linux-kernel - [PATCH v4 2/2] mmc: sdhci-msm: Actually set the actual clock

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Date:   Fri, 11 Dec 2020 09:12:33 -0800
From:   Douglas Anderson <dianders@...omium.org>
To:     Ulf Hansson <ulf.hansson@...aro.org>,
        Adrian Hunter <adrian.hunter@...el.com>
Cc:     Stephen Boyd <swboyd@...omium.org>,
        Taniya Das <tdas@...eaurora.org>, vbadigan@...eaurora.org,
        Douglas Anderson <dianders@...omium.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mmc@...r.kernel.org
Subject: [PATCH v4 2/2] mmc: sdhci-msm: Actually set the actual clock

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.

Signed-off-by: Douglas Anderson <dianders@...omium.org>
---

Changes in v4:
- ("mmc: sdhci-msm: Actually set the actual clock") new for v4.

 drivers/mmc/host/sdhci-msm.c | 32 ++++++++++++++------------------
 1 file changed, 14 insertions(+), 18 deletions(-)

diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
index 50beb407dbe9..08a3960001ad 100644
--- a/drivers/mmc/host/sdhci-msm.c
+++ b/drivers/mmc/host/sdhci-msm.c
@@ -328,7 +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,
+static unsigned int msm_get_clock_mult_for_bus_mode(struct sdhci_host *host,
 						    unsigned int clock)
 {
 	struct mmc_ios ios = host->mmc->ios;
@@ -342,8 +342,8 @@ 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 +354,16 @@ 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, clock);
+	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 +373,12 @@ 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;
 
-	msm_host->clk_rate = clock;
+	msm_host->clk_rate = desired_rate;
 	pr_debug("%s: Setting clock at rate %lu at timing %d\n",
 		 mmc_hostname(host->mmc), achieved_rate, curr_ios.timing);
 }
@@ -1756,13 +1759,6 @@ 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 +1781,7 @@ 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