lkml.org 
[lkml]   [2008]   [Jul]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH #upstream-fixes] ahci: give another shot at clearing all bits in irq_stat
Commit ea0c62f7cf70f13a67830471b613337bd0c9a62e 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: Tejun Heo <tj@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
---
The original report requires further investigation regarding why the
bogus change fixed the problem but this change is the correct thing to
do regardless.

Thanks.

drivers/ata/ahci.c | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index 061817a..5e6468a 100644
--- a/drivers/ata/ahci.c
+++ b/drivers/ata/ahci.c
@@ -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);

\
 
 \ /
  Last update: 2008-07-05 06:13    [W:0.043 / U:1.336 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site