[PATCH v3 1/13] mmc: sunxi: Fix clock frequency change sequence

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 




The MMC and SD specifications documents that the clock frequency should
only be changed once gated.

The current code first modifies the parent clock, gates it and then
modifies the internal divider. This means that since the parent clock rate
might be changed, the bus clock might be changed as well before it is
gated, which breaks the specification.

Move the gating before the parent rate modification.

Signed-off-by: Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx>
---
 drivers/mmc/host/sunxi-mmc.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/mmc/host/sunxi-mmc.c b/drivers/mmc/host/sunxi-mmc.c
index b1d1303389a7..ab4324e6eb74 100644
--- a/drivers/mmc/host/sunxi-mmc.c
+++ b/drivers/mmc/host/sunxi-mmc.c
@@ -761,6 +761,10 @@ static int sunxi_mmc_clk_set_rate(struct sunxi_mmc_host *host,
 	u32 rval, clock = ios->clock;
 	int ret;
 
+	ret = sunxi_mmc_oclk_onoff(host, 0);
+	if (ret)
+		return ret;
+
 	/* 8 bit DDR requires a higher module clock */
 	if (ios->timing == MMC_TIMING_MMC_DDR52 &&
 	    ios->bus_width == MMC_BUS_WIDTH_8)
@@ -783,10 +787,6 @@ static int sunxi_mmc_clk_set_rate(struct sunxi_mmc_host *host,
 		return ret;
 	}
 
-	ret = sunxi_mmc_oclk_onoff(host, 0);
-	if (ret)
-		return ret;
-
 	/* clear internal divider */
 	rval = mmc_readl(host, REG_CLKCR);
 	rval &= ~0xff;
-- 
git-series 0.8.11
--
To unsubscribe from this list: send the line "unsubscribe devicetree" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html



[Index of Archives]     [Device Tree Compilter]     [Device Tree Spec]     [Linux Driver Backports]     [Video for Linux]     [Linux USB Devel]     [Linux PCI Devel]     [Linux Audio Users]     [Linux Kernel]     [Linux SCSI]     [XFree86]     [Yosemite Backpacking]
  Powered by Linux