linux-kernel - [PATCH 4.19 07/58] mmc: sdhci-xenon: fix 1.8v regulator stabilization

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Message-Id: <20210125183157.018313665@linuxfoundation.org>
Date:   Mon, 25 Jan 2021 19:39:08 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Alex Leibovich <alexl@...vell.com>,
        Marcin Wojtas <mw@...ihalf.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Ulf Hansson <ulf.hansson@...aro.org>
Subject: [PATCH 4.19 07/58] mmc: sdhci-xenon: fix 1.8v regulator stabilization

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

commit 1a3ed0dc3594d99ff341ec63865a40519ea24b8d upstream.

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 platforms 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
Acked-by: Adrian Hunter <adrian.hunter@...el.com>
Link: https://lore.kernel.org/r/20201211141656.24915-1-mw@semihalf.com
Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/mmc/host/sdhci-xenon.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

--- a/drivers/mmc/host/sdhci-xenon.c
+++ b/drivers/mmc/host/sdhci-xenon.c
@@ -170,7 +170,12 @@ static void xenon_reset_exit(struct sdhc
 	/* 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 possible 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);