Hi Matthieu,
This patch didn't make it upstream. Kyungmin offered a suggestion for
fixing it -- would you like to resend an updated patch?
(As a minor aside, I have a fairly irrational preference for
"time_after(jiffies, timeout)" over "time_is_before_jiffies(timeout)",
because the latter reads as the inverse of what it actually does to me.
They compile to the same code.)
Date: Thu, 17 Jun 2010 11:07:15 +0200
From: Matthieu CASTET <matthieu.castet@xxxxxxxxxx>
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>
Signed-off-by: Chris Ball <cjb@xxxxxxxxxx>
---
diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index c6d1bd8..03d6bde 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -157,18 +157,17 @@ static void sdhci_reset(struct sdhci_host *host, u8 mask)
host->clock = 0;
/* Wait max 100 ms */
- timeout = 100;
+ timeout = jiffies + msecs_to_jiffies(100);
/* hw clears the bit when it's done */
while (sdhci_readb(host, SDHCI_SOFTWARE_RESET) & mask) {
- if (timeout == 0) {
+ if (time_is_before_jiffies(timeout)) {
printk(KERN_ERR "%s: Reset 0x%x never completed.\n",
mmc_hostname(host->mmc), (int)mask);
sdhci_dumpregs(host);
return;
}
- timeout--;
- mdelay(1);
+ cpu_relax();
}
if (host->quirks & SDHCI_QUIRK_RESTORE_IRQS_AFTER_RESET)
@@ -882,7 +881,7 @@ static void sdhci_send_command(struct sdhci_host *host, struct mmc_command *cmd)
WARN_ON(host->cmd);
/* Wait max 10 ms */
- timeout = 10;
+ timeout = jiffies + msecs_to_jiffies(10);
mask = SDHCI_CMD_INHIBIT;
if ((cmd->data != NULL) || (cmd->flags & MMC_RSP_BUSY))
@@ -894,7 +893,7 @@ static void sdhci_send_command(struct sdhci_host *host, struct mmc_command *cmd)
mask &= ~SDHCI_DATA_INHIBIT;
while (sdhci_readl(host, SDHCI_PRESENT_STATE) & mask) {
- if (timeout == 0) {
+ if (time_is_before_jiffies(timeout)) {
printk(KERN_ERR "%s: Controller never released "
"inhibit bit(s).\n", mmc_hostname(host->mmc));
sdhci_dumpregs(host);
@@ -902,8 +901,7 @@ static void sdhci_send_command(struct sdhci_host *host, struct mmc_command *cmd)
tasklet_schedule(&host->finish_tasklet);
return;
}
- timeout--;
- mdelay(1);
+ cpu_relax();
}
mod_timer(&host->timer, jiffies + 10 * HZ);
@@ -1007,17 +1005,16 @@ 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 = jiffies + msecs_to_jiffies(20)
while (!((clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL))
& SDHCI_CLOCK_INT_STABLE)) {
- if (timeout == 0) {
+ if (time_is_before_jiffies(timeout)) {
printk(KERN_ERR "%s: Internal clock never "
"stabilised.\n", mmc_hostname(host->mmc));
sdhci_dumpregs(host);
return;
}
- timeout--;
- mdelay(1);
+ cpu_relax();
}
clk |= SDHCI_CLOCK_CARD_EN;
--
Chris Ball <cjb@xxxxxxxxxx> <http://printf.net/>
One Laptop Per Child
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