linux-kernel - [PATCH 3.16 61/83] mmc: core: Fix init of SD cards reporting an invalid VDD range

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Date:   Wed, 20 Nov 2019 15:38:11 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Ulf Hansson" <ulf.hansson@...aro.org>,
        "Manuel Presnitz" <mail@....de>,
        "Philip Langdale" <philipl@...rt.org>
Subject: [PATCH 3.16 61/83] mmc: core: Fix init of SD cards reporting an
 invalid VDD range

3.16.78-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Ulf Hansson <ulf.hansson@...aro.org>

commit 72741084d903e65e121c27bd29494d941729d4a1 upstream.

The OCR register defines the supported range of VDD voltages for SD cards.
However, it has turned out that some SD cards reports an invalid voltage
range, for example having bit7 set.

When a host supports MMC_CAP2_FULL_PWR_CYCLE and some of the voltages from
the invalid VDD range, this triggers the core to run a power cycle of the
card to try to initialize it at the lowest common supported voltage.
Obviously this fails, since the card can't support it.

Let's fix this problem, by clearing invalid bits from the read OCR register
for SD cards, before proceeding with the VDD voltage negotiation.

Reported-by: Philip Langdale <philipl@...rt.org>
Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
Reviewed-by: Philip Langdale <philipl@...rt.org>
Tested-by: Philip Langdale <philipl@...rt.org>
Tested-by: Manuel Presnitz <mail@....de>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/mmc/core/sd.c | 6 ++++++
 1 file changed, 6 insertions(+)

--- a/drivers/mmc/core/sd.c
+++ b/drivers/mmc/core/sd.c
@@ -1242,6 +1242,12 @@ int mmc_attach_sd(struct mmc_host *host)
 			goto err;
 	}

+	/*
+	 * Some SD cards claims an out of spec VDD voltage range. Let's treat
+	 * these bits as being in-valid and especially also bit7.
+	 */
+	ocr &= ~0x7FFF;
+
 	rocr = mmc_select_voltage(host, ocr);

 	/*