linux-kernel - [PATCH v2] mmc: host: Wait for Vdd to settle on card power off

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Message-ID: <20250314195021.1588090-1-erick.shepherd@ni.com>
Date: Fri, 14 Mar 2025 14:50:21 -0500
From: Erick Shepherd <erick.shepherd@...com>
To: <linux-mmc@...r.kernel.org>
CC: <ulf.hansson@...aro.org>, <adrian.hunter@...el.com>,
        <linux-kernel@...r.kernel.org>, Erick Shepherd <erick.shepherd@...com>
Subject: [PATCH v2] mmc: host: Wait for Vdd to settle on card power off

The SD spec version 6.0 section 6.4.1.5 requires that Vdd must be
lowered to less than 0.5V for a minimum of 1 ms when powering off a
card. Increase wait to 15 ms so that voltage has time to drain down
to 0.5V and cards can power off correctly. Issues with voltage drain
time were only observed on Apollo Lake and Bay Trail host controllers
so this fix is limited to those devices.

Signed-off-by: Erick Shepherd <erick.shepherd@...com>
---
 drivers/mmc/host/sdhci-pci-core.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/mmc/host/sdhci-pci-core.c b/drivers/mmc/host/sdhci-pci-core.c
index 1f0bd723f011..b1f7c11ea61e 100644
--- a/drivers/mmc/host/sdhci-pci-core.c
+++ b/drivers/mmc/host/sdhci-pci-core.c
@@ -610,9 +610,12 @@ static void sdhci_intel_set_power(struct sdhci_host *host, unsigned char mode,
 
 	sdhci_set_power(host, mode, vdd);
 
-	if (mode == MMC_POWER_OFF)
+	if (mode == MMC_POWER_OFF) {
+		if (slot->chip->pdev->device == PCI_DEVICE_ID_INTEL_APL_SD ||
+		    slot->chip->pdev->device == PCI_DEVICE_ID_INTEL_BYT_SD)
+			usleep_range(15000, 17500);
 		return;
-
+	}
 	/*
 	 * Bus power might not enable after D3 -> D0 transition due to the
 	 * present state not yet having propagated. Retry for up to 2ms.
-- 
2.43.0