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: Mark Lord <mlord@pobox.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
diff --git a/drivers/ata/sata_mv.c b/drivers/ata/sata_mv.c
index 206220e..ef38545 100644
--- a/drivers/ata/sata_mv.c
+++ b/drivers/ata/sata_mv.c
@@ -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_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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
* 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 @@
/* 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 @@
/* 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 @@
* 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;
}