linux-kernel - Re: [PATCH E 11/14] OMAP clock: track child clocks

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Date:	Sun, 22 Feb 2009 16:37:31 -0700 (MST)
From:	Paul Walmsley <paul@...an.com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
cc:	linux-arm-kernel@...ts.arm.linux.org.uk,
	linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org,
	r-woodruff2@...com, Tony Lindgren <tony@...mide.com>
Subject: Re: [PATCH E 11/14] OMAP clock: track child clocks

Hello Russell,

On Sat, 14 Feb 2009, Russell King - ARM Linux wrote:

> However, looking a little deeper, there's more issues in the reparenting
> area.  I don't think this code has been tested at all...  In
> _omap2_clksel_get_src_field, there is this:
> 
> 	for (clkr = clks->rates; clkr->div; clkr++) {
> 		if (clkr->flags & (cpu_mask | DEFAULT_RATE))
> 			break; /* Found the default rate for this platform */
> 	}
> 
> which is bogus - it will find the first entry which is _either_ marked
> as a default rate _or_ is supported by the SoC.  This means (for
> instance) that:
> 
> static const struct clksel_rate core_l3_core_rates[] = {
>         { .div = 1, .val = 1, .flags = RATE_IN_24XX },
>         { .div = 2, .val = 2, .flags = RATE_IN_242X },
>         { .div = 4, .val = 4, .flags = RATE_IN_24XX | DEFAULT_RATE },
> 
> will give us divisor 1 rather than presumably the one we want, that being
> divisor 4.  I think the test above should be:
> 
> 	for (clkr = clks->rates; clkr->div; clkr++) {
> 		if (clkr->flags & cpu_mask &&
> 		    clkr->flags & DEFAULT_RATE)
> 			break; /* Found the default rate for this platform */
> 	}
> 
> so we find an entry which is supported _and_ is the default for the SoC.

Agreed.

> There's also a second issue - the comments before omap2_divisor_to_clksel()
> indicate that this function returns 0xffffffff on error.  Unfortunately,
> this is not so, it actually returns zero on error.  Moreover, we test
> the result of the function against ~0, so we'll never deal with the error
> case.  This really should be fixed so that we return the right value for
> the error case.  (Further comments on this in a follow up.)

Agreed here also.

> So, below is a patch which fixes both of these issues.

Looks good, thanks Russell.

Acked-by: Paul Walmsley <paul@...an.com>


- Paul
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