linux-kernel - [PATCH v4 1/5] mmc: sdhci: fix base clock usage in preset value

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Message-Id: <fff139f001835efb5ee428093a9522d7761642de.1627204633.git.mirq-linux@rere.qmqm.pl>
Date:   Sun, 25 Jul 2021 11:20:47 +0200
From:   Michał Mirosław <mirq-linux@...e.qmqm.pl>
To:     Ulf Hansson <ulf.hansson@...aro.org>,
        Kevin Liu <kliu5@...vell.com>,
        Michal Simek <michal.simek@...inx.com>,
        Suneel Garapati <suneel.garapati@...inx.com>
Cc:     Adrian Hunter <adrian.hunter@...el.com>, linux-mmc@...r.kernel.org,
        linux-kernel@...r.kernel.org, Al Cooper <alcooperx@...il.com>
Subject: [PATCH v4 1/5] mmc: sdhci: fix base clock usage in preset value

Fixed commit added an unnecessary read of CLOCK_CONTROL. The value read
is overwritten for programmable clock preset, but is carried over for
divided clock preset. This can confuse sdhci_enable_clk() if the register
has enable bits set for some reason at time time of clock calculation.
Remove the read.

Quoting Al Cooper:

sdhci_brcmstb_set_clock() assumed that sdhci_calc_clk() would always
return the divider value without the enable set, so this fixes a case
for DDR52 where the enable was not being cleared when the divider
value was changed.

Cc: stable@...r.kernel.org
Fixes: 52983382c74f ("mmc: sdhci: enhance preset value function")
Signed-off-by: Michał Mirosław <mirq-linux@...e.qmqm.pl>
Acked-by: Al Cooper <alcooperx@...il.com>

---
v4: no changes
v3: updated commit message
v2: removed truncated sentence from commitmsg

Signed-off-by: Michał Mirosław <mirq-linux@...e.qmqm.pl>
---
 drivers/mmc/host/sdhci.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index aba6e10b8605..c7438dd13e3e 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -1857,7 +1857,6 @@ u16 sdhci_calc_clk(struct sdhci_host *host, unsigned int clock,
 		if (host->preset_enabled) {
 			u16 pre_val;
 
-			clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
 			pre_val = sdhci_get_preset_value(host);
 			div = FIELD_GET(SDHCI_PRESET_SDCLK_FREQ_MASK, pre_val);
 			if (host->clk_mul &&
-- 
2.30.2