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Commit 833b5117 authored by Martin Hicks's avatar Martin Hicks Committed by Ulf Hansson
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mmc: Throttle calls to MMC_SEND_STATUS during mmc_do_erase() 



This drastically reduces the rate at which the MMC_SEND_STATUS cmd polls
for completion of the MMC Erase operation.  The patch does this by adding
a backoff sleep that starts by sleeping for short intervals (128-256us),
and ramps up to sleeping for 32-64ms.

Even on very quickly completing erase operations, the loop iterates a few
times, so not too much extra latency is added to these commands.

For long running discard operarations, like a full-device secure discard,
this change drops the interrupt rates on my single-core NXP I.MX6UL from
45000/s to about 20/s, and greatly improves system responsiveness.

Signed-off-by: default avatarMartin Hicks <mort@bork.org>
Signed-off-by: default avatarUlf Hansson <ulf.hansson@linaro.org>
parent a6720c02

drivers/mmc/core/core.c

+9 −2
Original line number Diff line number Diff line
@@ -1969,6 +1969,7 @@ static int mmc_do_erase(struct mmc_card *card, unsigned int from, 
	unsigned int qty = 0, busy_timeout = 0;

	bool use_r1b_resp = false;

	unsigned long timeout;

	int loop_udelay=64, udelay_max=32768;

	int err;



	mmc_retune_hold(card->host);
@@ -2093,9 +2094,15 @@ static int mmc_do_erase(struct mmc_card *card, unsigned int from, 
			err =  -EIO;

			goto out;

		}

		if ((cmd.resp[0] & R1_READY_FOR_DATA) &&

		    R1_CURRENT_STATE(cmd.resp[0]) != R1_STATE_PRG)

			break;



		usleep_range(loop_udelay, loop_udelay*2);

		if (loop_udelay < udelay_max)

			loop_udelay *= 2;

	} while (1);



	} while (!(cmd.resp[0] & R1_READY_FOR_DATA) ||

		 (R1_CURRENT_STATE(cmd.resp[0]) == R1_STATE_PRG));

out:

	mmc_retune_release(card->host);

	return err;