X-Git-Url: http://pileus.org/git/?a=blobdiff_plain;f=arch%2Fx86%2Fkernel%2Fhpet.c;h=aff0b3c2750929aff9f36ccf946f4a7ae31b1afa;hb=2c518959f082c549d6c6dd9b5380aec40c3eb07f;hp=7494999141b3ae9c9ab67302481a2e6c15e969e6;hpb=1053e6bba091d9d18797f7789df6a7ef8735f20c;p=~andy%2Flinux

diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c
index 7494999141b..aff0b3c2750 100644
--- a/arch/x86/kernel/hpet.c
+++ b/arch/x86/kernel/hpet.c
@@ -380,44 +380,35 @@ static int hpet_next_event(unsigned long delta,
 			   struct clock_event_device *evt, int timer)
 {
 	u32 cnt;
+	s32 res;
 
 	cnt = hpet_readl(HPET_COUNTER);
 	cnt += (u32) delta;
 	hpet_writel(cnt, HPET_Tn_CMP(timer));
 
 	/*
-	 * We need to read back the CMP register on certain HPET
-	 * implementations (ATI chipsets) which seem to delay the
-	 * transfer of the compare register into the internal compare
-	 * logic. With small deltas this might actually be too late as
-	 * the counter could already be higher than the compare value
-	 * at that point and we would wait for the next hpet interrupt
-	 * forever. We found out that reading the CMP register back
-	 * forces the transfer so we can rely on the comparison with
-	 * the counter register below. If the read back from the
-	 * compare register does not match the value we programmed
-	 * then we might have a real hardware problem. We can not do
-	 * much about it here, but at least alert the user/admin with
-	 * a prominent warning.
-	 *
-	 * An erratum on some chipsets (ICH9,..), results in
-	 * comparator read immediately following a write returning old
-	 * value. Workaround for this is to read this value second
-	 * time, when first read returns old value.
-	 *
-	 * In fact the write to the comparator register is delayed up
-	 * to two HPET cycles so the workaround we tried to restrict
-	 * the readback to those known to be borked ATI chipsets
-	 * failed miserably. So we give up on optimizations forever
-	 * and penalize all HPET incarnations unconditionally.
+	 * HPETs are a complete disaster. The compare register is
+	 * based on a equal comparison and neither provides a less
+	 * than or equal functionality (which would require to take
+	 * the wraparound into account) nor a simple count down event
+	 * mode. Further the write to the comparator register is
+	 * delayed internally up to two HPET clock cycles in certain
+	 * chipsets (ATI, ICH9,10). We worked around that by reading
+	 * back the compare register, but that required another
+	 * workaround for ICH9,10 chips where the first readout after
+	 * write can return the old stale value. We already have a
+	 * minimum delta of 5us enforced, but a NMI or SMI hitting
+	 * between the counter readout and the comparator write can
+	 * move us behind that point easily. Now instead of reading
+	 * the compare register back several times, we make the ETIME
+	 * decision based on the following: Return ETIME if the
+	 * counter value after the write is less than 8 HPET cycles
+	 * away from the event or if the counter is already ahead of
+	 * the event.
 	 */
-	if (unlikely((u32)hpet_readl(HPET_Tn_CMP(timer)) != cnt)) {
-		if (hpet_readl(HPET_Tn_CMP(timer)) != cnt)
-			printk_once(KERN_WARNING
-				"hpet: compare register read back failed.\n");
-	}
+	res = (s32)(cnt - hpet_readl(HPET_COUNTER));
 
-	return (s32)(hpet_readl(HPET_COUNTER) - cnt) >= 0 ? -ETIME : 0;
+	return res < 8 ? -ETIME : 0;
 }
 
 static void hpet_legacy_set_mode(enum clock_event_mode mode,
@@ -440,9 +431,9 @@ static int hpet_legacy_next_event(unsigned long delta,
 static DEFINE_PER_CPU(struct hpet_dev *, cpu_hpet_dev);
 static struct hpet_dev	*hpet_devs;
 
-void hpet_msi_unmask(unsigned int irq)
+void hpet_msi_unmask(struct irq_data *data)
 {
-	struct hpet_dev *hdev = get_irq_data(irq);
+	struct hpet_dev *hdev = data->handler_data;
 	unsigned int cfg;
 
 	/* unmask it */
@@ -451,10 +442,10 @@ void hpet_msi_unmask(unsigned int irq)
 	hpet_writel(cfg, HPET_Tn_CFG(hdev->num));
 }
 
-void hpet_msi_mask(unsigned int irq)
+void hpet_msi_mask(struct irq_data *data)
 {
+	struct hpet_dev *hdev = data->handler_data;
 	unsigned int cfg;
-	struct hpet_dev *hdev = get_irq_data(irq);
 
 	/* mask it */
 	cfg = hpet_readl(HPET_Tn_CFG(hdev->num));
@@ -462,18 +453,14 @@ void hpet_msi_mask(unsigned int irq)
 	hpet_writel(cfg, HPET_Tn_CFG(hdev->num));
 }
 
-void hpet_msi_write(unsigned int irq, struct msi_msg *msg)
+void hpet_msi_write(struct hpet_dev *hdev, struct msi_msg *msg)
 {
-	struct hpet_dev *hdev = get_irq_data(irq);
-
 	hpet_writel(msg->data, HPET_Tn_ROUTE(hdev->num));
 	hpet_writel(msg->address_lo, HPET_Tn_ROUTE(hdev->num) + 4);
 }
 
-void hpet_msi_read(unsigned int irq, struct msi_msg *msg)
+void hpet_msi_read(struct hpet_dev *hdev, struct msi_msg *msg)
 {
-	struct hpet_dev *hdev = get_irq_data(irq);
-
 	msg->data = hpet_readl(HPET_Tn_ROUTE(hdev->num));
 	msg->address_lo = hpet_readl(HPET_Tn_ROUTE(hdev->num) + 4);
 	msg->address_hi = 0;