Re: [PATCH v8 11/21] clk: tegra: clk-dfll: Add suspend and resume support

[Thierry Reding]

On Thu, Aug 08, 2019 at 04:46:50PM -0700, Sowjanya Komatineni wrote:
> This patch implements DFLL suspend and resume operation.
> 
> During system suspend entry, CPU clock will switch CPU to safe
> clock source of PLLP and disables DFLL clock output.
> 
> DFLL driver suspend confirms DFLL disable state and errors out on
> being active.
> 
> DFLL is re-initialized during the DFLL driver resume as it goes
> through complete reset during suspend entry.
> 
> Signed-off-by: Sowjanya Komatineni <skomatin...@nvidia.com>
> ---
>  drivers/clk/tegra/clk-dfll.c               | 56 
> ++++++++++++++++++++++++++++++
>  drivers/clk/tegra/clk-dfll.h               |  2 ++
>  drivers/clk/tegra/clk-tegra124-dfll-fcpu.c |  1 +
>  3 files changed, 59 insertions(+)
> 
> diff --git a/drivers/clk/tegra/clk-dfll.c b/drivers/clk/tegra/clk-dfll.c
> index f8688c2ddf1a..eb298a5d7be9 100644
> --- a/drivers/clk/tegra/clk-dfll.c
> +++ b/drivers/clk/tegra/clk-dfll.c
> @@ -1487,6 +1487,7 @@ static int dfll_init(struct tegra_dfll *td)
>       td->last_unrounded_rate = 0;
>  
>       pm_runtime_enable(td->dev);
> +     pm_runtime_irq_safe(td->dev);
>       pm_runtime_get_sync(td->dev);
>  
>       dfll_set_mode(td, DFLL_DISABLED);
> @@ -1513,6 +1514,61 @@ static int dfll_init(struct tegra_dfll *td)
>       return ret;
>  }
>  
> +/**
> + * tegra_dfll_suspend - check DFLL is disabled
> + * @dev: DFLL device *
> + *
> + * DFLL clock should be disabled by the CPUFreq driver. So, make
> + * sure it is disabled and disable all clocks needed by the DFLL.
> + */
> +int tegra_dfll_suspend(struct device *dev)
> +{
> +     struct tegra_dfll *td = dev_get_drvdata(dev);
> +
> +     if (dfll_is_running(td)) {
> +             dev_err(td->dev, "dfll is enabled while shouldn't be\n");

Minor nit: "DFLL" in the error message, just like you have in the
kerneldoc comment above. Perhaps also make the error message a little
more specific. "while shouldn't be" makes the user guess what that
means. Perhaps better to say something like:

        "DFLL still enabled while suspending\n"

or perhaps even add a hint as to what could be the culprit:

        "DFLL still enabled while suspending, possibly a cpufreq driverbug\n"

The latter is somewhat long and the former is enough because the
kerneldoc comment already explains that cpufreq might be the reason for
this.

With a more specific error message, this is:

Acked-by: Thierry Reding <tred...@nvidia.com>

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