From: "Martin Povišer" <povik+lin@cutebit.org>
To: Mark Brown <broonie@kernel.org>
Cc: devicetree@vger.kernel.org, alsa-devel@alsa-project.org,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
Sven Peter <sven@svenpeter.dev>, Hector Martin <marcan@marcan.st>,
Liam Girdwood <lgirdwood@gmail.com>,
linux-kernel@vger.kernel.org, Rob Herring <robh+dt@kernel.org>,
asahi@lists.linux.dev, Philipp Zabel <p.zabel@pengutronix.de>,
Alyssa Rosenzweig <alyssa@rosenzweig.io>
Subject: Re: [PATCH v2 3/4] ASoC: apple: mca: Start new platform driver
Date: Tue, 23 Aug 2022 13:51:35 +0200 [thread overview]
Message-ID: <6C89CA60-D0E2-4869-B21C-17AD4AA1974C@cutebit.org> (raw)
In-Reply-To: <YwS6lHeGH0BZKHeB@sirena.org.uk>
> On 23. 8. 2022, at 13:31, Mark Brown <broonie@kernel.org> wrote:
>
> On Tue, Aug 23, 2022 at 09:33:36AM +0200, Martin Povišer wrote:
>>> On 22. 8. 2022, at 19:39, Mark Brown <broonie@kernel.org> wrote:
>>> On Fri, Aug 19, 2022 at 02:54:29PM +0200, Martin Povišer wrote:
>>>> + /*
>>>> + * We can't power up the device earlier than this because
>>>> + * the power state driver would error out on seeing the device
>>>> + * as clock-gated.
>>>> + */
>>>> + cl->pd_link = device_link_add(mca->dev, cl->pd_dev,
>>>> + DL_FLAG_STATELESS | DL_FLAG_PM_RUNTIME |
>>>> + DL_FLAG_RPM_ACTIVE);
>
>>> I'm not clear on this dynamically adding and removing device links stuff
>>> - it looks like the main (only?) purpose is to take a runtime PM
>>> reference to the target device which is fine but it's not clear why
>>> device links are involved given that the links are created and destroyed
>>> every time the DAI is used, AFAICT always in the same fixed
>>> relationship. It's not a problem, it's just unclear.
>
>> Indeed the only purpose is powering up the cluster’s power domain (there’s
>> one domain for each cluster). Adding the links is the only way I know to
>> do it. They need to be added dynamically (as opposed to statically linking,
>> say, the DAI’s ->dev to the cluster’s ->pd_dev, which I guess may do
>> something similar), because we need to sequence the power-up/power-down
>> with the enablement of the clocks.
>
> You could also just do the underlying runtime power management
> operations directly couldn't you? It's not clear what the device link
> stuff is adding.
This seems to be the way to do it. Quoting from documentation of
dev_pm_domain_attach_by_id, by which we obtain the mca->dev and cl->pd_dev
the link is between:
* This function should typically be invoked by a driver during the probe phase,
* in case its device requires power management through multiple PM domains. The
* driver may benefit from using the received device, to configure device-links
* towards its original device. Depending on the use-case and if needed, the
* links may be dynamically changed by the driver, which allows it to control
* the power to the PM domains independently from each other.
--
Martin
WARNING: multiple messages have this Message-ID (diff)
From: "Martin Povišer" <povik+lin@cutebit.org>
To: Mark Brown <broonie@kernel.org>
Cc: Liam Girdwood <lgirdwood@gmail.com>,
Rob Herring <robh+dt@kernel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
Hector Martin <marcan@marcan.st>, Sven Peter <sven@svenpeter.dev>,
Philipp Zabel <p.zabel@pengutronix.de>,
Alyssa Rosenzweig <alyssa@rosenzweig.io>,
asahi@lists.linux.dev, alsa-devel@alsa-project.org,
devicetree@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 3/4] ASoC: apple: mca: Start new platform driver
Date: Tue, 23 Aug 2022 13:51:35 +0200 [thread overview]
Message-ID: <6C89CA60-D0E2-4869-B21C-17AD4AA1974C@cutebit.org> (raw)
In-Reply-To: <YwS6lHeGH0BZKHeB@sirena.org.uk>
> On 23. 8. 2022, at 13:31, Mark Brown <broonie@kernel.org> wrote:
>
> On Tue, Aug 23, 2022 at 09:33:36AM +0200, Martin Povišer wrote:
>>> On 22. 8. 2022, at 19:39, Mark Brown <broonie@kernel.org> wrote:
>>> On Fri, Aug 19, 2022 at 02:54:29PM +0200, Martin Povišer wrote:
>>>> + /*
>>>> + * We can't power up the device earlier than this because
>>>> + * the power state driver would error out on seeing the device
>>>> + * as clock-gated.
