linux-kernel - Re: [PATCH v2 1/3] soundwire: add master quirks for bus clash and parity

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Date:   Mon, 22 Mar 2021 17:37:17 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Bard Liao <yung-chuan.liao@...ux.intel.com>
Cc:     alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        gregkh@...uxfoundation.org, srinivas.kandagatla@...aro.org,
        rander.wang@...ux.intel.com, hui.wang@...onical.com,
        pierre-louis.bossart@...ux.intel.com, sanyog.r.kale@...el.com,
        bard.liao@...el.com
Subject: Re: [PATCH v2 1/3] soundwire: add master quirks for bus clash and
 parity

On 02-03-21, 16:27, Bard Liao wrote:
> Currently quirks are only allowed for Slave devices. This patch
> describes the need for two quirks at the Master level.
> 
> a) bus clash
> 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.
> 
> b) parity
> 
> Additional tests on a new platform with the Maxim 98373 amplifier
> showed a rare case where the parity interrupt is also thrown on
> startup, at the same time as bus clashes. This issue only seems to
> happen infrequently and was only observed during suspend-resume stress
> tests while audio is streaming. We could make the problem go away by
> adding a Slave-level quirk, but there is no evidence that the issue is
> actually a Slave problem: the parity is provided by the Master, which
> could also set an invalid parity in corner cases.
> 
> BugLink: https://github.com/thesofproject/linux/issues/2578
> BugLink: https://github.com/thesofproject/linux/issues/2533
> 

Please do not add blank lines here

> Co-developed-by: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
> Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
> Signed-off-by: Bard Liao <yung-chuan.liao@...ux.intel.com>
> Reviewed-by: Guennadi Liakhovetski <guennadi.liakhovetski@...ux.intel.com>
> ---
>  include/linux/soundwire/sdw.h | 22 ++++++++++++++++++++++
>  1 file changed, 22 insertions(+)
> 
> diff --git a/include/linux/soundwire/sdw.h b/include/linux/soundwire/sdw.h
> index d08039d65825..25f2a14e2e83 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 +422,29 @@ struct sdw_master_prop {
>  	u32 err_threshold;
>  	u32 mclk_freq;
>  	bool hw_disabled;
> +	u64 quirks;
>  };
>  
> +/* Definitions for Master quirks */
> +
> +/*
> + * In a number of platforms bus clashes are reported after a hardware
> + * reset but without any explanations or evidence of a real problem.
> + * The following quirk will discard all initial bus clash interrupts
> + * but will leave the detection on should real bus clashes happen
> + */
> +#define SDW_MASTER_QUIRKS_CLEAR_INITIAL_CLASH	BIT(0)
> +
> +/*
> + * Some Slave devices have known issues with incorrect parity errors
> + * reported after a hardware reset. However during integration unexplained
> + * parity errors can be reported by Slave devices, possibly due to electrical
> + * issues at the Master level.
> + * The following quirk will discard all initial parity errors but will leave
> + * the detection on should real parity errors happen.
> + */
> +#define SDW_MASTER_QUIRKS_CLEAR_INITIAL_PARITY	BIT(1)
> +
>  int sdw_master_read_prop(struct sdw_bus *bus);
>  int sdw_slave_read_prop(struct sdw_slave *slave);
>  
> -- 
> 2.17.1

-- 
~Vinod