Commit 3eea697c authored by Ulf Hansson's avatar Ulf Hansson
Browse files

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: default avatarUlf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20200508095218.14177-1-ulf.hansson@linaro.org
parent eadb7897

drivers/mmc/host/sdricoh_cs.c

+16 −17
Original line number Diff line number Diff line
@@ -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)

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