mmc: at91_mci: Enable MMC_CAP_SDIO_IRQ only when it actually works.

According to the datasheets AT91SAM9261 does not support SDIO interrupts,
and AT91SAM9260/9263 have an erratum requiring 4bit mode while using slot
B for the interrupt to work.
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Wolfgang Muees <wolfgang.mues@auerswald.de>
Cc: Andrew Victor <avictor.za@gmail.com>
Cc: <linux-mmc@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/mmc/host/at91_mci.c

@@ -929,7 +929,7 @@ static int __init at91_mci_probe(struct platform_device *pdev)
 	mmc->f_min = 375000;
 	mmc->f_max = 25000000;
 	mmc->ocr_avail = MMC_VDD_32_33 | MMC_VDD_33_34;
-	mmc->caps = MMC_CAP_SDIO_IRQ;
+	mmc->caps = 0;
 
 	mmc->max_blk_size  = MCI_MAXBLKSIZE;
 	mmc->max_blk_count = MCI_BLKATONCE;
@@ -958,6 +958,13 @@ static int __init at91_mci_probe(struct platform_device *pdev)
 		goto fail5;
 	}
 
+	/* Add SDIO capability when available */
+	if (cpu_is_at91sam9260() || cpu_is_at91sam9263()) {
+		/* AT91SAM9260/9263 erratum */
+		if (host->board->wire4 || !host->board->slot_b)
+			mmc->caps |= MMC_CAP_SDIO_IRQ;
+	}
+
 	/*
 	 * Reserve GPIOs ... board init code makes sure these pins are set
 	 * up as GPIOs with the right direction (input, except for vcc)