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Commit 2b748a0a authored by Mark Lord's avatar Mark Lord Committed by Jeff Garzik
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sata_mv: implement IRQ coalescing (v2) 



Add IRQ coalescing to sata_mv (off by default).

This feature can reduce total interrupt overhead for RAID setups
in some situations, by deferring the interrupt signal until one or both of:

 a) a specified io_count (completed SATA commands) is achieved, or
 b) a specified time interval elapses after an IO completion.

For now, module parameters are used to set the irq_coalescing_io_count
and irq_coalescing_usecs (timeout) globally.  These may eventually
be supplemented with sysfs attributes, so that thresholds can be set
on-the-fly and on a per-chip (or even per-host_controller) basis.

Signed-off-by: default avatarMark Lord <mlord@pobox.com>
Signed-off-by: default avatarJeff Garzik <jgarzik@redhat.com>
parent 40f21b11

drivers/ata/sata_mv.c

+135 −8
Original line number Diff line number Diff line
@@ -34,10 +34,7 @@ 
 *

 * --> Develop a low-power-consumption strategy, and implement it.

 *

 * --> [Experiment, low priority] Investigate interrupt coalescing.

 *       Quite often, especially with PCI Message Signalled Interrupts (MSI),

 *       the overhead reduced by interrupt mitigation is quite often not

 *       worth the latency cost.

 * --> Add sysfs attributes for per-chip / per-HC IRQ coalescing thresholds.

 *

 * --> [Experiment, Marvell value added] Is it possible to use target

 *       mode to cross-connect two Linux boxes with Marvell cards?  If so,
@@ -67,7 +64,7 @@ 
#include <linux/libata.h>



#define DRV_NAME	"sata_mv"

#define DRV_VERSION	"1.26"

#define DRV_VERSION	"1.27"



/*

 * module options
@@ -79,6 +76,16 @@ module_param(msi, int, S_IRUGO); 
MODULE_PARM_DESC(msi, "Enable use of PCI MSI (0=off, 1=on)");

#endif



static int irq_coalescing_io_count;

module_param(irq_coalescing_io_count, int, S_IRUGO);

MODULE_PARM_DESC(irq_coalescing_io_count,

		 "IRQ coalescing I/O count threshold (0..255)");



static int irq_coalescing_usecs;

module_param(irq_coalescing_usecs, int, S_IRUGO);

MODULE_PARM_DESC(irq_coalescing_usecs,

		 "IRQ coalescing time threshold in usecs");



enum {

	/* BAR's are enumerated in terms of pci_resource_start() terms */

	MV_PRIMARY_BAR		= 0,	/* offset 0x10: memory space */
@@ -88,8 +95,33 @@ enum { 
	MV_MAJOR_REG_AREA_SZ	= 0x10000,	/* 64KB */

	MV_MINOR_REG_AREA_SZ	= 0x2000,	/* 8KB */



	/* For use with both IRQ coalescing methods ("all ports" or "per-HC" */

	COAL_CLOCKS_PER_USEC	= 150,		/* for calculating COAL_TIMEs */

	MAX_COAL_TIME_THRESHOLD	= ((1 << 24) - 1), /* internal clocks count */

	MAX_COAL_IO_COUNT	= 255,		/* completed I/O count */



	MV_PCI_REG_BASE		= 0,



	/*

	 * Per-chip ("all ports") interrupt coalescing feature.

	 * This is only for GEN_II / GEN_IIE hardware.

	 *

	 * Coalescing defers the interrupt until either the IO_THRESHOLD

	 * (count of completed I/Os) is met, or the TIME_THRESHOLD is met.

	 */

	MV_COAL_REG_BASE	= 0x18000,

	MV_IRQ_COAL_CAUSE	= (MV_COAL_REG_BASE + 0x08),

	ALL_PORTS_COAL_IRQ	= (1 << 4),	/* all ports irq event */



	MV_IRQ_COAL_IO_THRESHOLD   = (MV_COAL_REG_BASE + 0xcc),

	MV_IRQ_COAL_TIME_THRESHOLD = (MV_COAL_REG_BASE + 0xd0),



	/*

	 * Registers for the (unused here) transaction coalescing feature:

