On Thu, 2 Jan 2020 at 11:54, Michał Mirosław <mirq-linux@xxxxxxxxxxxx> wrote:
>
> Currently MMC core disregards host->f_max during card initialization
> phase. Obey upper boundary for the clock frequency and skip faster
> speeds when they are above the limit.
Is this a hypothetical problem or a real problem?
>
> Signed-off-by: Michał Mirosław <mirq-linux@xxxxxxxxxxxx>
> ---
> drivers/mmc/core/core.c | 10 ++++++++--
> 1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index abf8f5eb0a1c..aa54d359dab7 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -2330,7 +2330,13 @@ void mmc_rescan(struct work_struct *work)
> }
>
> for (i = 0; i < ARRAY_SIZE(freqs); i++) {
> - if (!mmc_rescan_try_freq(host, max(freqs[i], host->f_min)))
> + unsigned int freq = freqs[i];
> + if (freq > host->f_max) {
> + if (i + 1 < ARRAY_SIZE(freqs))
> + continue;
> + freq = host->f_max;
This looks wrong to me. For example, what if f_max = 250KHz and f_min = 50 KHz.
Then we should try with 250KHz, then 200KHz and then 100KHz. This
isn't what the above code does, I think.
Instead it will try with 200KHz and then 100KHz, thus skip 250KHz.
Maybe we should figure out what index of freqs[] to start the loop for
(before actually starting the loop), depending on the value of f_max -
rather than always start at 0.
> + }
> + if (!mmc_rescan_try_freq(host, max(freq, host->f_min)))
> break;
> if (freqs[i] <= host->f_min)
> break;
> @@ -2344,7 +2350,7 @@ void mmc_rescan(struct work_struct *work)
>
> void mmc_start_host(struct mmc_host *host)
> {
> - host->f_init = max(freqs[0], host->f_min);
> + host->f_init = max(min(freqs[0], host->f_max), host->f_min);
> host->rescan_disable = 0;
> host->ios.power_mode = MMC_POWER_UNDEFINED;
>
> --
> 2.20.1
>
Kind regards
Uffe
