[PATCH 1/8] clk: sunxi: factors: Add m_start parameters

[Chen-Yu Tsai]

On Fri, May 15, 2015 at 3:43 PM, Maxime Ripard
<maxime.ripard at free-electrons.com> wrote:
> On Thu, May 14, 2015 at 05:12:07PM +0800, Chen-Yu Tsai wrote:
>> On Sat, May 2, 2015 at 7:24 PM, Maxime Ripard
>> <maxime.ripard at free-electrons.com> wrote:
>> > Some clocks start incrementing the m factor at 0. Add a parameter to handle
>> > it just like we did for the N factor.
>> >
>> > Since the behaviour until now was to assume that the m factor was starting
>> > at 1, we also need to fix the other users.
>> >
>> > Signed-off-by: Maxime Ripard <maxime.ripard at free-electrons.com>
>> > ---
>> >  drivers/clk/sunxi/clk-factors.c    | 11 ++++++++++-
>> >  drivers/clk/sunxi/clk-factors.h    |  2 ++
>> >  drivers/clk/sunxi/clk-mod0.c       |  2 ++
>> >  drivers/clk/sunxi/clk-sun8i-mbus.c |  2 ++
>> >  drivers/clk/sunxi/clk-sun9i-core.c |  6 ++++++
>> >  drivers/clk/sunxi/clk-sunxi.c      | 10 ++++++++++
>> >  6 files changed, 32 insertions(+), 1 deletion(-)
>> >
>> > diff --git a/drivers/clk/sunxi/clk-factors.c b/drivers/clk/sunxi/clk-factors.c
>> > index 8c20190a3e9f..100a711c3e3d 100644
>> > --- a/drivers/clk/sunxi/clk-factors.c
>> > +++ b/drivers/clk/sunxi/clk-factors.c
>> > @@ -56,15 +56,24 @@ static unsigned long clk_factors_recalc_rate(struct clk_hw *hw,
>> >         /* Get each individual factor if applicable */
>> >         if (config->nwidth != SUNXI_FACTORS_NOT_APPLICABLE)
>> >                 n = FACTOR_GET(config->nshift, config->nwidth, reg);
>> > +
>> >         if (config->kwidth != SUNXI_FACTORS_NOT_APPLICABLE)
>> >                 k = FACTOR_GET(config->kshift, config->kwidth, reg);
>> > +
>> >         if (config->mwidth != SUNXI_FACTORS_NOT_APPLICABLE)
>> >                 m = FACTOR_GET(config->mshift, config->mwidth, reg);
>> > +       else
>> > +               /* Make sure we don't get a division by zero */
>> > +               m = 1;
>>
>> What happens when mwidth is valid, m_start = 0, and m = 0?
>
> That's a very good question. A division by zero in the kernel, I'd
> say.
>
> But I don't think we can end up in such a case today, and it's
> somewhat expected that it will happen, and no clock have looked at can
> actually end up in such a case.

It's possible if the bootloader left the clock in an invalid state.
How about just returning 0, indicating an invalid rate, early?

>> Other than that, this one looks good.
>
> Thanks!
>
> --
> Maxime Ripard, Free Electrons
> Embedded Linux, Kernel and Android engineering
> http://free-electrons.com