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From: Zhoujie Wu <zjwu@marvell.com>
To: ulf.hansson@linaro.org, adrian.hunter@intel.com,
	linux-mmc@vger.kernel.org
Cc: zmxu@marvell.com, jszhang@marvell.com, nadavh@marvell.com,
	xigu@marvell.com, xswang@marvell.com, dingwei@marvell.com,
	kostap@marvell.com, hannah@marvell.com, hongd@marvell.com,
	dougj@marvell.com, ygao@marvell.com, liuw@marvell.com,
	gregory.clement@free-electrons.com,
	thomas.petazzoni@free-electrons.com,
	Zhoujie Wu <zjwu@marvell.com>
Subject: [PATCH] mmc: sdhci: wait 5ms after set 1.8V signal enable
Date: Wed, 13 Dec 2017 15:41:30 -0800	[thread overview]
Message-ID: <1513208490-13278-1-git-send-email-zjwu@marvell.com> (raw)

According to SD spec 3.00 3.6.1 signal voltage switch
procedure, host should wait 5ms after set 1.8V signal
enable bit in Host Control 2 register and check if 1.8V
is stable or not.

On some cards, found without the delay would see "1.8V
regulator output did not became stable" err log.

Signed-off-by: Zhoujie Wu <zjwu@marvell.com>
---
 drivers/mmc/host/sdhci.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index e9290a3..fe5f208 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -1933,6 +1933,9 @@ int sdhci_start_signal_voltage_switch(struct mmc_host *mmc,
 		if (host->ops->voltage_switch)
 			host->ops->voltage_switch(host);
 
+		/* Wait for 5ms */
+		usleep_range(5000, 5500);
+
 		/* 1.8V regulator output should be stable within 5 ms */
 		ctrl = sdhci_readw(host, SDHCI_HOST_CONTROL2);
 		if (ctrl & SDHCI_CTRL_VDD_180)
-- 
1.9.1


                 reply	other threads:[~2017-12-13 23:41 UTC|newest]

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