[SRU][Artful][OEM][PATCH] ALSA: hda - Force polling mode on CFL for fixing codec communication

[Hui Wang]

From: Takashi Iwai <tiwai at suse.de>

BugLink: https://bugs.launchpad.net/bugs/1758800

We've observed too long probe time with Coffee Lake (CFL) machines,
and the likely cause is some communication problem between the
HD-audio controller and the codec chips.  While the controller expects
an IRQ wakeup for each codec response, it seems sometimes missing, and
it takes one second for the controller driver to time out and read the
response in the polling mode.

Although we aren't sure about the real culprit yet, in this patch, we
put a workaround by forcing the polling mode as default for CFL
machines; the polling mode itself isn't too heavy, and much better
than other workarounds initially suggested (e.g. disabling
power-save), at least.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=199007
Fixes: e79b0006c45c ("ALSA: hda - Add Coffelake PCI ID")
Reported-and-tested-by: Hui Wang <hui.wang at canonical.com>
Cc: <stable at vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai at suse.de>
(cherry picked from commit a8d7bde23e7130686b76624b099f3e22dd38aef7)
Signed-off-by: Hui Wang <hui.wang at canonical.com>
---
 sound/pci/hda/hda_intel.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c
index 5ae8dda..f23db5f 100644
--- a/sound/pci/hda/hda_intel.c
+++ b/sound/pci/hda/hda_intel.c
@@ -371,6 +371,7 @@ enum {
 					((pci)->device == 0x160c))
 
 #define IS_BXT(pci) ((pci)->vendor == 0x8086 && (pci)->device == 0x5a98)
+#define IS_CFL(pci) ((pci)->vendor == 0x8086 && (pci)->device == 0xa348)
 
 static char *driver_short_names[] = {
 	[AZX_DRIVER_ICH] = "HDA Intel",
@@ -1740,6 +1741,10 @@ static int azx_create(struct snd_card *card, struct pci_dev *pci,
 	else
 		chip->bdl_pos_adj = bdl_pos_adj[dev];
 
+	/* Workaround for a communication error on CFL (bko#199007) */
+	if (IS_CFL(pci))
+		chip->polling_mode = 1;
+
 	err = azx_bus_init(chip, model[dev], &pci_hda_io_ops);
 	if (err < 0) {
 		kfree(hda);
-- 
2.7.4