linux-kernel - [PATCH] mmc: sdhci-esdhc-imx: support eMMC DDR mode when running at 3.3V

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Message-Id: <20180628073136.21748-1-stefan@agner.ch>
Date:   Thu, 28 Jun 2018 09:31:36 +0200
From:   Stefan Agner <stefan@...er.ch>
To:     adrian.hunter@...el.com, ulf.hansson@...aro.org
Cc:     fabio.estevam@....com, haibo.chen@....com, aisheng.dong@....com,
        michael@...rulasolutions.com, linux-mmc@...r.kernel.org,
        linux-kernel@...r.kernel.org, Stefan Agner <stefan@...er.ch>
Subject: [PATCH] mmc: sdhci-esdhc-imx: support eMMC DDR mode when running at 3.3V

The uSDHC supports DDR modes for eMMC devices running at 3.3V. This
allows to run eMMC with 3.3V signaling voltage at DDR52 mode:

  # cat /sys/kernel/debug/mmc1/ios
  clock:          52000000 Hz
  vdd:            21 (3.3 ~ 3.4 V)
  bus mode:       2 (push-pull)
  chip select:    0 (don't care)
  power mode:     2 (on)
  bus width:      3 (8 bits)
  timing spec:    8 (mmc DDR52)
  signal voltage: 0 (3.30 V)
  driver type:    0 (driver type B)

Signed-off-by: Stefan Agner <stefan@...er.ch>
---
 drivers/mmc/host/sdhci-esdhc-imx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci-esdhc-imx.c
index b716b933f00a..6f444731754d 100644
--- a/drivers/mmc/host/sdhci-esdhc-imx.c
+++ b/drivers/mmc/host/sdhci-esdhc-imx.c
@@ -1324,7 +1324,7 @@ static int sdhci_esdhc_imx_probe(struct platform_device *pdev)
 
 	if (esdhc_is_usdhc(imx_data)) {
 		host->quirks2 |= SDHCI_QUIRK2_PRESET_VALUE_BROKEN;
-		host->mmc->caps |= MMC_CAP_1_8V_DDR;
+		host->mmc->caps |= MMC_CAP_1_8V_DDR | MMC_CAP_3_3V_DDR;
 		if (!(imx_data->socdata->flags & ESDHC_FLAG_HS200))
 			host->quirks2 |= SDHCI_QUIRK2_BROKEN_HS200;
 
-- 
2.18.0