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

[Stefan Bader]

On 26.03.2018 08:37, Hui Wang wrote:
> 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>
Acked-by: Stefan Bader <stefan.bader at canonical.com>

> ---

Is this one needed in Bionic still or already included (either by 4.15 release
or stable update)?

>  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);
> 


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