sdhci-of: avoid writing reserved bits into host control register

SDHCI core tries to write HISPD bit into the host control register, but
the eSDHC controllers don't have that bit, and that causes all sorts of
misbehaviour when using 4-bit mode capable SD cards.
Signed-off-by: NAnton Vorontsov <avorontsov@ru.mvista.com>
Cc: Pierre Ossman <pierre@ossman.eu>
Cc: Kumar Gala <galak@kernel.crashing.org>
Cc: David Vrabel <david.vrabel@csr.com>
Cc: Ben Dooks <ben@fluff.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: <linux-mmc@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/mmc/host/sdhci-of.c

@@ -48,6 +48,8 @@ struct sdhci_of_host {
 #define ESDHC_CLOCK_HCKEN	0x00000002
 #define ESDHC_CLOCK_IPGEN	0x00000001
 
+#define ESDHC_HOST_CONTROL_RES	0x05
+
 static u32 esdhc_readl(struct sdhci_host *host, int reg)
 {
 	return in_be32(host->ioaddr + reg);
@@ -109,6 +111,10 @@ static void esdhc_writeb(struct sdhci_host *host, u8 val, int reg)
 	int base = reg & ~0x3;
 	int shift = (reg & 0x3) * 8;
 
+	/* Prevent SDHCI core from writing reserved bits (e.g. HISPD). */
+	if (reg == SDHCI_HOST_CONTROL)
+		val &= ~ESDHC_HOST_CONTROL_RES;
+
 	clrsetbits_be32(host->ioaddr + base , 0xff << shift, val << shift);
 }