sdhci: let the controller wait for busy state to end

The sdhci controllers can interrupt us when the busy state from the
card has ended, saving CPU cycles and power.

Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>

1 files changed, 33 insertions, 6 deletions

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index e3a8133560a2..ef461274397b 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -1266,9 +1266,31 @@ static void sdhci_cmd_irq(struct sdhci_host *host, u32 intmask)
                         SDHCI_INT_INDEX))
                 host->cmd->error = -EILSEQ;
 
-        if (host->cmd->error)
+        if (host->cmd->error) {
                 tasklet_schedule(&host->finish_tasklet);
-        else if (intmask & SDHCI_INT_RESPONSE)
+                return;
+        }
+
+        /*
+         * The host can send and interrupt when the busy state has
+         * ended, allowing us to wait without wasting CPU cycles.
+         * Unfortunately this is overloaded on the "data complete"
+         * interrupt, so we need to take some care when handling
+         * it.
+         *
+         * Note: The 1.0 specification is a bit ambiguous about this
+         *       feature so there might be some problems with older
+         *       controllers.
+         */
+        if (host->cmd->flags & MMC_RSP_BUSY) {
+                if (host->cmd->data)
+                        DBG("Cannot wait for busy signal when also "
+                                "doing a data transfer");
+                else
+                        return;
+        }
+
+        if (intmask & SDHCI_INT_RESPONSE)
                 sdhci_finish_command(host);
 }
 
@@ -1278,11 +1300,16 @@ static void sdhci_data_irq(struct sdhci_host *host, u32 intmask)
 
         if (!host->data) {
                 /*
-                 * A data end interrupt is sent together with the response
-                 * for the stop command.
+                 * The "data complete" interrupt is also used to
+                 * indicate that a busy state has ended. See comment
+                 * above in sdhci_cmd_irq().
                  */
-                if (intmask & SDHCI_INT_DATA_END)
-                        return;
+                if (host->cmd && (host->cmd->flags & MMC_RSP_BUSY)) {
+                        if (intmask & SDHCI_INT_DATA_END) {
+                                sdhci_finish_command(host);
+                                return;
+                        }
+                }
 
                 printk(KERN_ERR "%s: Got data interrupt 0x%08x even "
                         "though no data operation was in progress.\n",