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Commit d28f87aa authored by Tejun Heo's avatar Tejun Heo Committed by Linus Torvalds
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ahci: give another shot at clearing all bits in irq_stat 



Commit ea0c62f7 tried to clear all
bits in irq_stat but it didn't actually achieve that as irq_stat was
anded with port_map right after read.  This patch makes ahci driver
always use the unmasked value to clear irq_status.

While at it, add explanation on the peculiarities of ahci IRQ
clearing.

This was spotted by Linus Torvalds.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent d79df630

drivers/ata/ahci.c

+13 −3
Original line number Diff line number Diff line
@@ -1777,7 +1777,7 @@ static irqreturn_t ahci_interrupt(int irq, void *dev_instance) 
	struct ahci_host_priv *hpriv;

	unsigned int i, handled = 0;

	void __iomem *mmio;

	u32 irq_stat;

	u32 irq_stat, irq_masked;



	VPRINTK("ENTER\n");
@@ -1786,16 +1786,17 @@ static irqreturn_t ahci_interrupt(int irq, void *dev_instance) 


	/* sigh.  0xffffffff is a valid return from h/w */

	irq_stat = readl(mmio + HOST_IRQ_STAT);

	irq_stat &= hpriv->port_map;

	if (!irq_stat)

		return IRQ_NONE;



	irq_masked = irq_stat & hpriv->port_map;



	spin_lock(&host->lock);



	for (i = 0; i < host->n_ports; i++) {

		struct ata_port *ap;



		if (!(irq_stat & (1 << i)))

		if (!(irq_masked & (1 << i)))

			continue;



		ap = host->ports[i];
@@ -1812,6 +1813,15 @@ static irqreturn_t ahci_interrupt(int irq, void *dev_instance) 
		handled = 1;

	}



	/* HOST_IRQ_STAT behaves as level triggered latch meaning that

	 * it should be cleared after all the port events are cleared;

	 * otherwise, it will raise a spurious interrupt after each

	 * valid one.  Please read section 10.6.2 of ahci 1.1 for more

	 * information.

	 *

	 * Also, use the unmasked value to clear interrupt as spurious

	 * pending event on a dummy port might cause screaming IRQ.

	 */

	writel(irq_stat, mmio + HOST_IRQ_STAT);



	spin_unlock(&host->lock);