From 194f2cdd0372587214157687648886ffeb601c1e Mon Sep 17 00:00:00 2001 From: Bard Liao Date: Wed, 25 Nov 2020 15:40:00 +0800 Subject: [PATCH 1/2] soundwire: bus: clear bus clash interrupt before the mask is enabled The SoundWire specification allows a Slave device to report a bus clash with the in-band interrupt mechanism when it detects a conflict while driving a bitSlot it owns. This can be a symptom of an electrical conflict or a programming error, and it's vital to detect reliably. Unfortunately, on some platforms, bus clashes are randomly reported by Slave devices after a bus reset, with an interrupt status set even before the bus clash interrupt is enabled. These initial spurious interrupts are not relevant and should optionally be filtered out, while leaving the interrupt mechanism enabled to detect 'true' issues. This patch suggests the addition of a Master level quirk to discard such interrupts. The quirk should in theory have been added at the Slave level, but since the problem was detected with different generations of Slave devices it's hard to point to a specific IP. The problem might also be board-dependent and hence dealing with a Master quirk is simpler. Signed-off-by: Bard Liao --- drivers/soundwire/bus.c | 10 ++++++++++ include/linux/soundwire/sdw.h | 4 ++++ 2 files changed, 14 insertions(+) diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c index 0900d184e8e228..3f174e49761442 100644 --- a/drivers/soundwire/bus.c +++ b/drivers/soundwire/bus.c @@ -1257,6 +1257,7 @@ static int sdw_slave_set_frequency(struct sdw_slave *slave) static int sdw_initialize_slave(struct sdw_slave *slave) { struct sdw_slave_prop *prop = &slave->prop; + int status; int ret; u8 val; @@ -1264,6 +1265,15 @@ static int sdw_initialize_slave(struct sdw_slave *slave) if (ret < 0) return ret; + if (slave->bus->prop.quirks & SDW_MASTER_QUIRKS_CLEAR_INITIAL_CLASH) { + /* Clear bus clash interrupt before enabling interrupt mask */ + status = sdw_read_no_pm(slave, SDW_SCP_INT1); + if (status & SDW_SCP_INT1_BUS_CLASH) { + dev_warn(&slave->dev, "Bus clash detected before INT mask is enabled\n"); + sdw_write_no_pm(slave, SDW_SCP_INT1, SDW_SCP_INT1_BUS_CLASH); + } + } + /* * Set SCP_INT1_MASK register, typically bus clash and * implementation-defined interrupt mask. The Parity detection diff --git a/include/linux/soundwire/sdw.h b/include/linux/soundwire/sdw.h index d08039d65825ef..c86902196bbc36 100644 --- a/include/linux/soundwire/sdw.h +++ b/include/linux/soundwire/sdw.h @@ -405,6 +405,7 @@ struct sdw_slave_prop { * command * @mclk_freq: clock reference passed to SoundWire Master, in Hz. * @hw_disabled: if true, the Master is not functional, typically due to pin-mux + * @quirks: bitmask identifying optional behavior beyond the scope of the MIPI specification */ struct sdw_master_prop { u32 revision; @@ -421,8 +422,11 @@ struct sdw_master_prop { u32 err_threshold; u32 mclk_freq; bool hw_disabled; + u32 quirks; }; +#define SDW_MASTER_QUIRKS_CLEAR_INITIAL_CLASH BIT(0) + int sdw_master_read_prop(struct sdw_bus *bus); int sdw_slave_read_prop(struct sdw_slave *slave); From 7a2abd8feed5faa27016e394cf63a0e757e1bbb3 Mon Sep 17 00:00:00 2001 From: Bard Liao Date: Tue, 1 Dec 2020 19:33:54 +0800 Subject: [PATCH 2/2] soundwire: intel: add SDW_MASTER_QUIRKS_CLEAR_INITIAL_CLASH quirk There is nothing we can do to handle the bus clash interrupt before interrupt mask is enabled. Signed-off-by: Bard Liao --- drivers/soundwire/intel.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/soundwire/intel.c b/drivers/soundwire/intel.c index 6a1e862b16c38c..b664cae9be260f 100644 --- a/drivers/soundwire/intel.c +++ b/drivers/soundwire/intel.c @@ -1286,6 +1286,8 @@ static int sdw_master_read_intel_prop(struct sdw_bus *bus) if (quirk_mask & SDW_INTEL_QUIRK_MASK_BUS_DISABLE) prop->hw_disabled = true; + prop->quirks = SDW_MASTER_QUIRKS_CLEAR_INITIAL_CLASH; + return 0; }