linux-kernel - [PATCH v3 1/2] mmc: sdhci-iproc: cygnus: Set NO_HISPD bit to fix HS50 data hold time problem

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Message-Id: <20190509172427.17835-2-scott.branden@broadcom.com>
Date:   Thu,  9 May 2019 10:24:26 -0700
From:   Scott Branden <scott.branden@...adcom.com>
To:     Adrian Hunter <adrian.hunter@...el.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Ray Jui <rjui@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>,
        Stefan Wahren <stefan.wahren@...e.com>
Cc:     BCM Kernel Feedback <bcm-kernel-feedback-list@...adcom.com>,
        linux-mmc@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Trac Hoang <trac.hoang@...adcom.com>,
        stable@...r.kernel.org, Scott Branden <scott.branden@...adcom.com>
Subject: [PATCH v3 1/2] mmc: sdhci-iproc: cygnus: Set NO_HISPD bit to fix HS50 data hold time problem

From: Trac Hoang <trac.hoang@...adcom.com>

The iproc host eMMC/SD controller hold time does not meet the
specification in the HS50 mode. This problem can be mitigated
by disabling the HISPD bit; thus forcing the controller output
data to be driven on the falling clock edges rather than the
rising clock edges.

This change applies only to the Cygnus platform.

Stable tag (v4.12+) chosen to assist stable kernel maintainers so that
the change does not produce merge conflicts backporting to older kernel
versions. In reality, the timing bug existed since the driver was first
introduced but there is no need for this driver to be supported in kernel
versions that old.

Cc: stable@...r.kernel.org # v4.12+
Signed-off-by: Trac Hoang <trac.hoang@...adcom.com>
Signed-off-by: Scott Branden <scott.branden@...adcom.com>
Acked-by: Adrian Hunter <adrian.hunter@...el.com>
---
 drivers/mmc/host/sdhci-iproc.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/host/sdhci-iproc.c b/drivers/mmc/host/sdhci-iproc.c
index 9d12c06c7fd6..9d4071c41c94 100644
--- a/drivers/mmc/host/sdhci-iproc.c
+++ b/drivers/mmc/host/sdhci-iproc.c
@@ -196,7 +196,8 @@ static const struct sdhci_ops sdhci_iproc_32only_ops = {
 };
 
 static const struct sdhci_pltfm_data sdhci_iproc_cygnus_pltfm_data = {
-	.quirks = SDHCI_QUIRK_DATA_TIMEOUT_USES_SDCLK,
+	.quirks = SDHCI_QUIRK_DATA_TIMEOUT_USES_SDCLK |
+		  SDHCI_QUIRK_NO_HISPD_BIT,
 	.quirks2 = SDHCI_QUIRK2_ACMD23_BROKEN | SDHCI_QUIRK2_HOST_OFF_CARD_ON,
 	.ops = &sdhci_iproc_32only_ops,
 };
-- 
2.17.1