[alsa-devel] [PATCH 2/2] ALSA: hda - Increase default bdl_pos_adj for Baytrail/Braswell

[Takashi Iwai]

Intel Atom processors seem to have a problem at recording when
bdl_pos_adj is set to an odd value.  Actually, for the old Atoms, we
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 at henneberg-systemdesign.com>
Signed-off-by: Takashi Iwai <tiwai at suse.de>
---
 sound/pci/hda/hda_intel.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c
index a17bf0467edc..56ef6b6fb546 100644
--- 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:
-- 
2.6.4