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

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Date:	Thu, 22 Jan 2009 05:00:32 +0300
From:	Anton Vorontsov <avorontsov@...mvista.com>
To:	Pierre Ossman <drzeus-sdhci@...eus.cx>
Cc:	Ben Dooks <ben-linux@...ff.org>, Arnd Bergmann <arnd@...db.de>,
	Kumar Gala <galak@...nel.crashing.org>,
	Liu Dave <DaveLiu@...escale.com>,
	Xie Xiaobo <X.Xie@...escale.com>,
	Konjin Lai <Konjin.Lai@...escale.com>,
	Joe D'Abbraccio <Joe.D'abbraccio@...escale.com>,
	sdhci-devel@...t.drzeus.cx, linux-kernel@...r.kernel.org,
	linuxppc-dev@...abs.org
Subject: [PATCH 06/10] sdhci: Add quirk to suppress PIO interrupts during
	DMA transfers

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@...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

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