        * Slave data setup time; 250ns, 100ns, and 10ns, which
>> +        * is 14, 6 and 2 respectively for a 48Mhz i2c clock.
>> +        */
>> +       .slsu           = 0xe,
>> +       .tft            = 1,      /* Tx FIFO threshold */
>> +       .rft            = 8,      /* Rx FIFO threshold */
>> +       .clk_freq       = 100000, /* std. mode operation */
>> +       .timeout        = 200,    /* Slave response timeout(ms) */
>> +       .sm             = I2C_FREQ_MODE_FAST,
>
> How is this possible? you are setting clk_freq as 100kb/s and mode
> as fast mode which is supposed to be 400kb/s.

That's not how I read it:

> enum i2c_freq_mode {
>         I2C_FREQ_MODE_STANDARD,         /* up to 100 Kb/s */
>         I2C_FREQ_MODE_FAST,             /* up to 400 Kb/s */
>         I2C_FREQ_MODE_HIGH_SPEED,       /* up to 3.4 Mb/s */
>         I2C_FREQ_MODE_FAST_PLUS,        /* up to 1 Mb/s */
> };

The operative words here are "up to".

>> +};
>> +
>> +static int __devinit
>> +nmk_i2c_of_probe(struct device_node *np, struct nmk_i2c_controller *pdata)
>> +{
>> +       of_property_read_u32(np, "clock-frequency", (u32*)&pdata->clk_freq);
>> +       if (!pdata->clk_freq) {
>> +               pr_warn("%s: Clock frequency not found\n", np->full_name);
>> +               return -EINVAL;
>> +       }
>> +
>> +       of_property_read_u32(np, "stericsson,slsu", (u32*)&pdata->slsu);
>> +       if (!pdata->slsu) {
>> +               pr_warn("%s: Data line delay not found\n", np->full_name);
>> +               return -EINVAL;
>> +       }
>> +
>> +       of_property_read_u32(np, "stericsson,tft", (u32*)&pdata->tft);
>> +       if (!pdata->tft) {
>> +               pr_warn("%s: Tx FIFO threshold not found\n", np->full_name);
>> +               return -EINVAL;
>> +       }
>> +
>> +       of_property_read_u32(np, "stericsson,rft", (u32*)&pdata->rft);
>> +       if (!pdata->rft) {
>> +               pr_warn("%s: Rx FIFO threshold not found\n", np->full_name);
>> +               return -EINVAL;
>> +       }
>> +
>> +       of_property_read_u32(np, "stericsson,timeout", (u32*)&pdata->timeout);
>> +       if (!pdata->timeout) {
>> +               pr_warn("%s: Timeout not found\n", np->full_name);
>> +               return -EINVAL;
>> +       }
>> +
>> +       if (of_get_property(np, "stericsson,i2c_freq_mode_fast", NULL))
>> +               pdata->sm = I2C_FREQ_MODE_FAST;
>> +       else
>> +               pdata->sm = I2C_FREQ_MODE_STANDARD;
>
> The controller has more modes like fast mode plus and high speed mode. You can't make
> assumptions like this.

These are currently unsupported. Read the comments in the file:

> 	/*
> 	 * set the speed mode. Currently we support
> 	 * only standard and fast mode of operation
> 	 * TODO - support for fast mode plus (up to 1Mb/s)
> 	 * and high speed (up to 3.4 Mb/s)
> 	 */

I can add a similar comment here if it make you feel better?

>> +
>> +       return 0;
>> +}
>> +
>>   static int __devinit nmk_i2c_probe(struct platform_device *pdev)
>>   {
>>         int ret = 0;
>>         struct resource *res;
>> -       struct nmk_i2c_controller *pdata =
>> -                       pdev->dev.platform_data;
>> +       struct nmk_i2c_controller *pdata = pdev->dev.platform_data;
>> +       struct device_node *np = pdev->dev.of_node;
>>         struct nmk_i2c_dev      *dev;
>>         struct i2c_adapter *adap;
>>
>> +       if (np) {
>> +               if (!pdata) {
>> +                       pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
>> +                       if (!pdata) {
>> +                               ret = -ENOMEM;
>> +                               goto err_no_mem;
>> +                       }
>> +               }
>> +               ret = nmk_i2c_of_probe(np, pdata);
>> +               if (ret)
>> +                       kfree(pdata);
>> +       }
>> +
>> +       if (!pdata)
>> +               /* No i2c configuration found, using the default. */
>> +               pdata =&u8500_i2c;
>
> There are redundant fallback configurations exists in the driver. You might need to remove
> those, if you want to fallback here.

I only see a fall-back for clk_freq. Are there others?

>> +
>>         dev = kzalloc(sizeof(struct nmk_i2c_dev), GFP_KERNEL);
>>         if (!dev) {
>>                 dev_err(&pdev->dev, "cannot allocate memory\n");
>> @@ -1038,11 +1110,17 @@ static int __devexit nmk_i2c_remove(struct platform_device *pdev)
>>         return 0;
>>   }
>>
>> +static const struct of_device_id nmk_gpio_match[] = {
>> +       { .compatible = "st,nomadik-i2c", },
>> +       {},
>> +};
>> +
>>   static struct platform_driver nmk_i2c_driver = {
>>         .driver = {
>>                 .owner = THIS_MODULE,
>>                 .name = DRIVER_NAME,
>>                 .pm =&nmk_i2c_pm,
>> +               .of_match_table = nmk_gpio_match,
>>         },
>>         .probe = nmk_i2c_probe,
>>         .remove = __devexit_p(nmk_i2c_remove),
>> --
>> 1.7.9.5
>>

Kind regards,
Lee

-- 
Lee Jones
Linaro ST-Ericsson Landing Team Lead
M: +44 77 88 633 515
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog