Date:   Thu, 30 Sep 2021 06:21:36 +0000
From:   Ryan Lee <RyanS.Lee@...imintegrated.com>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Mark Brown <broonie@...nel.org>
CC:     "lgirdwood@...il.com" <lgirdwood@...il.com>,
        "perex@...ex.cz" <perex@...ex.cz>,
        "tiwai@...e.com" <tiwai@...e.com>,
        "yung-chuan.liao@...ux.intel.com" <yung-chuan.liao@...ux.intel.com>,
        "guennadi.liakhovetski@...ux.intel.com" 
        <guennadi.liakhovetski@...ux.intel.com>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "sathya.prakash.m.r@...el.com" <sathya.prakash.m.r@...el.com>,
        "ryan.lee.maxim@...il.com" <ryan.lee.maxim@...il.com>
Subject: RE: [EXTERNAL] Re: [PATCH] ASoC: max98373: Mark cache dirty before
 entering sleep

> >> Instead of changing the suspend sequence, can we please try to
> modify
> >> the
> >> max98373_io_init() routine to unconditionally flag the cache as
> >> dirty, maybe this points to a problem with the management of the
> >> max98373->first_hw_init flag.
> >
> > max98373_io_init() is not called because ' sdw_slave_status' remains
> '
> > SDW_SLAVE_ATTACHED' and 'max98373->hw_init' is already true.
> > Removing 'if (max98373->hw_init || status !=
> SDW_SLAVE_ATTACHED)'
> > condition in max98373_update_status() function instead of adding
> > regcache_mark_dirty() into max98373_suspend() can be an
> alternative way.
> > I think it is all about where regcache_mark_dirty() is called from.
> > The difference is that max98373_io_init() really do the software
> reset
> > and do amp initialization again which could be an overhead.
> 
> that description is aligned with my analysis that there's something very
> wrong happening here, it's not just a simple miss in the regmap
> handling but a major conceptual bug or misunderstanding in the way
> reset is handled.
> 
> First, there's the spec: on a reset initiated by the host or if the device
> loses sync for ANY reason, its status cannot remain ATTACHED.
> There's got to be a 16-frame period at least where the device has to
> monitor the sync pattern and cannot drive anything on the bus.
> 
> Then there's the hardware behavior on resume: on resume by default
> the Intel host will toggle the data pin for at least 4096 frames, which
> by spec means severe reset.
> 
> And last, there's the software init: we also force the status as
> UNATTACHED in drivers/soundwire/intel.c:
> 
>         /*
>          * make sure all Slaves are tagged as UNATTACHED and provide
>          * reason for reinitialization
>          */
>         sdw_clear_slave_status(bus,
> SDW_UNATTACH_REQUEST_MASTER_RESET);
> 
> But we've also seen the opposite effect of an amplifier reporting
> attached but losing sync immediately after the end of enumeration and
> never coming back on the bus, see issue
> https://nam02.safelinks.protection.outlook.com/?url=https%3A%2F%
> 2Fgithub.com%2Fthesofproject%2Flinux%2Fissues%2F3063&amp;data
> =04%7C01%7Cryans.lee%40maximintegrated.com%7Cb9f84a1267ec4
> f50b7a008d981edcc46%7Cfbd909dfea694788a554f24b7854ad03%7C0
> %7C0%7C637683680607026027%7CUnknown%7CTWFpbGZsb3d8eyJ
> WIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0
> %3D%7C1000&amp;sdata=rARkwTSB3DN%2BCYxGaehOhtCGEj1eLBl6
> Mk7QhynQSY8%3D&amp;reserved=0
> 
> In other words, we need to check what really happens on resume and
> why the amplifier keeps reporting its status as ATTACHED despite the
> spec requirements and software init, or loses this status after
> enumeration....Something really does not add-up, again it's not just a
> regmap management issue.
> 
> 
> 
I do not see #3063 issue on my side. No initialization failure or time-out has occurred.

