x86, hpet: Add reference to chipset erratum documentation for disable-hpet-msi-quirk

[sfrench/cifs-2.6.git] / arch / x86 / kernel / quirks.c

diff --git a/arch/x86/kernel/quirks.c b/arch/x86/kernel/quirks.c
index 12e9feaa2f7aba947b65ca2fe3611be81321a8f1..e72d3fc6547d6fe767785e869deb90ea683d8cdc 100644 (file)
--- a/arch/x86/kernel/quirks.c
+++ b/arch/x86/kernel/quirks.c
@@ -495,10 +495,18 @@ void force_hpet_resume(void)
 /*
  * HPET MSI on some boards (ATI SB700/SB800) has side effect on
  * floppy DMA. Disable HPET MSI on such platforms.
+ * See erratum #27 (Misinterpreted MSI Requests May Result in
+ * Corrupted LPC DMA Data) in AMD Publication #46837,
+ * "SB700 Family Product Errata", Rev. 1.0, March 2010.
+ *
+ * Also force the read back of the CMP register in hpet_next_event()
+ * to work around the problem that the CMP register write seems to be
+ * delayed. See hpet_next_event() for details.
  */
 static void force_disable_hpet_msi(struct pci_dev *unused)
 {
        hpet_msi_disable = 1;
+       hpet_readback_cmp = 1;
 }
 
 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATI, PCI_DEVICE_ID_ATI_SBX00_SMBUS,