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From: "Michał Mirosław" <mirq-linux@rere.qmqm.pl>
To: Adrian Hunter <adrian.hunter@intel.com>,
	Ulf Hansson <ulf.hansson@linaro.org>
Cc: linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v3] mmc: sdhci: fix minimum clock rate for v3 controller
Date: Wed, 15 Jan 2020 10:54:35 +0100	[thread overview]
Message-ID: <ffb489519a446caffe7a0a05c4b9372bd52397bb.1579082031.git.mirq-linux@rere.qmqm.pl> (raw)

For SDHCIv3+ with programmable clock mode, minimal clock frequency is
still base clock / max(divider). Minimal programmable clock frequency is
always greater than minimal divided clock frequency. Without this patch,
SDHCI uses out-of-spec initial frequency when multiplier is big enough:

mmc1: mmc_rescan_try_freq: trying to init card at 468750 Hz
[for 480 MHz source clock divided by 1024]

The code in sdhci_calc_clk() already chooses a correct SDCLK clock mode.

Cc: stable@vger.kernel.org
Fixes: c3ed3877625f ("mmc: sdhci: add support for programmable clock mode")
Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
---
 v3: commitmsg/comment rewording
 v2: extend commitmsg and add comment
---
 drivers/mmc/host/sdhci.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 96609c961465..24fb6d710de6 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -3903,11 +3903,13 @@ int sdhci_setup_host(struct sdhci_host *host)
 	if (host->ops->get_min_clock)
 		mmc->f_min = host->ops->get_min_clock(host);
 	else if (host->version >= SDHCI_SPEC_300) {
-		if (host->clk_mul) {
-			mmc->f_min = (host->max_clk * host->clk_mul) / 1024;
+		if (host->clk_mul)
 			max_clk = host->max_clk * host->clk_mul;
-		} else
-			mmc->f_min = host->max_clk / SDHCI_MAX_DIV_SPEC_300;
+		/*
+		 * Divided Clock Mode minimum clock rate is always less than
+		 * Programmable Clock Mode minimum clock rate.
+		 */
+		mmc->f_min = host->max_clk / SDHCI_MAX_DIV_SPEC_300;
 	} else
 		mmc->f_min = host->max_clk / SDHCI_MAX_DIV_SPEC_200;
 
-- 
2.20.1


             reply	other threads:[~2020-01-15  9:54 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-15  9:54 Michał Mirosław [this message]
2020-01-15 10:01 ` [PATCH v3] mmc: sdhci: fix minimum clock rate for v3 controller Adrian Hunter
2020-01-16 14:39 ` Ulf Hansson

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