mmc: dw_mmc: don't hard code fifo depth, fix usage

The FIFO_DEPTH hardware configuration parameter can be found from the
power-on value of RX_WMark in the FIFOTH register. This is used to
initialise the watermarks, but when calculating the number of free fifo
spaces a preprocessor definition is used which is hard coded to 32.

Fix reading the value out of FIFOTH (the default value in the RX_WMark
field is FIFO_DEPTH-1 not FIFO_DEPTH). Allow the fifo depth to be
overriden by platform data (since a bootloader may have changed FIFOTH
making auto-detection unreliable). Store the fifo_depth for later use.
Also fix the calculation to find the number of free bytes in the fifo to
include the fifo depth in the left shift by the data shift, since the
fifo depth is measured in fifo items not bytes.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Acked-by: Will Newton <will.newton@imgtec.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

2 files changed, 18 insertions, 6 deletions

diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
index 3f610d55f38e..3832312ce7cb 100644
--- a/drivers/mmc/host/dw_mmc.c
+++ b/drivers/mmc/host/dw_mmc.c
@@ -1116,8 +1116,8 @@ static void dw_mci_write_data_pio(struct dw_mci *host)
 	unsigned int nbytes = 0, len;
 
 	do {
-		len = SDMMC_FIFO_SZ -
-			(SDMMC_GET_FCNT(mci_readl(host, STATUS)) << shift);
+		len = (host->fifo_depth -
+			SDMMC_GET_FCNT(mci_readl(host, STATUS))) << shift;
 		if (offset + len <= sg->length) {
 			host->push_data(host, (void *)(buf + offset), len);
 
@@ -1659,8 +1659,19 @@ static int dw_mci_probe(struct platform_device *pdev)
 	 * FIFO threshold settings  RxMark  = fifo_size / 2 - 1,
 	 *                          Tx Mark = fifo_size / 2 DMA Size = 8
 	 */
-	fifo_size = mci_readl(host, FIFOTH);
-	fifo_size = (fifo_size >> 16) & 0x7ff;
+	if (!host->pdata->fifo_depth) {
+		/*
+		 * Power-on value of RX_WMark is FIFO_DEPTH-1, but this may
+		 * have been overwritten by the bootloader, just like we're
+		 * about to do, so if you know the value for your hardware, you
+		 * should put it in the platform data.
+		 */
+		fifo_size = mci_readl(host, FIFOTH);
+		fifo_size = 1 + ((fifo_size >> 16) & 0x7ff);
+	} else {
+		fifo_size = host->pdata->fifo_depth;
+	}
+	host->fifo_depth = fifo_size;
 	host->fifoth_val = ((0x2 << 28) | ((fifo_size/2 - 1) << 16) |
 			((fifo_size/2) << 0));
 	mci_writel(host, FIFOTH, host->fifoth_val);
@@ -1707,7 +1718,9 @@ static int dw_mci_probe(struct platform_device *pdev)
 	mci_writel(host, CTRL, SDMMC_CTRL_INT_ENABLE); /* Enable mci interrupt */
 
 	dev_info(&pdev->dev, "DW MMC controller at irq %d, "
-		 "%d bit host data width\n", irq, width);
+		 "%d bit host data width, "
+		 "%u deep fifo\n",
+		 irq, width, fifo_size);
 	if (host->quirks & DW_MCI_QUIRK_IDMAC_DTO)
 		dev_info(&pdev->dev, "Internal DMAC interrupt fix enabled.\n");
 
diff --git a/drivers/mmc/host/dw_mmc.h b/drivers/mmc/host/dw_mmc.h
index bb9e5de76ae9..027d37735394 100644
--- a/drivers/mmc/host/dw_mmc.h
+++ b/drivers/mmc/host/dw_mmc.h
@@ -118,7 +118,6 @@
 #define SDMMC_CMD_INDX(n)		((n) & 0x1F)
 /* Status register defines */
 #define SDMMC_GET_FCNT(x)		(((x)>>17) & 0x1FF)
-#define SDMMC_FIFO_SZ			32
 /* Internal DMAC interrupt defines */
 #define SDMMC_IDMAC_INT_AI		BIT(9)
 #define SDMMC_IDMAC_INT_NI		BIT(8)