linux-kernel - [PATCH 4.2.y-ckt 046/268] mmc: sdhci-pci: Do not default to 33 Ohm driver strength for Intel SPT

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Message-Id: <1453926929-17663-47-git-send-email-kamal@canonical.com>
Date:	Wed, 27 Jan 2016 12:31:47 -0800
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Adrian Hunter <adrian.hunter@...el.com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 4.2.y-ckt 046/268] mmc: sdhci-pci: Do not default to 33 Ohm driver strength for Intel SPT

4.2.8-ckt3 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Adrian Hunter <adrian.hunter@...el.com>

commit 1ca896856281d3f1ad4f6f7d4e32e2943452de23 upstream.

In some cases, the stronger 33 Ohm driver strength must not be used
so it is not a suitable default.  Change it to the standard default
50 Ohm value.

The patch applies to v4.2+ except the file name changed.  It is
drivers/mmc/host/sdhci-pci.c prior to v.4.4.

Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 drivers/mmc/host/sdhci-pci.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mmc/host/sdhci-pci.c b/drivers/mmc/host/sdhci-pci.c
index b3b0a3e..5d2e222 100644
--- a/drivers/mmc/host/sdhci-pci.c
+++ b/drivers/mmc/host/sdhci-pci.c
@@ -277,7 +277,7 @@ static int spt_select_drive_strength(struct sdhci_host *host,
 	if (sdhci_pci_spt_drive_strength > 0)
 		drive_strength = sdhci_pci_spt_drive_strength & 0xf;
 	else
-		drive_strength = 1; /* 33-ohm */
+		drive_strength = 0; /* Default 50-ohm */
 
 	if ((mmc_driver_type_mask(drive_strength) & card_drv) == 0)
 		drive_strength = 0; /* Default 50-ohm */
-- 
1.9.1