	 */

	MV_TRAN_COAL_CAUSE_LO	= (MV_COAL_REG_BASE + 0x88),

	MV_TRAN_COAL_CAUSE_HI	= (MV_COAL_REG_BASE + 0x8c),



	MV_SATAHC0_REG_BASE	= 0x20000,

	MV_FLASH_CTL_OFS	= 0x1046c,

	MV_GPIO_PORT_CTL_OFS	= 0x104f0,
@@ -186,6 +218,8 @@ enum { 
	DONE_IRQ		= (1 << 1),	/* shift by (2 * port #) */

	HC0_IRQ_PEND		= 0x1ff,	/* bits 0-8 = HC0's ports */

	HC_SHIFT		= 9,		/* bits 9-17 = HC1's ports */

	DONE_IRQ_0_3		= 0x000000aa,	/* DONE_IRQ ports 0,1,2,3 */

	DONE_IRQ_4_7		= (DONE_IRQ_0_3 << HC_SHIFT),  /* 4,5,6,7 */

	PCI_ERR			= (1 << 18),

	TRAN_COAL_LO_DONE	= (1 << 19),	/* transaction coalescing */

	TRAN_COAL_HI_DONE	= (1 << 20),	/* transaction coalescing */
@@ -207,6 +241,16 @@ enum { 
	HC_COAL_IRQ		= (1 << 4),	/* IRQ coalescing */

	DEV_IRQ			= (1 << 8),	/* shift by port # */



	/*

	 * Per-HC (Host-Controller) interrupt coalescing feature.

	 * This is present on all chip generations.

	 *

	 * Coalescing defers the interrupt until either the IO_THRESHOLD

	 * (count of completed I/Os) is met, or the TIME_THRESHOLD is met.

	 */

	HC_IRQ_COAL_IO_THRESHOLD_OFS	= 0x000c,

	HC_IRQ_COAL_TIME_THRESHOLD_OFS	= 0x0010,



	/* Shadow block registers */

	SHD_BLK_OFS		= 0x100,

	SHD_CTL_AST_OFS		= 0x20,		/* ofs from SHD_BLK_OFS */
@@ -897,6 +941,23 @@ static void mv_set_edma_ptrs(void __iomem *port_mmio, 
		 port_mmio + EDMA_RSP_Q_OUT_PTR_OFS);

}



static void mv_write_main_irq_mask(u32 mask, struct mv_host_priv *hpriv)

{

	/*

	 * When writing to the main_irq_mask in hardware,

	 * we must ensure exclusivity between the interrupt coalescing bits

	 * and the corresponding individual port DONE_IRQ bits.

	 *

	 * Note that this register is really an "IRQ enable" register,

	 * not an "IRQ mask" register as Marvell's naming might suggest.

	 */

	if (mask & (ALL_PORTS_COAL_DONE | PORTS_0_3_COAL_DONE))

		mask &= ~DONE_IRQ_0_3;

	if (mask & (ALL_PORTS_COAL_DONE | PORTS_4_7_COAL_DONE))

		mask &= ~DONE_IRQ_4_7;

	writelfl(mask, hpriv->main_irq_mask_addr);

}



static void mv_set_main_irq_mask(struct ata_host *host,

				 u32 disable_bits, u32 enable_bits)

{
@@ -907,7 +968,7 @@ static void mv_set_main_irq_mask(struct ata_host *host, 
	new_mask = (old_mask & ~disable_bits) | enable_bits;

	if (new_mask != old_mask) {

		hpriv->main_irq_mask = new_mask;

		writelfl(new_mask, hpriv->main_irq_mask_addr);

		mv_write_main_irq_mask(new_mask, hpriv);

	}

}
@@ -948,6 +1009,64 @@ static void mv_clear_and_enable_port_irqs(struct ata_port *ap, 
	mv_enable_port_irqs(ap, port_irqs);

}



static void mv_set_irq_coalescing(struct ata_host *host,

				  unsigned int count, unsigned int usecs)

{

	struct mv_host_priv *hpriv = host->private_data;

	void __iomem *mmio = hpriv->base, *hc_mmio;

	u32 coal_enable = 0;

	unsigned long flags;

	unsigned int clks;

	const u32 coal_disable = PORTS_0_3_COAL_DONE | PORTS_4_7_COAL_DONE |

							ALL_PORTS_COAL_DONE;



	/* Disable IRQ coalescing if either threshold is zero */

	if (!usecs || !count) {

		clks = count = 0;

	} else {

		/* Respect maximum limits of the hardware */

		clks = usecs * COAL_CLOCKS_PER_USEC;

		if (clks > MAX_COAL_TIME_THRESHOLD)

			clks = MAX_COAL_TIME_THRESHOLD;

		if (count > MAX_COAL_IO_COUNT)

			count = MAX_COAL_IO_COUNT;

	}



	spin_lock_irqsave(&host->lock, flags);



#if 0 /* disabled pending functional clarification from Marvell */

	if (!IS_GEN_I(hpriv)) {

		/*

		 * GEN_II/GEN_IIE: global thresholds for the entire chip.

