Hi,
Thanks you for the test.
here a new version of the patch. It doesn't replace mdelay with jiffies
anymore. It changes mdelay to udelay (the granularity of 1 ms becomes 10
us).
I didn't mesure irq off latency with this patch.
Matthieu
Kyungmin Park a écrit :
Hi,
Not good news. This patch make a hang at probe time.
it's tested against commit 7e27d6e778cd87b6f2415515d7127eba53fe5d02
Author: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Date: Fri Jun 11 19:14:04 2010 -0700
Linux 2.6.35-rc3
Thank you,
Kyungmin Park
On Thu, Jun 17, 2010 at 6:07 PM, Matthieu CASTET
<matthieu.castet@xxxxxxxxxx> wrote:
sdhci code got tasklets (sdhci_tasklet_card and sdhci_tasklet_finish),
that does :
{
spin_lock_irqsave
if (cond) {
sdhci_reset
sdhci_reset
}
spin_unlock_irqrestore
}
sdhci_reset {
...
while (read_reg) {
if (timeout == 0)
break;
timeout--;
mdelay(1);
}
...
}
The problem is that sdhci_reset [1] does busy pooling (with a granularity of
1 ms) on a register up to a timeout of 100 ms.
With the current code, we got irq off during 2*1ms. With the attached patch
we reduce irq off to 30 us.
Note that worst case 100 ms irq off still exist.
Signed-off-by: Matthieu CASTET <matthieu.castet@xxxxxxxxxx>
diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index c6d1bd8..fa06c70 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -157,7 +157,7 @@ static void sdhci_reset(struct sdhci_host *host, u8 mask)
host->clock = 0;
/* Wait max 100 ms */
- timeout = 100;
+ timeout = 100*100;
/* hw clears the bit when it's done */
while (sdhci_readb(host, SDHCI_SOFTWARE_RESET) & mask) {
@@ -168,7 +168,7 @@ static void sdhci_reset(struct sdhci_host *host, u8 mask)
return;
}
timeout--;
- mdelay(1);
+ udelay(10);
}
if (host->quirks & SDHCI_QUIRK_RESTORE_IRQS_AFTER_RESET)
@@ -882,7 +882,7 @@ static void sdhci_send_command(struct sdhci_host *host, struct mmc_command *cmd)
WARN_ON(host->cmd);
/* Wait max 10 ms */
- timeout = 10;
+ timeout = 10*100;
mask = SDHCI_CMD_INHIBIT;
if ((cmd->data != NULL) || (cmd->flags & MMC_RSP_BUSY))
@@ -903,7 +903,7 @@ static void sdhci_send_command(struct sdhci_host *host, struct mmc_command *cmd)
return;
}
timeout--;
- mdelay(1);
+ udelay(10);
}
mod_timer(&host->timer, jiffies + 10 * HZ);
@@ -1007,7 +1007,7 @@ static void sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
sdhci_writew(host, clk, SDHCI_CLOCK_CONTROL);
/* Wait max 20 ms */
- timeout = 20;
+ timeout = 20*100;
while (!((clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL))
& SDHCI_CLOCK_INT_STABLE)) {
if (timeout == 0) {
@@ -1017,7 +1017,7 @@ static void sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
return;
}
timeout--;
- mdelay(1);
+ udelay(10);
}
clk |= SDHCI_CLOCK_CARD_EN;
