Re: New MSI support in sata_sil24 still broken in 2.6.33-rc3

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On 01/06/2010 03:37 AM, Torsten Kaiser wrote:
After activating the MSI support by adding sata_sil24.msi=1 to the
kernel command line, the first write to a drive attached to the SiI
3132 controller results in the following errors:

[  138.950074] ata2.00: exception Emask 0x0 SAct 0xf SErr 0x0 action 0x6 frozen
[  138.961023] ata2.00: failed command: WRITE FPDMA QUEUED
[  138.970034] ata2.00: cmd 61/00:00:a5:95:4a/04:00:01:00:00/40 tag 0
ncq 524288 out
[  138.970037]          res 40/00:00:00:00:00/00:00:00:00:00/00 Emask
0x4 (timeout)

Looking at the code in sata_sil24 and the SiI3132 datasheet, there's a control bit which doesn't seem to be handled in the driver, global control register bit 30: "MSI Acknowledge (W). Writing a one to this bit acknowledges a Message Signaled Interrupt and permits generation of another MSI. This bit is cleared immediately after the acknowledgement is recognized by the control logic, hence the bit will always be read as a zero. If all interrupt conditions are removed subsequent to an MSI, it is not necessary to assert this Acknowledge; another MSI will be generated when an interrupt condition occurs."

The way the interrupt handler for this driver works is that we check the global IRQ status register, and then based on what ports indicated an interrupt in that register, we check the individual port command completion registers. The issue would seem to be that if a port got an interrupt condition in between these two operations, we'd miss it, and the MSI logic described above then wouldn't generate any more interrupts since we didn't remove all interrupt conditions.

Can you try this patch and see if it helps? (Might be whitespace damaged but hopefully you can apply manually in that case.)

diff --git a/drivers/ata/sata_sil24.c b/drivers/ata/sata_sil24.c
index 1370df6..d3d8dec 100644
--- a/drivers/ata/sata_sil24.c
+++ b/drivers/ata/sata_sil24.c
@@ -102,6 +102,7 @@ enum {
        HOST_CTRL_STOP          = (1 << 18), /* latched PCI STOP */
        HOST_CTRL_DEVSEL        = (1 << 19), /* latched PCI DEVSEL */
        HOST_CTRL_REQ64         = (1 << 20), /* latched PCI REQ64 */
+       HOST_CTRL_MSIACK        = (1 << 30), /* MSI acknowledge */
        HOST_CTRL_GLOBAL_RST    = (1 << 31), /* global reset */

        /*
@@ -1168,6 +1169,7 @@ static irqreturn_t sil24_interrupt(int irq, void *dev_instance) ": interrupt from disabled port %d\n", i);
                }

+       writel(IRQ_STAT_4PORTS | HOST_CTRL_MSIACK, host_base + HOST_CTRL);
        spin_unlock(&host->lock);
  out:
        return IRQ_RETVAL(handled);
--
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