[PATCH 1/8] clk: sunxi: factors: Add m_start parameters
wens at csie.org
Fri May 15 00:48:38 PDT 2015
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
> 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.
> Maxime Ripard, Free Electrons
> Embedded Linux, Kernel and Android engineering
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