linux-kernel - Re: [PATCH v1] clk: tegra: Adjust callbacks in tegra_clock

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Message-ID: <2d55ebec-1e42-4ddb-b0e2-529d3b2d7b85@nvidia.com>
Date: Tue, 6 Jan 2026 10:36:00 +0000
From: Jon Hunter <jonathanh@...dia.com>
To: "Rafael J. Wysocki" <rafael@...nel.org>, linux-tegra@...r.kernel.org,
 Linux PM <linux-pm@...r.kernel.org>
Cc: Peter De Schrijver <pdeschrijver@...dia.com>,
 Prashant Gaikwad <pgaikwad@...dia.com>,
 Michael Turquette <mturquette@...libre.com>, Stephen Boyd
 <sboyd@...nel.org>, Thierry Reding <thierry.reding@...il.com>,
 linux-clk@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
 Dmitry Osipenko <digetx@...il.com>, Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH v1] clk: tegra: Adjust callbacks in tegra_clock_pm

Hi Rafael,

On 04/01/2026 11:53, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> System suspend and resume callbacks run after the core has bumped
> up the runtime PM usage counters of all devices, so these callbacks
> need not worry about runtime PM reference counting.
> 
> Accordingly, to eliminate useless overhead related to runtime PM
> usage counter manipulation, set the suspend callback pointer in
> tegra_clock_pm to pm_runtime_resume() and do not set the resume
> callback in it at all.
> 
> This will also facilitate a planned change of the pm_runtime_put()
> return type to void in the future.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
> 
> This patch is requisite for converting pm_runtime_put() into a void
> function.
> 
> If you decide to pick it up, please let me know.
> 
> Otherwise, an ACK or equivalent will be appreciated, but also the lack
> of specific criticism will be eventually regarded as consent.
> 
> ---
>   drivers/clk/tegra/clk-device.c |    2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> --- a/drivers/clk/tegra/clk-device.c
> +++ b/drivers/clk/tegra/clk-device.c
> @@ -175,7 +175,7 @@ unreg_clk:
>    * perspective since voltage is kept at a nominal level during suspend anyways.
>    */
>   static const struct dev_pm_ops tegra_clock_pm = {
> -	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_resume_and_get, pm_runtime_put)
> +	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_resume, NULL)
>   };
>   
>   static const struct of_device_id tegra_clock_match[] = {

I gave this a quick test and this is causing a suspend regression on
Tegra20 and Tegra30 that use this driver. Looking at the console log
on Tegra20 I see the following errors ...

  tegra-clock tegra_clk_sclk: PM: dpm_run_callback(): pm_runtime_resume returns 1
  tegra-clock tegra_clk_sclk: PM: failed to suspend: error 1
  PM: Some devices failed to suspend, or early wake event detected

Jon

-- 
nvpublic