		 */

		writel(clks,  mmio + MV_IRQ_COAL_TIME_THRESHOLD);

		writel(count, mmio + MV_IRQ_COAL_IO_THRESHOLD);

		/* clear leftover coal IRQ bit */

		writelfl(~ALL_PORTS_COAL_IRQ, mmio + MV_IRQ_COAL_CAUSE);

		clks = count = 0; /* so as to clear the alternate regs below */

		coal_enable = ALL_PORTS_COAL_DONE;

	}

#endif

	/*

	 * All chips: independent thresholds for each HC on the chip.

	 */

	hc_mmio = mv_hc_base_from_port(mmio, 0);

	writel(clks,  hc_mmio + HC_IRQ_COAL_TIME_THRESHOLD_OFS);

	writel(count, hc_mmio + HC_IRQ_COAL_IO_THRESHOLD_OFS);

	coal_enable |= PORTS_0_3_COAL_DONE;

	if (hpriv->n_ports > 4) {

		hc_mmio = mv_hc_base_from_port(mmio, MV_PORTS_PER_HC);

		writel(clks,  hc_mmio + HC_IRQ_COAL_TIME_THRESHOLD_OFS);

		writel(count, hc_mmio + HC_IRQ_COAL_IO_THRESHOLD_OFS);

		coal_enable |= PORTS_4_7_COAL_DONE;

	}

	if (!count)

		coal_enable = 0;

	mv_set_main_irq_mask(host, coal_disable, coal_enable);



	spin_unlock_irqrestore(&host->lock, flags);

}



/**

 *      mv_start_edma - Enable eDMA engine

 *      @base: port base address
@@ -2500,6 +2619,10 @@ static int mv_host_intr(struct ata_host *host, u32 main_irq_cause) 
	void __iomem *mmio = hpriv->base, *hc_mmio;

	unsigned int handled = 0, port;



	/* If asserted, clear the "all ports" IRQ coalescing bit */

	if (main_irq_cause & ALL_PORTS_COAL_DONE)

		writel(~ALL_PORTS_COAL_IRQ, mmio + MV_IRQ_COAL_CAUSE);



	for (port = 0; port < hpriv->n_ports; port++) {

		struct ata_port *ap = host->ports[port];

		unsigned int p, shift, hardport, port_cause;
@@ -2532,6 +2655,8 @@ static int mv_host_intr(struct ata_host *host, u32 main_irq_cause) 
			 * to ack (only) those ports via hc_irq_cause.

			 */

			ack_irqs = 0;

			if (hc_cause & PORTS_0_3_COAL_DONE)

				ack_irqs = HC_COAL_IRQ;

			for (p = 0; p < MV_PORTS_PER_HC; ++p) {

				if ((port + p) >= hpriv->n_ports)

					break;
@@ -2620,7 +2745,7 @@ static irqreturn_t mv_interrupt(int irq, void *dev_instance) 


	/* for MSI:  block new interrupts while in here */

	if (using_msi)

		writel(0, hpriv->main_irq_mask_addr);

		mv_write_main_irq_mask(0, hpriv);



	main_irq_cause = readl(hpriv->main_irq_cause_addr);

	pending_irqs   = main_irq_cause & hpriv->main_irq_mask;
@@ -2637,7 +2762,7 @@ static irqreturn_t mv_interrupt(int irq, void *dev_instance) 


	/* for MSI: unmask; interrupt cause bits will retrigger now */

	if (using_msi)

		writel(hpriv->main_irq_mask, hpriv->main_irq_mask_addr);

		mv_write_main_irq_mask(hpriv->main_irq_mask, hpriv);



	spin_unlock(&host->lock);
@@ -3546,6 +3671,8 @@ static int mv_init_host(struct ata_host *host, unsigned int board_idx) 
	 * The per-port interrupts get done later as ports are set up.

	 */

	mv_set_main_irq_mask(host, 0, PCI_ERR);

	mv_set_irq_coalescing(host, irq_coalescing_io_count,

				    irq_coalescing_usecs);

done:

	return rc;

}