[PATCH 3.16.y-ckt 057/216] mmc: dw_mmc: avoid write to CDTHRCTL on older versions

[Luis Henriques]

3.16.7-ckt4 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: James Hogan <james.hogan at imgtec.com>

commit 66dfd10173159cafa9cb0d39936b8daeaab8e3e0 upstream.

Commit f1d2736c8156 (mmc: dw_mmc: control card read threshold) added
dw_mci_ctrl_rd_thld() with an unconditional write to the CDTHRCTL
register at offset 0x100. However before version 240a, the FIFO region
started at 0x100, so the write messes with the FIFO and completely
breaks the driver.

If the version id < 240A, return early from dw_mci_ctl_rd_thld() so as
not to hit this problem.

Fixes: f1d2736c8156 (mmc: dw_mmc: control card read threshold)
Signed-off-by: James Hogan <james.hogan at imgtec.com>
Acked-by: Jaehoon Chung <jh80.chung at samsung.com>
Signed-off-by: Ulf Hansson <ulf.hansson at linaro.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/mmc/host/dw_mmc.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
index 1ac227c603b7..609f0ab6891f 100644
--- a/drivers/mmc/host/dw_mmc.c
+++ b/drivers/mmc/host/dw_mmc.c
@@ -625,6 +625,13 @@ static void dw_mci_ctrl_rd_thld(struct dw_mci *host, struct mmc_data *data)
 
 	WARN_ON(!(data->flags & MMC_DATA_READ));
 
+	/*
+	 * CDTHRCTL doesn't exist prior to 240A (in fact that register offset is
+	 * in the FIFO region, so we really shouldn't access it).
+	 */
+	if (host->verid < DW_MMC_240A)
+		return;
+
 	if (host->timing != MMC_TIMING_MMC_HS200 &&
 	    host->timing != MMC_TIMING_UHS_SDR104)
 		goto disable;
-- 
2.1.4