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Message-ID: <CAPDyKFqMARrkX2R=f=dzAh9BjVHUgc9QQZpd1YVWX-Pz5C=Y9A@mail.gmail.com>
Date: Mon, 11 Jan 2021 19:06:31 +0100
From: Ulf Hansson <ulf.hansson@...aro.org>
To: Douglas Anderson <dianders@...omium.org>
Cc: Adrian Hunter <adrian.hunter@...el.com>,
Taniya Das <tdas@...eaurora.org>,
Veerabhadrarao Badiganti <vbadigan@...eaurora.org>,
Stephen Boyd <swboyd@...omium.org>,
Bjorn Andersson <bjorn.andersson@...aro.org>,
Andy Gross <agross@...nel.org>,
linux-arm-msm <linux-arm-msm@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>
Subject: Re: [PATCH v5 2/2] mmc: sdhci-msm: Actually set the actual clock
On Mon, 14 Dec 2020 at 18:23, Douglas Anderson <dianders@...omium.org> wrote:
>
> The MSM SDHCI driver always set the "actual_clock" field to 0. It had
> a comment about it not being needed because we weren't using the
> standard SDHCI divider mechanism and we'd just fallback to
> "host->clock". However, it's still better to provide the actual
> clock. Why?
>
> 1. It will make timeout calculations slightly better. On one system I
> have, the eMMC requets 200 MHz (for HS400-ES) but actually gets 192
> MHz. These are close, but why not get the more accurate one.
>
> 2. If things are seriously off in the clock driver and it's missing
> rates or picking the wrong rate (maybe it's rounding up instead of
> down), this will make it much more obvious what's going on.
>
> NOTE: we have to be a little careful here because the "actual_clock"
> field shouldn't include the multiplier that sdhci-msm needs
> internally.
>
> Suggested-by: Adrian Hunter <adrian.hunter@...el.com>
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> Reviewed-by: Bjorn Andersson <bjorn.andersson@...aro.org>
Applied for next, thanks!
Kind regards
Uffe
> ---
>
> Changes in v5:
> - Remove unused clock parameter.
> - Add a comment that we're stashing the requested rate.
>
> Changes in v4:
> - ("mmc: sdhci-msm: Actually set the actual clock") new for v4.
>
> drivers/mmc/host/sdhci-msm.c | 35 ++++++++++++++++-------------------
> 1 file changed, 16 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
> index 50beb407dbe9..f5669dc858d0 100644
> --- a/drivers/mmc/host/sdhci-msm.c
> +++ b/drivers/mmc/host/sdhci-msm.c
> @@ -328,8 +328,7 @@ static void sdhci_msm_v5_variant_writel_relaxed(u32 val,
> writel_relaxed(val, host->ioaddr + offset);
> }
>
> -static unsigned int msm_get_clock_rate_for_bus_mode(struct sdhci_host *host,
> - unsigned int clock)
> +static unsigned int msm_get_clock_mult_for_bus_mode(struct sdhci_host *host)
> {
> struct mmc_ios ios = host->mmc->ios;
> /*
> @@ -342,8 +341,8 @@ static unsigned int msm_get_clock_rate_for_bus_mode(struct sdhci_host *host,
> ios.timing == MMC_TIMING_MMC_DDR52 ||
> ios.timing == MMC_TIMING_MMC_HS400 ||
> host->flags & SDHCI_HS400_TUNING)
> - clock *= 2;
> - return clock;
> + return 2;
> + return 1;
> }
>
> static void msm_set_clock_rate_for_bus_mode(struct sdhci_host *host,
> @@ -354,14 +353,16 @@ static void msm_set_clock_rate_for_bus_mode(struct sdhci_host *host,
> struct mmc_ios curr_ios = host->mmc->ios;
> struct clk *core_clk = msm_host->bulk_clks[0].clk;
> unsigned long achieved_rate;
> + unsigned int desired_rate;
> + unsigned int mult;
> int rc;
>
> - clock = msm_get_clock_rate_for_bus_mode(host, clock);
> - rc = dev_pm_opp_set_rate(mmc_dev(host->mmc), clock);
> + mult = msm_get_clock_mult_for_bus_mode(host);
> + desired_rate = clock * mult;
> + rc = dev_pm_opp_set_rate(mmc_dev(host->mmc), desired_rate);
> if (rc) {
> pr_err("%s: Failed to set clock at rate %u at timing %d\n",
> - mmc_hostname(host->mmc), clock,
> - curr_ios.timing);
> + mmc_hostname(host->mmc), desired_rate, curr_ios.timing);
> return;
> }
>
> @@ -371,11 +372,14 @@ static void msm_set_clock_rate_for_bus_mode(struct sdhci_host *host,
> * encounter it.
> */
> achieved_rate = clk_get_rate(core_clk);
> - if (achieved_rate > clock)
> + if (achieved_rate > desired_rate)
> pr_warn("%s: Card appears overclocked; req %u Hz, actual %lu Hz\n",
> - mmc_hostname(host->mmc), clock, achieved_rate);
> + mmc_hostname(host->mmc), desired_rate, achieved_rate);
> + host->mmc->actual_clock = achieved_rate / mult;
> +
> + /* Stash the rate we requested to use in sdhci_msm_runtime_resume() */
> + msm_host->clk_rate = desired_rate;
>
> - msm_host->clk_rate = clock;
> pr_debug("%s: Setting clock at rate %lu at timing %d\n",
> mmc_hostname(host->mmc), achieved_rate, curr_ios.timing);
> }
> @@ -1756,13 +1760,6 @@ static unsigned int sdhci_msm_get_min_clock(struct sdhci_host *host)
> static void __sdhci_msm_set_clock(struct sdhci_host *host, unsigned int clock)
> {
> u16 clk;
> - /*
> - * Keep actual_clock as zero -
> - * - since there is no divider used so no need of having actual_clock.
> - * - MSM controller uses SDCLK for data timeout calculation. If
> - * actual_clock is zero, host->clock is taken for calculation.
> - */
> - host->mmc->actual_clock = 0;
>
> sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);
>
> @@ -1785,7 +1782,7 @@ static void sdhci_msm_set_clock(struct sdhci_host *host, unsigned int clock)
> struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
>
> if (!clock) {
> - msm_host->clk_rate = clock;
> + host->mmc->actual_clock = msm_host->clk_rate = 0;
> goto out;
> }
>
> --
> 2.29.2.576.ga3fc446d84-goog
>
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