ALSA: hda - Increase default bdl_pos_adj for Baytrail/Braswell

Intel Atom processors seem to have a problem at recording when
bdl_pos_adj is set to an odd value.  When a value like 1 is used, it
may drop the samples unexpectedly.  Actually, for the old Atoms, we
used to set AZX_DRIVER_SCH type, and this assigns 32 as default.
Meanwhile the newer chips, Baytrail and Braswell, are set as
AZX_DRIVER_PCH, and the lower default value, 1, is assigned.

This patch changes the default values for these chipsets to a safer
default, 32, again.  Since changing the driver type (AZX_DRIVER_XXX)
leads to the rename of the driver string, it would result in a
possible regression.  So, we can't change the type.  Instead, in this
patch, manual (ugly) PCI ID checks are added on top.

A drawback by this increase is the slight increase of the latency, but
it's a sub-ms order in normal situations, so mostly negligible.

Reported-and-tested-by: Jochen Henneberg <jh@henneberg-systemdesign.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c
index a17bf04..56ef6b6 100644 (file)
--- a/sound/pci/hda/hda_intel.c
+++ b/sound/pci/hda/hda_intel.c
@@ -1490,6 +1490,15 @@ static void azx_probe_work(struct work_struct *work)
 
 static int default_bdl_pos_adj(struct azx *chip)
 {
+       /* some exceptions: Atoms seem problematic with value 1 */
+       if (chip->pci->vendor == PCI_VENDOR_ID_INTEL) {
+               switch (chip->pci->device) {
+               case 0x0f04: /* Baytrail */
+               case 0x2284: /* Braswell */
+                       return 32;
+               }
+       }
+
        switch (chip->driver_type) {
        case AZX_DRIVER_ICH:
        case AZX_DRIVER_PCH: