On Wed, Aug 04, 2021 at 01:52:21PM +0300, Adrian Hunter wrote:
> On 25/07/21 12:20 pm, Michał Mirosław wrote:
> > When host controller uses programmable clock presets but doesn't
> > advertise programmable clock support, we can only guess what frequency
> > it generates. Let's at least return correct SDHCI_PROG_CLOCK_MODE bit
> > value in this case.
> If the preset value doesn't make sense, why use it at all?
If I understand the spec correctly, when the preset value is used the
values in Clock Control register are ignored by the module and so the
module can also actually use a different clock source than the ones
available to the driver directly. So either way the driver can't be
sure of the exact frequencu used. This is a cleanup to remove a case
when the code ignores a bit's value based on other unspecified assumptions.
[...]
> > --- a/drivers/mmc/host/sdhci.c
> > +++ b/drivers/mmc/host/sdhci.c
> > @@ -1859,11 +1859,14 @@ u16 sdhci_calc_clk(struct sdhci_host *host, unsigned int clock,
> >
> > pre_val = sdhci_get_preset_value(host);
> > div = FIELD_GET(SDHCI_PRESET_SDCLK_FREQ_MASK, pre_val);
> > - if (host->clk_mul &&
> > - (pre_val & SDHCI_PRESET_CLKGEN_SEL)) {
> > + if (pre_val & SDHCI_PRESET_CLKGEN_SEL) {
> > clk = SDHCI_PROG_CLOCK_MODE;
> > real_div = div + 1;
> > clk_mul = host->clk_mul;
> > + if (!clk_mul) {
> > + /* The clock frequency is unknown. Assume undivided base. */
> > + clk_mul = 1;
> > + }
> > } else {
> > real_div = max_t(int, 1, div << 1);
> > }
