linux-kernel - Re: [PATCH 01/19] ASoC: amd: ps: create platform devices based on acp config

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Date:   Tue, 31 Jan 2023 10:00:54 -0600
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     "Mukunda,Vijendar" <vijendar.mukunda@....com>, broonie@...nel.org,
        vkoul@...nel.org, alsa-devel@...a-project.org
Cc:     Mastan.Katragadda@....com, Sunil-kumar.Dommati@....com,
        open list <linux-kernel@...r.kernel.org>,
        Basavaraj.Hiregoudar@....com, Takashi Iwai <tiwai@...e.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Mario.Limonciello@....com, arungopal.kondaveeti@....com,
        Sanyog Kale <sanyog.r.kale@...el.com>,
        Bard Liao <yung-chuan.liao@...ux.intel.com>,
        Syed Saba Kareem <Syed.SabaKareem@....com>
Subject: Re: [PATCH 01/19] ASoC: amd: ps: create platform devices based on acp
 config



On 1/31/23 07:09, Mukunda,Vijendar wrote:
> On 16/01/23 13:32, Mukunda,Vijendar wrote:
>> On 13/01/23 22:41, Pierre-Louis Bossart wrote:
>>>>>> +		if (is_dmic_dev && is_sdw_dev) {
>>>>>> +			switch (acp_data->sdw_master_count) {
>>>>>> +			case 1:
>>>>>> +				acp_data->pdev_mask = ACP63_SDW_PDM_DEV_MASK;
>>>>>> +				acp_data->pdev_count = ACP63_SDW0_PDM_MODE_DEVS;
>>>>>> +				break;
>>>>>> +			case 2:
>>>>>> +				acp_data->pdev_mask = ACP63_SDW_PDM_DEV_MASK;
>>>>>> +				acp_data->pdev_count = ACP63_SDW0_SDW1_PDM_MODE_DEVS;
>>>>>> +				break;
>>>>> so the cover letter is indeed wrong and confuses two controllers for two
>>>>> managers.
>>>> ACP IP has two independent manager instances driven by separate controller
>>>> each which are connected in different power domains.
>>>>
>>>> we should create two separate ACPI companion devices for separate
>>>> manager instance.  Currently we have limitations with BIOS.
>>>> we are going with single ACPI companion device.
>>>> We will update the changes later.
>>> Humm, this is tricky. The BIOS interface isn't something that can be
>>> changed at will on the kernel side, you'd have to maintain two solutions
>>> with a means to detect which one to use.
>>>
>>> Or is this is a temporary issue on development devices, then that part
>>> should probably not be upstreamed.
>> It's a temporary issue on development devices.
>> We had discussion with Windows dev team and BIOS team.
>> They have agreed to modify ACPI companion device logic.
>> We will update the two companion devices logic for two manager
>> instances in V2 version.
> After experimenting, two ACPI companion devices approach,
> we got an update from Windows team, there is a limitation
> on windows stack. For current platform, we can't proceed
> with two ACPI companion devices.

so how would the two controllers be declared then in the DSDT used by
Windows? There's a contradiction between having a single companion
device and the ability to set the 'manager-number' to one.

You probably want to give an example of what you have, otherwise we
probably will talk past each other.
> 
> Even on Linux side, if we create two ACPI companion devices
> followed by creating a single soundwire manager instance per
> Soundwire controller, we have observed an issue in a scenario,
> where similar codec parts(UID are also same) are connected on
> both soundwire manager instances.

We've been handling this case of two identical amplifiers on two
different links for the last 3 years. I don't see how this could be a
problem, the codecs are declared in the scope of the companion device
and the _ADR defines in bits [51..48] which link the codec is connected to.

see example below from a TigerLake device with two identical amsp on
link 1 and 2.

   Scope (_SB.PC00.HDAS.SNDW)
    {
       Device (SWD1)
        {
            Name (_ADR, 0x000131025D131601)  // _ADR: Address

	Device (SWD2)
        {
            Name (_ADR, 0x000230025D131601)  // _ADR: Address

> As per MIPI Disco spec, for single link controllers Link ID should
> be set to zero.
> If we use Link ID as zero, for the soundwire manager which is on
> the second soundwire controller ACPI device scope, then soundwire
> framework is not allowing to create peripheral device node as its
> duplicate one.

I still don't see how it's possible. There is an IDA used in the bus
allocation

static int sdw_get_id(struct sdw_bus *bus)
{
	int rc = ida_alloc(&sdw_bus_ida, GFP_KERNEL);

	if (rc < 0)
		return rc;

	bus->id = rc;
	return 0;
}

and that's used for debugfs

	/* create the debugfs master-N */
	snprintf(name, sizeof(name), "master-%d-%d", bus->id, bus->link_id);

as well as in sdw_master_device_add():
	dev_set_name(&md->dev, "sdw-master-%d", bus->id);

can you clarify what part of the 'SoundWire framework' is problematic? I
guess the problem is that you have identical devices with the same _ADR
under the same manager, which is problematic indeed, but that's not a
SoundWire framework issue, just not a supported configuration.

> If we want to support two ACPI companion device approach
> on our future platforms, how to proceed?

Well how about dealing with a single companion device first, cause
that's what you have now and that's already problematic.