Now I'm trying to solve the issue with max98373_io_init() function as suggested instead of adding
regmap_cache_dirty() in the suspend function.
max98373_io_init() was not called from max98373_update_status() when audio resume because
max98373->hw_init was 1 and Status was SDW_SLAVE_ATTACHED.
max98373_update_status() do not get SDW_SLAVE_UNATTACHED.
I confirmed that the issue could be resolved if SDW_SLAVE_UNATTACHED event arrives at
max98373_update_status() before SDW_SLAVE_ATTACHED is triggered.
Actually sdw_handle_slave_status() get SDW_SLAVE_UNATTACHED but this function exits at
https://github.com/thesofproject/linux/blob/topic/sof-dev/drivers/soundwire/bus.c#L1765
before reaching to https://github.com/thesofproject/linux/blob/topic/sof-dev/drivers/soundwire/bus.c#L1825
I'm not sure how to solve this issue because this code is commonly used for other Soundwire drivers as well.

I share the debug messages for the resume event as your reference.
[  127.490644] [DEBUG3] intel_resume_runtime
[  127.490655] [DEBUG3] intel_resume_runtime SDW_INTEL_CLK_STOP_BUS_RESET
[  127.490658] [DEBUG3] intel_init
[  127.490660] [DEBUG3] intel_link_power_up
[  127.490977] [DEBUG3] intel_resume_runtime SDW_UNATTACH_REQUEST_MASTER_RESET ..
[  127.490980] [DEBUG4] sdw_clear_slave_status request: 1
[  127.490983] [DEBUG4] sdw_modify_slave_status, ID:7, status: 0
[  127.490986] [DEBUG4] sdw_modify_slave_status, ID:3, status: 0
[  127.490994] [DEBUG3] intel_shim_wake wake_enable:0
[  127.491060] [DEBUG3] intel_shim_wake wake_enable:0
[  127.491191] [DEBUG] max98373_resume, first_hw_init: 1, unattach_request: 1
[  127.491194] [DEBUG] max98373_resume, INF MODE: 0
[  127.491953] [DEBUG4] sdw_handle_slave_status IN
[  127.491956] [DEBUG4] sdw_handle_slave_status, status[1] : 0, slave->status: 0, id:7	// UNATTACHED
[  127.491958] [DEBUG4] sdw_handle_slave_status, status[2] : 0, slave->status: 0, id:3
[  127.491960] [DEBUG4] sdw_handle_slave_status IN2 status[0] = 1
[  127.492808] [DEBUG4] sdw_handle_slave_status IN
[  127.492810] [DEBUG4] sdw_handle_slave_status, status[1] : 1, slave->status: 0, id:7	// ATTACHED
[  127.492812] [DEBUG4] sdw_handle_slave_status, status[2] : 1, slave->status: 0, id:3
[  127.492814] [DEBUG4] sdw_handle_slave_status IN2 status[0] = 0
[  127.492816] [DEBUG4] sdw_handle_slave_status IN3
[  127.492818] [DEBUG4] sdw_handle_slave_status status[1] = SDW_SLAVE_ATTACHED, slave->status : 0, slave:7, prev_status:0
[  127.492820] [DEBUG4] sdw_modify_slave_status, ID:7, status: 1
[  127.493008] [DEBUG4] sdw_update_slave_status update_status(1) IN slave:7
[  127.493010] [DEBUG4] sdw_update_slave_status update_status(1) OUT
[  127.493012] [DEBUG] max98373_update_status IN hw_init:1, status: 1, slave :7
[  127.493015] [DEBUG] max98373_update_status IN2 hw_init:1, max98373->first_hw_init: 1, status: 1
[  127.493017] [DEBUG4] sdw_handle_slave_status status[2] = SDW_SLAVE_ATTACHED, slave->status : 0, slave:3, prev_status:0
[  127.493019] [DEBUG4] sdw_modify_slave_status, ID:3, status: 1
[  127.493199] [DEBUG4] sdw_update_slave_status update_status(1) IN slave:3
[  127.493201] [DEBUG4] sdw_update_slave_status update_status(1) OUT
[  127.493204] [DEBUG] max98373_update_status IN hw_init:1, status: 1, slave :3
[  127.493207] [DEBUG] max98373_update_status IN2 hw_init:1, max98373->first_hw_init: 1, status: 1

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