linux-kernel - Re: [PATCH 06/10] mfd: cs42l43: Add support for cs42l43 core driver

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Message-ID: <650012a3-b455-8be5-fd6d-d0775e718e6a@linux.intel.com>
Date:   Thu, 18 May 2023 10:16:16 -0500
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Charles Keepax <ckeepax@...nsource.cirrus.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     broonie@...nel.org, lee@...nel.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        tglx@...utronix.de, maz@...nel.org, linus.walleij@...aro.org,
        vkoul@...nel.org, lgirdwood@...il.com,
        yung-chuan.liao@...ux.intel.com, sanyog.r.kale@...el.com,
        alsa-devel@...a-project.org, patches@...nsource.cirrus.com,
        devicetree@...r.kernel.org, linux-gpio@...r.kernel.org,
        linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 06/10] mfd: cs42l43: Add support for cs42l43 core driver


>>> +	ret = regmap_register_patch(cs42l43->regmap, cs42l43_reva_patch,
>>> +				    ARRAY_SIZE(cs42l43_reva_patch));
>>> +	if (ret) {
>>> +		dev_err(cs42l43->dev, "Failed to apply register patch: %d\n", ret);
>>> +		goto err;
>>> +	}
>>> +
>>> +	pm_runtime_mark_last_busy(cs42l43->dev);
>>> +	pm_runtime_put_autosuspend(cs42l43->dev);
>>> +
>>> +	ret = devm_mfd_add_devices(cs42l43->dev, PLATFORM_DEVID_NONE,
>>> +				   cs42l43_devs, ARRAY_SIZE(cs42l43_devs),
>>
>> I don't why adding devices is not in probe. They use the same regmap
>> right? So there will be no problem in probing them from MFD probe.
> 
> Well except SoundWire is a bit of a special boy, the hardware is
> not necessarily available in probe, the hardware is only available
> at some point later when the device attaches. Doing it this way all
> of the attaching (and various detach/attach cycles the device needs
> during configuration) are over by the time the child drivers bind, so
> they don't all need special code to handle that.

if the devices are added in the probe, then the regmap needs to be moved
to cache-only and another special API would be needed to tell the MFD
framework to turn the regmap cache-only off.

But if it's the same regmap, the regmap cache is handled in the
SoundWire update_status callback so maybe  Krzysztof's proposal does work?