sunxi: improve throughput in the sunxi_mmc driver

Throughput tests have shown the sunxi_mmc driver to take over 10s to
read 10MB from a fast eMMC device due to excessive delays in polling
loops.

This commit restructures the main polling loops to use get_timer(...)
to determine whether a (millisecond) timeout has expired.  We choose
not to use the wait_bit function, as we don't need interruptability
with ctrl-c and have at least one case where two bits (one for an
error condition and another one for completion) need to be read and
using wait_bit would have not added to the clarity.

The observed speedup in testing on a A31 is greater than 10x (e.g. a
10MB write decreases from 9.302s to 0.884s).

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Tested-by: Mylène Josserand <mylene.josserand@bootlin.com>
Acked-by: Jagan Teki <jagan@openedev.com>
Reviewed-by: Tom Rini <trini@konsulko.com>

diff --git a/drivers/mmc/sunxi_mmc.c b/drivers/mmc/sunxi_mmc.c
index f4c245c..5292f2d 100644 (file)
--- a/drivers/mmc/sunxi_mmc.c
+++ b/drivers/mmc/sunxi_mmc.c
@@ -188,15 +188,16 @@ static int mmc_update_clk(struct sunxi_mmc_priv *priv)
 {
        unsigned int cmd;
        unsigned timeout_msecs = 2000;
+       unsigned long start = get_timer(0);
 
        cmd = SUNXI_MMC_CMD_START |
              SUNXI_MMC_CMD_UPCLK_ONLY |
              SUNXI_MMC_CMD_WAIT_PRE_OVER;
+
        writel(cmd, &priv->reg->cmd);
        while (readl(&priv->reg->cmd) & SUNXI_MMC_CMD_START) {
-               if (!timeout_msecs--)
+               if (get_timer(start) > timeout_msecs)
                        return -1;
-               udelay(1000);
        }
 
        /* clock update sets various irq status bits, clear these */
@@ -277,18 +278,21 @@ static int mmc_trans_data_by_cpu(struct sunxi_mmc_priv *priv, struct mmc *mmc,
        unsigned i;
        unsigned *buff = (unsigned int *)(reading ? data->dest : data->src);
        unsigned byte_cnt = data->blocksize * data->blocks;
-       unsigned timeout_usecs = (byte_cnt >> 8) * 1000;
-       if (timeout_usecs < 2000000)
-               timeout_usecs = 2000000;
+       unsigned timeout_msecs = byte_cnt >> 8;
+       unsigned long  start;
+
+       if (timeout_msecs < 2000)
+               timeout_msecs = 2000;
 
        /* Always read / write data through the CPU */
        setbits_le32(&priv->reg->gctrl, SUNXI_MMC_GCTRL_ACCESS_BY_AHB);
 
+       start = get_timer(0);
+
        for (i = 0; i < (byte_cnt >> 2); i++) {
                while (readl(&priv->reg->status) & status_bit) {
-                       if (!timeout_usecs--)
+                       if (get_timer(start) > timeout_msecs)
                                return -1;
-                       udelay(1);
                }
 
                if (reading)
@@ -304,16 +308,16 @@ static int mmc_rint_wait(struct sunxi_mmc_priv *priv, struct mmc *mmc,
                         uint timeout_msecs, uint done_bit, const char *what)
 {
        unsigned int status;
+       unsigned long start = get_timer(0);
 
        do {
                status = readl(&priv->reg->rint);
-               if (!timeout_msecs-- ||
+               if ((get_timer(start) > timeout_msecs) ||
                    (status & SUNXI_MMC_RINT_INTERRUPT_ERROR_BIT)) {
                        debug("%s timeout %x\n", what,
                              status & SUNXI_MMC_RINT_INTERRUPT_ERROR_BIT);
                        return -ETIMEDOUT;
                }
-               udelay(1000);
        } while (!(status & done_bit));
 
        return 0;
@@ -405,15 +409,16 @@ static int sunxi_mmc_send_cmd_common(struct sunxi_mmc_priv *priv,
        }
 
        if (cmd->resp_type & MMC_RSP_BUSY) {
+               unsigned long start = get_timer(0);
                timeout_msecs = 2000;
+
                do {
                        status = readl(&priv->reg->status);
-                       if (!timeout_msecs--) {
+                       if (get_timer(start) > timeout_msecs) {
                                debug("busy timeout\n");
                                error = -ETIMEDOUT;
                                goto out;
                        }
-                       udelay(1000);
                } while (status & SUNXI_MMC_STATUS_CARD_DATA_BUSY);
        }