Hi Heiko,
On Tue, 2015-07-07 at 11:34 +0200, Heiko Stübner wrote:
> > > > @@ -135,16 +138,26 @@ static void mtk_pll_calc_values(struct mtk_clk_pll
> > > > *pll, u32 *pcw, u32 *postdiv, u32 freq, u32 fin)
> > > >
> > > > {
> > > >
> > > > unsigned long fmin = 1000 * MHZ;
> > > >
> > > > + const unsigned long *div_rate = pll->data->div_rate;
> > > >
> > > > u64 _pcw;
> > > > u32 val;
> > > >
> > > > if (freq > pll->data->fmax)
> > > >
> > > > freq = pll->data->fmax;
> > > >
> > > > - for (val = 0; val < 4; val++) {
> > > > + if (div_rate) {
> > > > + for (val = 1; div_rate[val] != 0; val++) {
> > > > + if (freq > div_rate[val])
> > > > + break;
> > > > + }
> > > > + val--;
> > >
> > > if you're changing the table struct, this of course also would need to be
> > > adapted.
> > >
> > >
> > > Hmm, what I don't understand is, what does MT8173_PLL_FMAX in the table,
> > > if
> > > you ignore it here all the time?
> > >
> > > So the table should probably look more like [when using the concept from
> > > above]
> > >
> > > static const struct mtk_pll_div_table mmpll_div_rate[] = {
> > >
> > > { .freq = 1000000000, .div = 0 },
> > > { .freq = 702000000, .div = 1 },
> > > { .freq = 253500000, .div = 2 },
> > > { .freq = 126750000, .div = 3 },
> > > { /* sentinel */ },
> > >
> > > };
> >
> > The freq-div table describes the maximum frequency of each divider
> > setting. Although the first element doesn't used in current
> > implementation, I think it's better to keep freq-div table's
> > completeness.
>
> the issue I see is, that its value is currently 0 and the code substracts 1.
> So if anything would (accidentially) select MT8173_PLL_FMAX, the u32 val would
> wrap around, as you're subtracting 1 from 0 .
Subtracting 1 from val is safe now because it starts from 1:
for (val = 1; div_rate[val] != 0; val++) {
...
}
val--;
I can change this implementation to a more readable one such as:
for (val = 0; div_rate[val + 1] != 0; val++) {
if (freq <= div_rate[val] && freq > div_rate[val + 1]) {
...
Do you think it is OK?
Best regards,
James
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