Patch "ALSA: hda - Force polling mode on CFL for fixing codec communication" has been added to the 4.15-stable tree

This is a note to let you know that I've just added the patch titled

ALSA: hda - Force polling mode on CFL for fixing codec communication

to the 4.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
alsa-hda-force-polling-mode-on-cfl-for-fixing-codec-communication.patch
and it can be found in the queue-4.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Takashi Iwai <[email protected]>
Date: Wed, 21 Mar 2018 10:06:13 +0100
Subject: ALSA: hda - Force polling mode on CFL for fixing codec communication

From: Takashi Iwai <[email protected]>

commit a8d7bde23e7130686b76624b099f3e22dd38aef7 upstream.

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

---
 sound/pci/hda/hda_intel.c |    5 +++++
 1 file changed, 5 insertions(+)

@@ -375,6 +375,7 @@ 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",

@@ -1744,6 +1745,10 @@ static int azx_create(struct snd_card *c
 	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);

Patches currently in stable-queue which might be from [email protected] are

queue-4.15/alsa-aloop-fix-access-to-not-yet-ready-substream-via-cable.patch queue-4.15/alsa-hda-realtek-fix-speaker-no-sound-after-system-resume.patch queue-4.15/alsa-hda-realtek-fix-dell-headset-mic-can-t-record.patch queue-4.15/alsa-hda-realtek-always-immediately-update-mute-led-with-pin-vref.patch queue-4.15/alsa-usb-audio-fix-parsing-descriptor-of-uac2-processing-unit.patch queue-4.15/alsa-aloop-sync-stale-timer-before-release.patch queue-4.15/alsa-hda-force-polling-mode-on-cfl-for-fixing-codec-communication.patch