linux-kernel - [PATCH 1/3] mmc: sunxi: Disable HS-DDR mode for H5 eMMC controller by default

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Message-Id: <20190203155628.16767-2-wens@csie.org>
Date:   Sun,  3 Feb 2019 23:56:26 +0800
From:   Chen-Yu Tsai <wens@...e.org>
To:     Ulf Hansson <ulf.hansson@...aro.org>,
        Maxime Ripard <maxime.ripard@...tlin.com>
Cc:     Chen-Yu Tsai <wens@...e.org>, linux-mmc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-sunxi@...glegroups.com,
        Chris Blake <chrisrblake93@...il.com>, stable@...r.kernel.org
Subject: [PATCH 1/3] mmc: sunxi: Disable HS-DDR mode for H5 eMMC controller by default

Some H5 boards seem to not have proper trace lengths for eMMC to be able
to use the default setting for the delay chains under HS-DDR mode. These
include the Bananapi M2+ H5 and NanoPi NEO Core2. However the Libre
Computer ALL-H3-CC-H5 works just fine.

For the H5 (at least for now), default to not enabling HS-DDR modes in
the driver, and expect the device tree to signal HS-DDR capability on
boards that work.

Reported-by: Chris Blake <chrisrblake93@...il.com>
Fixes: 07bafc1e3536 ("mmc: sunxi: Use new timing mode for A64 eMMC controller")
Cc: <stable@...r.kernel.org>
Signed-off-by: Chen-Yu Tsai <wens@...e.org>
---
 drivers/mmc/host/sunxi-mmc.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/host/sunxi-mmc.c b/drivers/mmc/host/sunxi-mmc.c
index 279e326e397e..7415af8c8ff6 100644
--- a/drivers/mmc/host/sunxi-mmc.c
+++ b/drivers/mmc/host/sunxi-mmc.c
@@ -1399,7 +1399,16 @@ static int sunxi_mmc_probe(struct platform_device *pdev)
 	mmc->caps	       |= MMC_CAP_MMC_HIGHSPEED | MMC_CAP_SD_HIGHSPEED |
 				  MMC_CAP_ERASE | MMC_CAP_SDIO_IRQ;
 
-	if (host->cfg->clk_delays || host->use_new_timings)
+	/*
+	 * Some H5 devices do not have signal traces precise enough to
+	 * use HS DDR mode for their eMMC chips.
+	 *
+	 * We still enable HS DDR modes for all the other controller
+	 * variants that support them.
+	 */
+	if ((host->cfg->clk_delays || host->use_new_timings) &&
+	    !of_device_is_compatible(pdev->dev.of_node,
+				     "allwinner,sun50i-h5-emmc"))
 		mmc->caps      |= MMC_CAP_1_8V_DDR | MMC_CAP_3_3V_DDR;
 
 	ret = mmc_of_parse(mmc);
-- 
2.20.1