mmc: dw_mmc: control card read threshold

Card Read Threshold should be ensured that the card clock does not stop
in the middle of a block of data being transferred from the card to the
Host. Specially, clock stop is allowed in fast transfer such as HS200
or SDR104 mode. And so, it should be enabled.

Signed-off-by: Seungwon Jeon <tgih.jun@samsung.com>
Tested-by: Alim Akhtar <alim.akhtar@samsung.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

drivers/mmc/host/dw_mmc.c

@@ -570,6 +570,37 @@ done:
 #endif
 }
 
+static void dw_mci_ctrl_rd_thld(struct dw_mci *host, struct mmc_data *data)
+{
+	unsigned int blksz = data->blksz;
+	u32 blksz_depth, fifo_depth;
+	u16 thld_size;
+
+	WARN_ON(!(data->flags & MMC_DATA_READ));
+
+	if (host->timing != MMC_TIMING_MMC_HS200 &&
+	    host->timing != MMC_TIMING_UHS_SDR104)
+		goto disable;
+
+	blksz_depth = blksz / (1 << host->data_shift);
+	fifo_depth = host->fifo_depth;
+
+	if (blksz_depth > fifo_depth)
+		goto disable;
+
+	/*
+	 * If (blksz_depth) >= (fifo_depth >> 1), should be 'thld_size <= blksz'
+	 * If (blksz_depth) <  (fifo_depth >> 1), should be thld_size = blksz
+	 * Currently just choose blksz.
+	 */
+	thld_size = blksz;
+	mci_writel(host, CDTHRCTL, SDMMC_SET_RD_THLD(thld_size, 1));
+	return;
+
+disable:
+	mci_writel(host, CDTHRCTL, SDMMC_SET_RD_THLD(0, 0));
+}
+
 static int dw_mci_submit_data_dma(struct dw_mci *host, struct mmc_data *data)
 {
 	int sg_len;
@@ -627,10 +658,12 @@ static void dw_mci_submit_data(struct dw_mci *host, struct mmc_data *data)
 	host->sg = NULL;
 	host->data = data;
 
-	if (data->flags & MMC_DATA_READ)
+	if (data->flags & MMC_DATA_READ) {
 		host->dir_status = DW_MCI_RECV_STATUS;
-	else
+		dw_mci_ctrl_rd_thld(host, data);
+	} else {
 		host->dir_status = DW_MCI_SEND_STATUS;
+	}
 
 	if (dw_mci_submit_data_dma(host, data)) {
 		int flags = SG_MITER_ATOMIC;
@@ -877,6 +910,7 @@ static void dw_mci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
 		regs &= ~((0x1 << slot->id) << 16);
 
 	mci_writel(slot->host, UHS_REG, regs);
+	slot->host->timing = ios->timing;
 
 	/*
 	 * Use mirror of ios->clock to prevent race with mmc

drivers/mmc/host/dw_mmc.h

@@ -53,6 +53,7 @@
 #define SDMMC_IDINTEN		0x090
 #define SDMMC_DSCADDR		0x094
 #define SDMMC_BUFADDR		0x098
+#define SDMMC_CDTHRCTL		0x100
 #define SDMMC_DATA(x)		(x)
 
 /*
@@ -146,6 +147,8 @@
 #define SDMMC_IDMAC_SWRESET		BIT(0)
 /* Version ID register define */
 #define SDMMC_GET_VERID(x)		((x) & 0xFFFF)
+/* Card read threshold */
+#define SDMMC_SET_RD_THLD(v, x)		(((v) & 0x1FFF) << 16 | (x))
 
 /* Register access macros */
 #define mci_readl(dev, reg)			\

include/linux/mmc/dw_mmc.h

@@ -130,6 +130,7 @@ struct dw_mci {
 	struct mmc_command	*cmd;
 	struct mmc_data		*data;
 	unsigned int		prev_blksz;
+	unsigned char		timing;
 	struct workqueue_struct	*card_workqueue;
 
 	/* DMA interface members*/