linux-kernel - [PATCH] mmc: sdhci-xenon: fix 1.8v regulator stabilization

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Date:   Fri, 11 Dec 2020 15:16:56 +0100
From:   Marcin Wojtas <mw@...ihalf.com>
To:     linux-kernel@...r.kernel.org, linux-mmc@...r.kernel.org
Cc:     ulf.hansson@...aro.org, huziji@...vell.com,
        adrian.hunter@...el.com, jaz@...ihalf.com, tn@...ihalf.com,
        kostap@...vell.com, Alex Leibovich <alexl@...vell.com>,
        Marcin Wojtas <mw@...ihalf.com>, stable@...r.kernel.org
Subject: [PATCH] mmc: sdhci-xenon: fix 1.8v regulator stabilization

From: Alex Leibovich <alexl@...vell.com>

Automatic Clock Gating is a feature used for the power
consumption optimisation. It turned out that
during early init phase it may prevent the stable voltage
switch to 1.8V - due to that on some platfroms an endless
printout in dmesg can be observed:
"mmc1: 1.8V regulator output did not became stable"
Fix the problem by disabling the ACG at very beginning
of the sdhci_init and let that be enabled later.

Fixes: 3a3748dba881 ("mmc: sdhci-xenon: Add Marvell Xenon SDHC core functionality")
Signed-off-by: Alex Leibovich <alexl@...vell.com>
Signed-off-by: Marcin Wojtas <mw@...ihalf.com>
Cc: stable@...r.kernel.org
---
 drivers/mmc/host/sdhci-xenon.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/host/sdhci-xenon.c b/drivers/mmc/host/sdhci-xenon.c
index c67611fdaa8a..4b05f6fdefb4 100644
--- a/drivers/mmc/host/sdhci-xenon.c
+++ b/drivers/mmc/host/sdhci-xenon.c
@@ -168,7 +168,12 @@ static void xenon_reset_exit(struct sdhci_host *host,
 	/* Disable tuning request and auto-retuning again */
 	xenon_retune_setup(host);
 
-	xenon_set_acg(host, true);
+	/*
+	 * The ACG should be turned off at the early init time, in order
+	 * to solve a possile issues with the 1.8V regulator stabilization.
+	 * The feature is enabled in later stage.
+	 */
+	xenon_set_acg(host, false);
 
 	xenon_set_sdclk_off_idle(host, sdhc_id, false);
 
-- 
2.29.0