Re: [PATCH] i2c: designware: Do not require clock when SSCN and FFCN are provided

[Suravee Suthikulpanit]

On 12/16/2015 08:28 AM, Mika Westerberg wrote:
> On Wed, Dec 16, 2015 at 08:11:12AM -0600, Suravee Suthikulpanit wrote:
> > > The clk framework should work fine if the returned clock is NULL (which
> > > I think is your case).
> > >
> > > The driver gates clocks when the device is suspended and on Intel LPSS
> > > there actually is a clock that gets gated.
> > >
> > > > [..]
> > > > @@ -203,13 +223,11 @@ static int dw_i2c_plat_probe(struct platform_device *pdev)
> > > >   		dev->master_cfg =  DW_IC_CON_MASTER | DW_IC_CON_SLAVE_DISABLE |
> > > >   			DW_IC_CON_RESTART_EN | DW_IC_CON_SPEED_FAST;
> > > >
> > > > -	dev->clk = devm_clk_get(&pdev->dev, NULL);
> > > > -	dev->get_clk_rate_khz = i2c_dw_get_clk_rate_khz;
> > > > -	if (IS_ERR(dev->clk))
> > > > -		return PTR_ERR(dev->clk);
> >
> > Actually, if we don't provide the clock (which is the case for ACPI), this
> > would also return and cause the probing to fail.
>
> Indeed it seems that when you have CONFIG_COMMON_CLK selected the clock
> framework starts returning errors if the clock is not found.
>
> Since we need the clock for Intel LPSS I2C host controllers (and they
> may have *CNT methods), I think you just need to provide the clock for
> AMD I2C host controller in similar way than we do in
> drivers/acpi/acpi_lpss.c.

I am trying to avoid having to hard-coded clock frequency value in the 
driver. Would it be alright to not return w/ error, and just do the 
following?

	dev->clk = devm_clk_get(&pdev->dev, NULL);
	if (!IS_ERR(dev->clk))
		dev->get_clk_rate_khz = i2c_dw_get_clk_rate_khz;

This should work for the Intel case when clock is also provided.

Thanks,
Suravee
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/