linux-kernel - Re: [PATCH V2 2/8] soundwire: amd: Add support for AMD Manager driver

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Date:   Tue, 14 Feb 2023 07:21:33 -0600
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     "Mukunda,Vijendar" <vijendar.mukunda@....com>, vkoul@...nel.org
Cc:     amadeuszx.slawinski@...ux.intel.com, Mario.Limonciello@....com,
        Sunil-kumar.Dommati@....com, Basavaraj.Hiregoudar@....com,
        Mastan.Katragadda@....com, Arungopal.kondaveeti@....com,
        Bard Liao <yung-chuan.liao@...ux.intel.com>,
        Sanyog Kale <sanyog.r.kale@...el.com>,
        open list <linux-kernel@...r.kernel.org>,
        "moderated list:SOUNDWIRE SUBSYSTEM" <alsa-devel@...a-project.org>
Subject: Re: [PATCH V2 2/8] soundwire: amd: Add support for AMD Manager driver


>>> +static void amd_sdw_probe_work(struct work_struct *work)
>>> +{
>>> +	struct amd_sdw_manager *amd_manager = container_of(work, struct amd_sdw_manager,
>>> +							   probe_work);
>>> +	struct sdw_master_prop *prop;
>>> +	int ret;
>>> +
>>> +	prop = &amd_manager->bus.prop;
>>> +	if (!prop->hw_disabled) {
>>> +		amd_enable_sdw_pads(amd_manager);
>>> +		ret = amd_init_sdw_manager(amd_manager);
>>> +		if (ret)
>>> +			return;
>>> +		amd_enable_sdw_interrupts(amd_manager);
>>> +		ret = amd_enable_sdw_manager(amd_manager);
>>> +		if (ret)
>>> +			return;
>>> +		amd_sdw_set_frameshape(amd_manager);
>>> +	}
>>> +}
>> There should be an explanation as to why you need a workqueue to
>> complete the probe.
> We want to separate the manager probe sequence and start up sequence.
> we will add the comment.

Do you need to split in two? For Intel, on some platforms we had a clear
power dependency, we had to wait until parts of the DSP were powered
before accessing SHIM registers, so we called the startup() when those
dependencies were resolved.

I am not sure you can count on the probe_work to enforce any kind of
delay, worst case the work function could be scheduled immediately.