linux-kernel - [PATCH 2/3] mmc: sunxi: Filter out unsupported modes declared in the device tree

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Message-Id: <20190203155628.16767-3-wens@csie.org>
Date:   Sun,  3 Feb 2019 23:56:27 +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 2/3] mmc: sunxi: Filter out unsupported modes declared in the device tree

The MMC device tree bindings include properties used to signal various
signalling speed modes. Until now the sunxi driver was accepting them
without any further filtering, while the sunxi device trees were not
actually using them.

Since some of the H5 boards can not run at higher speed modes stably,
we are resorting to declaring the higher speed modes per-board.

Regardless, having boards declare modes and blindly following them,
even without proper support in the driver, is generally a bad thing.

Filter out all unsupported modes from the capabilities mask after
the device tree properties have been parsed.

Cc: <stable@...r.kernel.org>
Signed-off-by: Chen-Yu Tsai <wens@...e.org>

---

This should be backported to stable kernels in case people try to run
new device trees (that declare newly supported modes) with old kernels.
---
 drivers/mmc/host/sunxi-mmc.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/mmc/host/sunxi-mmc.c b/drivers/mmc/host/sunxi-mmc.c
index 7415af8c8ff6..a01433012db0 100644
--- a/drivers/mmc/host/sunxi-mmc.c
+++ b/drivers/mmc/host/sunxi-mmc.c
@@ -1415,6 +1415,22 @@ static int sunxi_mmc_probe(struct platform_device *pdev)
 	if (ret)
 		goto error_free_dma;
 
+	/*
+	 * If we don't support delay chains in the SoC, we can't use any
+	 * of the DDR speed modes. Mask them out in case the device
+	 * tree specifies the properties for them, which gets added to
+	 * the caps by mmc_of_parse() above.
+	 */
+	if (!(host->cfg->clk_delays || host->use_new_timings))
+		mmc->caps &= ~(MMC_CAP_3_3V_DDR | MMC_CAP_1_8V_DDR |
+			       MMC_CAP_1_2V_DDR);
+
+	/* TODO: UHS modes untested due to lack of supporting boards */
+	mmc->caps &= ~MMC_CAP_UHS;
+
+	/* TODO: This driver doesn't support HS200 and HS400 modes yet */
+	mmc->caps2 &= ~(MMC_CAP2_HS200 | MMC_CAP2_HS400);
+
 	ret = sunxi_mmc_init_host(host);
 	if (ret)
 		goto error_free_dma;
-- 
2.20.1