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Wed, 11 Dec 2024 08:54:37 -0800 (PST) From: Bryan O'Donoghue Date: Wed, 11 Dec 2024 16:54:34 +0000 Subject: [PATCH v8 3/3] clk: qcom: Support attaching GDSCs to multiple parents Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20241211-b4-linux-next-24-11-18-clock-multiple-power-domains-v8-3-5d93cef910a4@linaro.org> References: <20241211-b4-linux-next-24-11-18-clock-multiple-power-domains-v8-0-5d93cef910a4@linaro.org> In-Reply-To: <20241211-b4-linux-next-24-11-18-clock-multiple-power-domains-v8-0-5d93cef910a4@linaro.org> To: Bjorn Andersson , Michael Turquette , Stephen Boyd , Dmitry Baryshkov Cc: linux-arm-msm@vger.kernel.org, linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org, Bryan O'Donoghue X-Mailer: b4 0.15-dev-355e8 When a clock-controller has multiple power-domains we need to attach the GDSCs provided by the clock-controller to each of the list of power-domains as power subdomains of each of the power-domains respectively. GDSCs come in three forms: 1. A GDSC which has no parent GDSC in the controller and no child GDSCs. 2. A GDSC which has no parent GDSC in the controller and has child GDSCs. 3. A child GDSC which derives power from the parent GDSC @ #2. Cases 1 and 2 are "top-level" GDSCs which depend on the power-domains - the power-rails attached to the clock-controller to power-on. When dtsi::power-domains =3D <> points to a single power-domain, Linux' platform probe code takes care of hooking up the referenced power-domains to the clock-controller. When dtsi::power-domains =3D <> points to more than one power-domain we must take responsibility to attach the list of power-domains to our clock-controller. An added complexity is that currently gdsc_enable() and gdsc_disable() do not register the top-level GDSCs as power subdomains of the controller's power-domains. This patch makes the subdomain association between whatever list of top-level GDSCs a clock-controller provides and the power-domain list of that clock-controller. What we don't do here is take responsibility to adjust the voltages on those power-rails when ramping clock frequencies - PLL rates - inside of the clock-controller. That voltage adjustment should be performed by operating-point/performance setpoint code in the driver requesting the new frequency. There are some questions that it is worth discussing in the commit log: 1. Should there be a hierarchy of power-domains in the clock-controller ? In other words if a list of dtsi::power-domains =3D should a specific hierarchy be applied to power pd_a then pd_b etc. It may be appropriate to introduce such a hierarchy however reasoning this point out some more, any hierarchy of power-domain dependencies should probably be handled in dtsi with a chain of power-domains. One power-domain provider would point to another via dtsi::power-domains =3D <>. For the case of GDSC on/off there is no clear use-case to implement a mechanism for a dependency list in the GDSC logic in-lieu of already existing methods to do dependencies in dtsi::power-domains =3D <>. A defacto ordering happens because the first power-domain pd_a will be powered before pd_b as the list of domains is iterated through linearly. This defacto hierarchical structure would not be reliable and should not be relied upon. If you need to have a hierarchy of power-domains then structuring the dependencies in the dtsi to Do this: pd_a { compat =3D "qcom, power-domain-a"; power-domains =3D <&pd_c>; }; pd_b { compat =3D "qcom, power-domain-b"; }; pd_c { compat =3D "qcom, power-domain-c"; }; clock-controller { compat =3D"qcom, some-clock-controller"; power-domains =3D <&pd_a, &pd_b>; } Not this: pd_a { compat =3D "qcom, power-domain-a"; }; pd_b { compat =3D "qcom, power-domain-b"; }; pd_c { compat =3D "qcom, power-domain-c"; }; clock-controller { compat =3D"qcom, some-clock-controller"; power-domains =3D <&pd_c, &pd_a, &pd_b>; } Thus ensuring that pd_a directly references its dependency to pd_c without assuming the order of references in clock-controller imparts or implements a deliberate and specific dependency hierarchy. 