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Fixed latency issue caused by disabling preemption for up to 5 seconds #72

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Fixed latency issue caused by disabling preemption for up to 5 seconds #72

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4 changes: 4 additions & 0 deletions drivers/mmc/host/sdhci.c
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Original file line number Diff line number Diff line change
Expand Up @@ -967,6 +967,7 @@ static void sdhci_send_command(struct sdhci_host *host, struct mmc_command *cmd)
if ((cmd->data != NULL) || (cmd->flags & MMC_RSP_BUSY))
mask |= SDHCI_DATA_INHIBIT;

// This may disable preemption for up to 5s! In real world cases we saw that preemption is stopped for ~150ms which is bad for realtime A/V streaming apps.
if(host->ops->missing_status && (cmd->opcode == MMC_SEND_STATUS)) {
timeout = 5000; // Really obscenely large delay to send the status, due to bug in controller
// which might cause the STATUS command to get stuck when a data operation is in flow
Expand All @@ -988,7 +989,10 @@ static void sdhci_send_command(struct sdhci_host *host, struct mmc_command *cmd)
return;
}
timeout--;
preempt_enable();
schedule();
mdelay(1);
preempt_disable();
}
DBG("send cmd %d - wait 0x%X irq 0x%x\n", cmd->opcode, mask,
sdhci_readl(host, SDHCI_INT_STATUS));
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