On Thu, Sep 26, 2013 at 10:24:04AM +0200, Andrew Lunn wrote:
> Hi Ezequiel
>
> > +static int clk_corediv_enable(struct clk_hw *hwclk)
> > +{
> > + struct clk_corediv *corediv = to_corediv_clk(hwclk);
> > + struct clk_corediv_desc *desc = &corediv->desc;
> > + u32 reg;
> > +
> > + reg = readl(corediv->reg);
> > + reg |= (BIT(desc->fieldbit) << CORE_CLOCK_DIVIDER_ENABLE_OFFSET);
> > + writel(reg, corediv->reg);
> > + return 0;
> > +}
>
> Shouldn't there be spinlocks around these register accesses? At least
> the core gate clk driver has a spinlock.
>
Indeed.
> > +static long clk_corediv_round_rate(struct clk_hw *hwclk, unsigned long rate,
> > + unsigned long *parent_rate)
> > +{
> > + /* Valid ratio are 1:4, 1:5, 1:6 and 1:8 */
> > + u32 div;
> > +
> > + div = *parent_rate / rate;
> > + if (div <= 4)
> > + div = 4;
> > + else if (div <= 5)
> > + div = 5;
> > + else if (div <= 6)
> > + div = 6;
> > + else
> > + div = 8;
> > +
> > + return *parent_rate / div;
> > +}
>
> This looks odd. Is not the following clearer?
>
> div = *parent_rate / rate;
> if (div < 5)
> div = 4;
> else if (div > 6)
> div = 8;
>
> The CodingStyle might require some {} here?
>
Mmmm... no, it's not at all clearer to me.
IMHO, the original construction explicitly show the possible ratios:
/* If it's smaller than or equal to 4, set to 4 */
if (div <= 4)
div = 4;
/* Otherwise, if it's between 4 and 5, set to 5 */
else if (div <= 5)
div = 5;
/* Otherwise, if it's between 5 and 6, set to 6 */
else if (div <= 6)
div = 6;
/* Otherwise, if it's bigger than 6, set to 8 */
else
div = 8;
(And I don't think we need any braces).
Is this not clear?
> + /*
> + * Wait for clocks to settle down, and then clear all the
> + * ratios request and the reload request.
> + */
> + udelay(1000);
> + reg &= ~(CORE_CLOCK_DIVIDER_RATIO_MASK | CORE_CLOCK_DIVIDER_RATIO_RELOAD);
> + writel(reg, corediv->reg);
> + udelay(1000);
>
>
> Documentation/timers/timers-howto.txt says:
>
> SLEEPING FOR ~USECS OR SMALL MSECS ( 10us - 20ms):
> * Use usleep_range
>
Right, forgot about that as well...
Thanks for the feedback!
--
Ezequiel García, Free Electrons
Embedded Linux, Kernel and Android Engineering
http://free-electrons.com
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