mmc: sdricoh_cs: Throttle polling rate for commands

Rather than to poll in a busy-loop, let's convert into using
read_poll_timeout() and insert a small delay between each polling attempts.
In particular, this avoids hogging the CPU.

Additionally, to convert to read_poll_timeout() we also need to switch from
using a specific number of polling attempts, into a specific timeout in us
instead. The previous 100000 attempts, is translated into a total timeout
of total 1s, as that seemed like reasonable value to pick.

Cc: Sascha Sommer <saschasommer@freenet.de>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20200508095218.14177-1-ulf.hansson@linaro.org

diff --git a/drivers/mmc/host/sdricoh_cs.c b/drivers/mmc/host/sdricoh_cs.c
index 8392158e2e9f6432d53795bc7c85a09fbce51e2d..0594b5ffe15144a581b9e1f62ec0ee73835b286e 100644 (file)
--- a/drivers/mmc/host/sdricoh_cs.c
+++ b/drivers/mmc/host/sdricoh_cs.c
@@ -59,7 +59,7 @@ static unsigned int switchlocked;
 #define STATUS_BUSY              0x40000000
 
 /* timeouts */
-#define CMD_TIMEOUT       100000
+#define SDRICOH_CMD_TIMEOUT_US 1000000
 #define SDRICOH_DATA_TIMEOUT_US        1000000
 
 /* list of supported pcmcia devices */
@@ -158,8 +158,7 @@ static int sdricoh_query_status(struct sdricoh_host *host, unsigned int wanted)
 static int sdricoh_mmc_cmd(struct sdricoh_host *host, struct mmc_command *cmd)
 {
        unsigned int status;
-       int result = 0;
-       unsigned int loop = 0;
+       int ret;
        unsigned char opcode = cmd->opcode;
 
        /* reset status reg? */
@@ -175,24 +174,24 @@ static int sdricoh_mmc_cmd(struct sdricoh_host *host, struct mmc_command *cmd)
        /* fill parameters */
        sdricoh_writel(host, R204_CMD_ARG, cmd->arg);
        sdricoh_writel(host, R200_CMD, (0x10000 << 8) | opcode);
+
        /* wait for command completion */
-       if (opcode) {
-               for (loop = 0; loop < CMD_TIMEOUT; loop++) {
-                       status = sdricoh_readl(host, R21C_STATUS);
-                       sdricoh_writel(host, R2E4_STATUS_RESP, status);
-                       if (status  & STATUS_CMD_FINISHED)
-                               break;
-               }
-               /* don't check for timeout in the loop it is not always
-                  reset correctly
-               */
-               if (loop == CMD_TIMEOUT || status & STATUS_CMD_TIMEOUT)
-                       result = -ETIMEDOUT;
+       if (!opcode)
+               return 0;
 
-       }
+       ret = read_poll_timeout(sdricoh_readl, status,
+                       sdricoh_status_ok(host, status, STATUS_CMD_FINISHED),
+                       32, SDRICOH_CMD_TIMEOUT_US, false,
+                       host, R21C_STATUS);
 
-       return result;
+       /*
+        * Don't check for timeout status in the loop, as it's not always reset
+        * correctly.
+        */
+       if (ret || status & STATUS_CMD_TIMEOUT)
+               return -ETIMEDOUT;
 
+       return 0;
 }
 
 static int sdricoh_reset(struct sdricoh_host *host)