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mmc: Throttle calls to MMC_SEND_STATUS during mmc_do_erase()

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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: Martin Hicks <mort@bork.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
This commit is contained in:
Martin Hicks 2018-05-28 13:23:04 +02:00 committed by Ulf Hansson
parent a6720c023a
commit 833b51170f
1 changed files with 9 additions and 2 deletions
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11
drivers/mmc/core/core.c
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@ -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;