[PATCH 06/10] sdhci: Add quirk to suppress PIO interrupts during DMA transfers

[Anton Vorontsov]

Some hosts (that is, FSL eSDHC) throw PIO interrupts during DMA
transfers, this causes tons of unneeded interrupts, and thus highly
degraded speed.

This patch adds SDHCI_QUIRK_PIO_IRQS_DURING_DMA quirk. When specified,
the sdhci driver will disable PIO interrupts during DMA transfers.

Signed-off-by: Anton Vorontsov <avorontsov at ru.mvista.com>
---
 drivers/mmc/host/sdhci.c |   30 ++++++++++++++++++++++++++++++
 drivers/mmc/host/sdhci.h |    3 +++
 2 files changed, 33 insertions(+), 0 deletions(-)

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index c3737fe..57b8ffe 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -589,6 +589,33 @@ static u8 sdhci_calc_timeout(struct sdhci_host *host, struct mmc_data *data)
 	return count;
 }
 
+static void sdhci_set_pio_irqs(struct sdhci_host *host, bool state)
+{
+	bool current_state = !(host->flags & SDHCI_PIO_DISABLED);
+	u32 ier;
+
+	/*
+	 * We only care about PIO IRQs if the host issues PIO IRQs during
+	 * DMA transfers. Otherwise we can keep the irqs always enabled.
+	 */
+	if (!(host->quirks & SDHCI_QUIRK_PIO_IRQS_DURING_DMA))
+		return;
+
+	if (current_state == state)
+		return;
+
+	ier = sdhci_readl(host, SDHCI_INT_ENABLE);
+	if (state) {
+		ier |= SDHCI_INT_DATA_AVAIL | SDHCI_INT_SPACE_AVAIL;
+		host->flags &= ~SDHCI_PIO_DISABLED;
+	} else {
+		ier &= ~(SDHCI_INT_DATA_AVAIL | SDHCI_INT_SPACE_AVAIL);
+		host->flags |= SDHCI_PIO_DISABLED;
+	}
+	sdhci_writel(host, SDHCI_INT_ENABLE, ier);
+	sdhci_writel(host, SDHCI_SIGNAL_ENABLE, ier);
+}
+
 static void sdhci_prepare_data(struct sdhci_host *host, struct mmc_data *data)
 {
 	u8 count;
@@ -735,6 +762,9 @@ static void sdhci_prepare_data(struct sdhci_host *host, struct mmc_data *data)
 		sg_miter_start(&host->sg_miter,
 			data->sg, data->sg_len, SG_MITER_ATOMIC);
 		host->blocks = data->blocks;
+		sdhci_set_pio_irqs(host, true);
+	} else {
+		sdhci_set_pio_irqs(host, false);
 	}
 
 	/* We do not handle DMA boundaries, so set it to max (512 KiB) */
diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
index 2747340..7e3b01f 100644
--- a/drivers/mmc/host/sdhci.h
+++ b/drivers/mmc/host/sdhci.h
@@ -221,6 +221,8 @@ struct sdhci_host {
 #define SDHCI_QUIRK_INVERTED_WRITE_PROTECT		(1<<17)
 /* Controller has all registers of 32 bit width */
 #define SDHCI_QUIRK_32BIT_REGISTERS			(1<<18)
+/* Controller issues PIO interrupts during DMA transfers */
+#define SDHCI_QUIRK_PIO_IRQS_DURING_DMA			(1<<19)
 
 	int			irq;		/* Device IRQ */
 	void __iomem *		ioaddr;		/* Mapped address */
@@ -242,6 +244,7 @@ struct sdhci_host {
 #define SDHCI_USE_ADMA		(1<<1)		/* Host is ADMA capable */
 #define SDHCI_REQ_USE_DMA	(1<<2)		/* Use DMA for this req. */
 #define SDHCI_DEVICE_DEAD	(1<<3)		/* Device unresponsive */
+#define SDHCI_PIO_DISABLED	(1<<4)		/* PIO IRQs disabled */
 
 	unsigned int		version;	/* SDHCI spec. version */
 
-- 
1.5.6.5