On 26-01-21, 16:37, Bard Liao wrote:
> 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 <yung-chuan.liao@xxxxxxxxxxxxxxx>
> Reviewed-by: Rander Wang <rander.wang@xxxxxxxxxxxxxxx>
> Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx>
> ---
> 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 6e1c988f3845..d394905936e4 100644
> --- a/drivers/soundwire/bus.c
> +++ b/drivers/soundwire/bus.c
> @@ -1240,6 +1240,7 @@ 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;
>
> @@ -1247,6 +1248,15 @@ 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 f0b01b728640..a2766c3b603d 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;
Can we do u64 here please.. I dont know where we would end up.. but
would hate if we start running out of space ..
> };
>
> +#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);
>
> --
> 2.17.1
--
~Vinod
