Re: [PATCH v2 03/11] ARM: davinci: da850: use clk->set_parent for async3

[David Lechner]

On 03/23/2016 10:56 AM, Sekhar Nori wrote:
> On Thursday 17 March 2016 07:56 AM, David Lechner wrote:
> > The da850 family of processors has an async3 clock domain that can be
> > muxed to either pll0_sysclk2 or pll1_sysclk2. Now that the davinci clocks
> > have a set_parent callback, we can use this to control the async3 mux
> > instead of a stand-alone function.
> >
> > This adds a new async3_clk and sets the appropriate child clocks. The
> > default is use to pll1_sysclk2 since it is not affected by processor
> > frequency scaling.
> >
> > Signed-off-by: David Lechner <david@xxxxxxxxxxxxxx>
> > ---
>
> > +static int da850_async3_set_parent(struct clk *clk, struct clk *parent)
> > +{
> > +	u32 __iomem *cfgchip3;
> > +	u32 val;
> > +
> > +	/*
> > +	 * Can't use DA8XX_SYSCFG0_VIRT() here since this can be called before
> > +	 * da8xx_syscfg0_base is initialized.
> > +	 */
> > +	cfgchip3 = ioremap(DA8XX_SYSCFG0_BASE + DA8XX_CFGCHIP3_REG, 4);
>
> Is this just a theoretical possibility or have you seen this happen? I
> would like to see if there are ways of avoiding this rather than throw
> away usage of DA8XX_SYSCFG0_VIRT()

Yes, it will not boot without this. The problem comes from the fact that 
clocks are setup in davinci_common_init() which is called before 
da8xx_syscfg0_base = ioremap(DA8XX_SYSCFG0_BASE, SZ_4K) in da850_init() 
(and da830_init()). I also tried moving the ioremap() before 
davinci_common_init(), but davinci_common_init() sets up the iomem, so 
that doesn't work either.

So, if you want to use DA8XX_SYSCFG0_VIRT() here, the clock init would 
have to be split out from davinci_common_init() which would affect all 
davinci devices.