>>>> + */
>>>> + cl->pd_link = device_link_add(mca->dev, cl->pd_dev,
>>>> + DL_FLAG_STATELESS | DL_FLAG_PM_RUNTIME |
>>>> + DL_FLAG_RPM_ACTIVE);
>
>>> I'm not clear on this dynamically adding and removing device links stuff
>>> - it looks like the main (only?) purpose is to take a runtime PM
>>> reference to the target device which is fine but it's not clear why
>>> device links are involved given that the links are created and destroyed
>>> every time the DAI is used, AFAICT always in the same fixed
>>> relationship. It's not a problem, it's just unclear.
>
>> Indeed the only purpose is powering up the cluster’s power domain (there’s
>> one domain for each cluster). Adding the links is the only way I know to
>> do it. They need to be added dynamically (as opposed to statically linking,
>> say, the DAI’s ->dev to the cluster’s ->pd_dev, which I guess may do
>> something similar), because we need to sequence the power-up/power-down
>> with the enablement of the clocks.
>
> You could also just do the underlying runtime power management
> operations directly couldn't you? It's not clear what the device link
> stuff is adding.
This seems to be the way to do it. Quoting from documentation of
dev_pm_domain_attach_by_id, by which we obtain the mca->dev and cl->pd_dev
the link is between:
* This function should typically be invoked by a driver during the probe phase,
* in case its device requires power management through multiple PM domains. The
* driver may benefit from using the received device, to configure device-links
* towards its original device. Depending on the use-case and if needed, the
* links may be dynamically changed by the driver, which allows it to control
* the power to the PM domains independently from each other.
--
Martin
next prev parent reply other threads:[~2022-08-23 11:52 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-19 12:54 [PATCH v2 0/4] ASoC platform driver for Apple MCA Martin Povišer
2022-08-19 12:54 ` Martin Povišer
2022-08-19 12:54 ` [PATCH v2 1/4] dt-bindings: sound: Add Apple MCA I2S transceiver Martin Povišer
2022-08-19 12:54 ` Martin Povišer
2022-08-19 12:58 ` Martin Povišer
2022-08-19 12:58 ` Martin Povišer
2022-08-19 13:08 ` Krzysztof Kozlowski
2022-08-19 13:08 ` Krzysztof Kozlowski
2022-08-19 13:09 ` Krzysztof Kozlowski
2022-08-19 13:09 ` Krzysztof Kozlowski
2022-08-19 14:14 ` Martin Povišer
2022-08-19 14:14 ` Martin Povišer
2022-08-19 14:17 ` Krzysztof Kozlowski
2022-08-19 14:17 ` Krzysztof Kozlowski
2022-08-22 18:59 ` Rob Herring
2022-08-22 18:59 ` Rob Herring
2022-08-19 12:54 ` [PATCH v2 2/4] arm64: dts: apple: t8103: Add MCA and its support Martin Povišer
2022-08-19 12:54 ` Martin Povišer
2022-08-19 13:12 ` Krzysztof Kozlowski
2022-08-19 13:12 ` Krzysztof Kozlowski
2022-08-19 14:24 ` Martin Povišer
2022-08-19 14:24 ` Martin Povišer
2022-08-23 11:02 ` Krzysztof Kozlowski
2022-08-23 11:02 ` Krzysztof Kozlowski
2022-08-19 12:54 ` [PATCH v2 3/4] ASoC: apple: mca: Start new platform driver Martin Povišer
2022-08-19 12:54 ` Martin Povišer
2022-08-22 17:39 ` Mark Brown
2022-08-22 17:39 ` Mark Brown
2022-08-23 7:33 ` Martin Povišer
2022-08-23 7:33 ` Martin Povišer
2022-08-23 11:31 ` Mark Brown
2022-08-23 11:31 ` Mark Brown
2022-08-23 11:51 ` Martin Povišer [this message]
2022-08-23 11:51 ` Martin Povišer
2022-08-23 11:53 ` Martin Povišer
2022-08-23 11:53 ` Martin Povišer
2022-08-19 12:54 ` [PATCH v2 4/4] ASoC: apple: mca: Add locks on foreign cluster access Martin Povišer
2022-08-19 12:54 ` Martin Povišer
2022-08-22 17:45 ` Mark Brown
2022-08-22 17:45 ` Mark Brown
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