2. Should each GDSC inside a clock-controller be attached to each power-domain listed in dtsi::power-domains =3D <> ? In other words should child GDSCs attach to the power-domain list. The answer to this is no. GDSCs which are children of a GDSC within a clock-controller need only attach to the parent GDSC. With a single power-domain or a list of power-domains either way only the parent/top-level GDSC needs to be a subdomain of the input dtsi::power-domains =3D <>. 3. Should top-level GDSCs inside the clock-controller attach to each power-domain in the clock-controller. Yes a GDSC that has no parent GDSC inside of the clock-controller has an inferred dependency on the power-domains powering the clock-controller. 4. Performance states Right now the best information we have is that performance states should be applied to a power-domain list equally. Future implementations may have more detail to differentiate the option to vote for different voltages on different power-domains when setting clock frequencies. Either way setting the performance state of the power-domains for the clock-controller should be represented by operating-point code in the hardware driver which depends on the clocks not in the gdsc_enable()/gdsc_disable() path. Signed-off-by: Bryan O'Donoghue --- drivers/clk/qcom/common.c | 1 + drivers/clk/qcom/gdsc.c | 35 +++++++++++++++++++++++++++++++++++ drivers/clk/qcom/gdsc.h | 1 + 3 files changed, 37 insertions(+) diff --git a/drivers/clk/qcom/common.c b/drivers/clk/qcom/common.c index b79e6a73b53a4113ca324d102d7be5504a9fe85e..9e3380fd718198c9fe63d736161= 5a91c3ecb3d60 100644 --- a/drivers/clk/qcom/common.c +++ b/drivers/clk/qcom/common.c @@ -323,6 +323,7 @@ int qcom_cc_really_probe(struct device *dev, scd->dev =3D dev; scd->scs =3D desc->gdscs; scd->num =3D desc->num_gdscs; + scd->pd_list =3D cc->pd_list; ret =3D gdsc_register(scd, &reset->rcdev, regmap); if (ret) return ret; diff --git a/drivers/clk/qcom/gdsc.c b/drivers/clk/qcom/gdsc.c index 4fc6f957d0b846cc90e50ef243f23a7a27e66899..cb4afa6d584899f3dafa380d5e0= 1be6de9711737 100644 --- a/drivers/clk/qcom/gdsc.c +++ b/drivers/clk/qcom/gdsc.c @@ -506,6 +506,36 @@ static int gdsc_init(struct gdsc *sc) return ret; } =20 +static int gdsc_add_subdomain_list(struct dev_pm_domain_list *pd_list, + struct generic_pm_domain *subdomain) +{ + int i, ret; + + for (i =3D 0; i < pd_list->num_pds; i++) { + struct device *dev =3D pd_list->pd_devs[i]; + struct generic_pm_domain *genpd =3D pd_to_genpd(dev->pm_domain); + + ret =3D pm_genpd_add_subdomain(genpd, subdomain); + if (ret) + return ret; + } + + return 0; +} + +static void gdsc_remove_subdomain_list(struct dev_pm_domain_list *pd_list, + struct generic_pm_domain *subdomain) +{ + int i; + + for (i =3D 0; i < pd_list->num_pds; i++) { + struct device *dev =3D pd_list->pd_devs[i]; + struct generic_pm_domain *genpd =3D pd_to_genpd(dev->pm_domain); + + pm_genpd_remove_subdomain(genpd, subdomain); + } +} + int gdsc_register(struct gdsc_desc *desc, struct reset_controller_dev *rcdev, struct regmap *regmap) { @@ -558,6 +588,9 @@ int gdsc_register(struct gdsc_desc *desc, ret =3D pm_genpd_add_subdomain(scs[i]->parent, &scs[i]->pd); else if (!IS_ERR_OR_NULL(dev->pm_domain)) ret =3D pm_genpd_add_subdomain(pd_to_genpd(dev->pm_domain), &scs[i]->pd= ); + else if (desc->pd_list) + ret =3D gdsc_add_subdomain_list(desc->pd_list, &scs[i]->pd); + if (ret) return ret; } @@ -580,6 +613,8 @@ void gdsc_unregister(struct gdsc_desc *desc) pm_genpd_remove_subdomain(scs[i]->parent, &scs[i]->pd); else if (!IS_ERR_OR_NULL(dev->pm_domain)) pm_genpd_remove_subdomain(pd_to_genpd(dev->pm_domain), &scs[i]->pd); + else if (desc->pd_list) + gdsc_remove_subdomain_list(desc->pd_list, &scs[i]->pd); } of_genpd_del_provider(dev->of_node); } diff --git a/drivers/clk/qcom/gdsc.h b/drivers/clk/qcom/gdsc.h index 1e2779b823d1c8ca077c9b4cd0a0dbdf5f9457ef..dd843e86c05b2f30e6d9e978681= 580016333839d 100644 --- a/drivers/clk/qcom/gdsc.h +++ b/drivers/clk/qcom/gdsc.h @@ -80,6 +80,7 @@ struct gdsc_desc { struct device *dev; struct gdsc **scs; size_t num; + struct dev_pm_domain_list *pd_list; }; =20 #ifdef CONFIG_QCOM_GDSC --=20 2.45.2