Re: [PATCH v2 2/3] cpufreq: qcom-nvmem: Enable virtual power domain devices

On Wed, 18 Oct 2023 at 10:06, Stephan Gerhold stephan.gerhold@kernkonzept.com wrote:

The genpd core caches performance state votes from devices that are runtime suspended as of commit 3c5a272202c2 ("PM: domains: Improve runtime PM performance state handling"). They get applied once the device becomes active again.

To attach the power domains needed by qcom-cpufreq-nvmem the OPP core calls genpd_dev_pm_attach_by_id(). This results in "virtual" dummy devices that use runtime PM only to control the enable and performance state for the attached power domain.

However, at the moment nothing ever resumes the virtual devices created for qcom-cpufreq-nvmem. They remain permanently runtime suspended. This means that performance state votes made during cpufreq scaling get always cached and never applied to the hardware.

Fix this by enabling the devices after attaching them and use dev_pm_syscore_device() to ensure the power domains also stay on when going to suspend. Since it supplies the CPU we can never turn it off from Linux. There are other mechanisms to turn it off when needed, usually in the RPM firmware (RPMPD) or the cpuidle path (CPR genpd).

I believe we discussed using dev_pm_syscore_device() for the previous version. It's not intended to be used for things like the above.

Moreover, I was under the impression that it wasn't really needed. In fact, I would think that this actually breaks things for system suspend/resume, as in this case the cpr driver's genpd ->power_on|off() callbacks are no longer getting called due this, which means that the cpr state machine isn't going to be restored properly. Or did I get this wrong?

Kind regards Uffe

Without this fix performance states votes are silently ignored, and the CPU/CPR voltage is never adjusted. This has been broken since 5.14 but for some reason no one noticed this on QCS404 so far.

Cc: stable@vger.kernel.org Fixes: 1cb8339ca225 ("cpufreq: qcom: Add support for qcs404 on nvmem driver") Signed-off-by: Stephan Gerhold stephan.gerhold@kernkonzept.com

---

drivers/cpufreq/qcom-cpufreq-nvmem.c | 49 +++++++++++++++++++++++++++++++++--- 1 file changed, 46 insertions(+), 3 deletions(-)

diff --git a/drivers/cpufreq/qcom-cpufreq-nvmem.c b/drivers/cpufreq/qcom-cpufreq-nvmem.c index 82a244f3fa52..3794390089b0 100644 --- a/drivers/cpufreq/qcom-cpufreq-nvmem.c +++ b/drivers/cpufreq/qcom-cpufreq-nvmem.c @@ -25,6 +25,7 @@ #include <linux/platform_device.h> #include <linux/pm_domain.h> #include <linux/pm_opp.h> +#include <linux/pm_runtime.h> #include <linux/slab.h> #include <linux/soc/qcom/smem.h>

@@ -47,6 +48,7 @@ struct qcom_cpufreq_match_data {

struct qcom_cpufreq_drv_cpu { int opp_token;

•   struct device **virt_devs;
  

};

struct qcom_cpufreq_drv { @@ -268,6 +270,18 @@ static const struct qcom_cpufreq_match_data match_data_ipq8074 = { .get_version = qcom_cpufreq_ipq8074_name_version, };

+static void qcom_cpufreq_put_virt_devs(struct qcom_cpufreq_drv *drv, unsigned cpu) +{

•   const char * const *name = drv->data->genpd_names;
  

•   int i;
  

•   if (!drv->cpus[cpu].virt_devs)
  

•           return;
  

•   for (i = 0; *name; i++, name++)
  

•           pm_runtime_put(drv->cpus[cpu].virt_devs[i]);
  

+}

static int qcom_cpufreq_probe(struct platform_device *pdev) { struct qcom_cpufreq_drv *drv; @@ -321,6 +335,7 @@ static int qcom_cpufreq_probe(struct platform_device *pdev) of_node_put(np);

    for_each_possible_cpu(cpu) {

•           struct device **virt_devs = NULL;
            struct dev_pm_opp_config config = {
                    .supported_hw = NULL,
            };
  

@@ -341,7 +356,7 @@ static int qcom_cpufreq_probe(struct platform_device *pdev)

            if (drv->data->genpd_names) {
                    config.genpd_names = drv->data->genpd_names;

•                   config.virt_devs = NULL;
  

•                   config.virt_devs = &virt_devs;
            }
  
            if (config.supported_hw || config.genpd_names) {
  

@@ -352,6 +367,30 @@ static int qcom_cpufreq_probe(struct platform_device *pdev) goto free_opp; } }

•           if (virt_devs) {
  

•                   const char * const *name = config.genpd_names;
  

•                   int i, j;
  

•                   for (i = 0; *name; i++, name++) {
  

•                           ret = pm_runtime_resume_and_get(virt_devs[i]);
  

•                           if (ret) {
  

•                                   dev_err(cpu_dev, "failed to resume %s: %d\n",
  

•                                           *name, ret);
  

•                                   /* Rollback previous PM runtime calls */
  

•                                   name = config.genpd_names;
  

•                                   for (j = 0; *name && j < i; j++, name++)
  

•                                           pm_runtime_put(virt_devs[j]);
  

•                                   goto free_opp;
  

•                           }
  

•                           /* Keep CPU power domain always-on */
  

•                           dev_pm_syscore_device(virt_devs[i], true);
  

•                   }
  

•                   drv->cpus[cpu].virt_devs = virt_devs;
  

•           }
    }
  
    cpufreq_dt_pdev = platform_device_register_simple("cpufreq-dt", -1,
  

@@ -365,8 +404,10 @@ static int qcom_cpufreq_probe(struct platform_device *pdev) dev_err(cpu_dev, "Failed to register platform device\n");

free_opp:

•   for_each_possible_cpu(cpu)
  

•   for_each_possible_cpu(cpu) {
  

•           qcom_cpufreq_put_virt_devs(drv, cpu);
            dev_pm_opp_clear_config(drv->cpus[cpu].opp_token);
  

•   }
    return ret;
  

}

@@ -377,8 +418,10 @@ static void qcom_cpufreq_remove(struct platform_device *pdev)

    platform_device_unregister(cpufreq_dt_pdev);

•   for_each_possible_cpu(cpu)
  

•   for_each_possible_cpu(cpu) {
  

•           qcom_cpufreq_put_virt_devs(drv, cpu);
            dev_pm_opp_clear_config(drv->cpus[cpu].opp_token);
  

•   }
  

}

static struct platform_driver qcom_cpufreq_driver = {

-- 2.39.2