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soundwire: intel_auxdevice: add kernel parameter for mclk divider

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Add a kernel parameter to work-around discrepancies between hardware
and platform firmware, it's not unusual to see e.g. 38.4MHz listed in
_DSD properties as the SoundWire clock source, but the hardware may be
based on a 19.2 MHz mclk source.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Link: https://lore.kernel.org/r/20241004021850.9758-1-yung-chuan.liao@linux.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
This commit is contained in:
Pierre-Louis Bossart 2024-10-04 10:18:50 +08:00 committed by Vinod Koul
parent 71b405b184
commit cbcb7edd09
3 changed files with 15 additions and 2 deletions
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1
Documentation/admin-guide/kernel-parameters.rst
View File

@ -159,6 +159,7 @@ is applicable::
SCSI Appropriate SCSI support is enabled.
A lot of drivers have their options described inside
the Documentation/scsi/ sub-directory.
SDW SoundWire support is enabled.
SECURITY Different security models are enabled.
SELINUX SELinux support is enabled.
SERIAL Serial support is enabled.

4
Documentation/admin-guide/kernel-parameters.txt
View File

@ -6060,6 +6060,10 @@
non-zero "wait" parameter. See weight_single
and weight_many.
sdw_mclk_divider=[SDW]
Specify the MCLK divider for Intel SoundWire buses in
case the BIOS does not provide the clock rate properly.
skew_tick= [KNL,EARLY] Offset the periodic timer tick per cpu to mitigate
xtime_lock contention on larger systems, and/or RCU lock
contention on all systems with CONFIG_MAXSMP set.

12
drivers/soundwire/intel_auxdevice.c
View File

@ -41,6 +41,10 @@ static int md_flags;
module_param_named(sdw_md_flags, md_flags, int, 0444);
MODULE_PARM_DESC(sdw_md_flags, "SoundWire Intel Master device flags (0x0 all off)");
static int mclk_divider;
module_param_named(sdw_mclk_divider, mclk_divider, int, 0444);
MODULE_PARM_DESC(sdw_mclk_divider, "SoundWire Intel mclk divider");
struct wake_capable_part {
const u16 mfg_id;
const u16 part_id;
@ -142,8 +146,12 @@ static int sdw_master_read_intel_prop(struct sdw_bus *bus)
"intel-sdw-ip-clock",
&prop->mclk_freq);
/* the values reported by BIOS are the 2x clock, not the bus clock */
prop->mclk_freq /= 2;
if (mclk_divider)
/* use kernel parameter for BIOS or board work-arounds */
prop->mclk_freq /= mclk_divider;
else
/* the values reported by BIOS are the 2x clock, not the bus clock */
prop->mclk_freq /= 2;
fwnode_property_read_u32(link,
"intel-quirk-mask",