[PATCH 3/4] mmc: mediatek: Add tune support

[Chaotian Jing]

On Thu, 2015-10-15 at 08:29 +0200, Sascha Hauer wrote:
> Hi,
> 
> On Tue, Oct 13, 2015 at 05:37:57PM +0800, Chaotian Jing wrote:
> > @@ -1260,6 +1547,16 @@ static int msdc_drv_probe(struct platform_device *pdev)
> >  		goto host_free;
> >  	}
> >  
> > +	host->src_clk_parent = clk_get_parent(host->src_clk);
> > +	host->hs400_src = devm_clk_get(&pdev->dev, "400mhz");
> > +	if (IS_ERR(host->hs400_src)) {
> > +		dev_dbg(&pdev->dev, "Cannot find 400mhz at dts!\n");
> > +	} else if (clk_set_parent(host->src_clk_parent, host->hs400_src) < 0) {
> > +		dev_err(host->dev, "Failed to set 400mhz source clock!\n");
> > +		ret = -EINVAL;
> > +		goto host_free;
> > +	}
> 
> This is a static setup. We have device tree bindings for doing this.
> Please look for assigned-clocks and assigned-clock-parents. Doing stuff
> like this in the driver almost certainly leads to problems because the
> next SoC will have different requirements here.
> 

Sorry, I cannot understand it, could you help to give some sample code
about this ?

note the "host->src_clk" is only a clock gate, so must get its
parent(PLL), And, I tried to use clk_set_rate, but it will fail
in our platform, because may be more than one parent have the same clock
frequency. So, use the clk_set_parent to specify it's parent.

> Sascha
>