Re: [PATCH] i2c: designware: Get selected speed mode sda-hold-time via ACPI

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Tue, 2017-02-14 at 13:54 +0800, chin.yew.tan@intel.com wrote:
> From: Tan Chin Yew <chin.yew.tan@intel.com>
> 
> Sda-hold-time is an important parameter for tuning i2c to meet the
> electrical specification especially for high speed. I2C with incorrect
> sda-hold-time may cause lost arbitration error. Now, the driver is
> able to
> get sda-hold-time for all the speed supported.
> 

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

> Signed-off-by: Tan Chin Yew <chin.yew.tan@intel.com>
> ---
>  drivers/i2c/busses/i2c-designware-platdrv.c | 28
> +++++++++++++++++++++-------
>  1 file changed, 21 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c
> b/drivers/i2c/busses/i2c-designware-platdrv.c
> index 6ce4313..00c880a 100644
> --- a/drivers/i2c/busses/i2c-designware-platdrv.c
> +++ b/drivers/i2c/busses/i2c-designware-platdrv.c
> @@ -101,14 +101,28 @@ static int dw_i2c_acpi_configure(struct
> platform_device *pdev)
>  	dev->rx_fifo_depth = 32;
>  
>  	/*
> -	 * Try to get SDA hold time and *CNT values from an ACPI
> method if
> -	 * it exists for both supported speed modes.
> +	 * Try to get SDA hold time and *CNT values from an ACPI
> method for
> +	 * selected speed modes.
>  	 */
> -	dw_i2c_acpi_params(pdev, "SSCN", &dev->ss_hcnt, &dev-
> >ss_lcnt, NULL);
> -	dw_i2c_acpi_params(pdev, "FMCN", &dev->fs_hcnt, &dev-
> >fs_lcnt,
> -			   &dev->sda_hold_time);
> -	dw_i2c_acpi_params(pdev, "FPCN", &dev->fp_hcnt, &dev-
> >fp_lcnt, NULL);
> -	dw_i2c_acpi_params(pdev, "HSCN", &dev->hs_hcnt, &dev-
> >hs_lcnt, NULL);
> +	switch (dev->clk_freq) {
> +	case 100000:
> +		dw_i2c_acpi_params(pdev, "SSCN", &dev->ss_hcnt, &dev-
> >ss_lcnt,
> +				   &dev->sda_hold_time);
> +		break;
> +	case 1000000:
> +		dw_i2c_acpi_params(pdev, "FPCN", &dev->fp_hcnt, &dev-
> >fp_lcnt,
> +				   &dev->sda_hold_time);
> +		break;
> +	case 3400000:
> +		dw_i2c_acpi_params(pdev, "HSCN", &dev->hs_hcnt, &dev-
> >hs_lcnt,
> +				   &dev->sda_hold_time);
> +		break;
> +	case 400000:
> +	default:
> +		dw_i2c_acpi_params(pdev, "FMCN", &dev->fs_hcnt, &dev-
> >fs_lcnt,
> +				   &dev->sda_hold_time);
> +		break;
> +	}
>  
>  	id = acpi_match_device(pdev->dev.driver->acpi_match_table,
> &pdev->dev);
>  	if (id && id->driver_data)

-- 
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy