[U-Boot] [PATCH v2 1/9] sunxi: initial sun7i clocks and timer support.

[Marek Vasut <marex@denx.de>]

On Sunday, April 13, 2014 at 09:55:57 PM, Ian Campbell wrote:
> On Mon, 2014-03-24 at 23:42 +0100, Olliver Schinagl wrote:
> > On 03/24/2014 09:52 PM, Marek Vasut wrote:
> > >> +	/* Switch to 24MHz clock while changing PLL1 */
> > >> +	writel(AXI_DIV_1 << AXI_DIV_SHIFT |
> > >> +	       AHB_DIV_2 << AHB_DIV_SHIFT |
> > >> +	       APB0_DIV_1 << APB0_DIV_SHIFT |
> > >> +	       CPU_CLK_SRC_OSC24M << CPU_CLK_SRC_SHIFT,
> > >> +	       &ccm->cpu_ahb_apb0_cfg);
> > >> +	sdelay(20);
> > > 
> > > What is sdelay() function all about ?
> > 
> > It also is from
> > arch/arm/include/asm/arch-sunxi/sys_proto.h
> > and I thought all where replaced with udelays
> 
> Since these sdelays() are used while we are frobbing around with the
> clocks I'm not sure that switching to udelay is possible/wise. sdelay is
> documented as:
>  * sdelay() - simple spin loop.  Will be constant time as
>  *  its generally used in bypass conditions only.  This
>  *  is necessary until timers are accessible.
> 
> IOW it sounds like it is designed to be used in exactly these
> circumstances.
> 
> Given the lack of documentation for what is actually required by the
> hardware when changing these clocks I'm a bit reluctant to go changing
> things.

Don't you have an clock-agnostic timer in the chip ? If not, well, can't be 
helped.

Best regards,
Marek Vasut