On Mon, Aug 31, 2020 at 10:39 AM Dmitry Osipenko <digetx@xxxxxxxxx> wrote:
>
> The enter() callback of CPUIDLE drivers returns index of the entered idle
> state on success or a negative value on failure. The negative value could
> any negative value, i.e. it doesn't necessarily needs to be a error code.
> That's because CPUIDLE core only cares about the fact of failure and not
> about the reason of the enter() failure.
>
> Like every other enter() callback, the arm_cpuidle_simple_enter() returns
> the entered idle-index on success. Unlike some of other drivers, it never
> fails. It happened that TEGRA_C1=index=err=0 in the code of cpuidle-tegra
> driver, and thus, there is no problem for the cpuidle-tegra driver created
> by the typo in the code which assumes that the arm_cpuidle_simple_enter()
> returns a error code.
>
> The arm_cpuidle_simple_enter() also may return a -ENODEV error if CPU_IDLE
> is disabled in a kernel's config, but all CPUIDLE drivers are disabled if
> CPU_IDLE is disabled, including the cpuidle-tegra driver. So we can't ever
> see the error code from arm_cpuidle_simple_enter() today.
>
> Of course the code may get some changes in the future and then the
> typo may transform into a real bug, so let's correct the typo! The
> tegra_cpuidle_state_enter() is now changed to make it return the entered
> idle-index on success and negative error code on fail, which puts it on
> par with the arm_cpuidle_simple_enter(), making code consistent in regards
> to the error handling.
>
> This patch fixes a minor typo in the code, it doesn't fix any bugs.
>
> Reviewed-by: Jon Hunter <jonathanh@xxxxxxxxxx>
> Signed-off-by: Dmitry Osipenko <digetx@xxxxxxxxx>
Applied as 5.10 material, thanks!
> ---
>
> Changelog:
>
> v4: No code changes. Added r-b from Jon Hunter and re-sending for 5.10.
>
> v3: The tegra_cpuidle_state_enter() now returns entered idle-index on
> success instead of 0. Hence the error message will be shown by the
> tegra-cpuidle driver if arm_cpuidle_simple_enter() will ever fail.
> Again thanks to Jon Hunter!
>
> v2: Improved commit message by clarifying what values are returned by
> arm_cpuidle_simple_enter() and when. Thanks to Jon Hunter for the
> suggestion!
>
> drivers/cpuidle/cpuidle-tegra.c | 34 +++++++++++++++++++--------------
> 1 file changed, 20 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/cpuidle/cpuidle-tegra.c b/drivers/cpuidle/cpuidle-tegra.c
> index a12fb141875a..e8956706a291 100644
> --- a/drivers/cpuidle/cpuidle-tegra.c
> +++ b/drivers/cpuidle/cpuidle-tegra.c
> @@ -172,7 +172,7 @@ static int tegra_cpuidle_coupled_barrier(struct cpuidle_device *dev)
> static int tegra_cpuidle_state_enter(struct cpuidle_device *dev,
> int index, unsigned int cpu)
> {
> - int ret;
> + int err;
>
> /*
> * CC6 state is the "CPU cluster power-off" state. In order to
> @@ -183,9 +183,9 @@ static int tegra_cpuidle_state_enter(struct cpuidle_device *dev,
> * CPU cores, GIC and L2 cache).
> */
> if (index == TEGRA_CC6) {
> - ret = tegra_cpuidle_coupled_barrier(dev);
> - if (ret)
> - return ret;
> + err = tegra_cpuidle_coupled_barrier(dev);
> + if (err)
> + return err;
> }
>
> local_fiq_disable();
> @@ -194,15 +194,15 @@ static int tegra_cpuidle_state_enter(struct cpuidle_device *dev,
>
> switch (index) {
> case TEGRA_C7:
> - ret = tegra_cpuidle_c7_enter();
> + err = tegra_cpuidle_c7_enter();
> break;
>
> case TEGRA_CC6:
> - ret = tegra_cpuidle_cc6_enter(cpu);
> + err = tegra_cpuidle_cc6_enter(cpu);
> break;
>
> default:
> - ret = -EINVAL;
> + err = -EINVAL;
> break;
> }
>
> @@ -210,7 +210,7 @@ static int tegra_cpuidle_state_enter(struct cpuidle_device *dev,
> tegra_pm_clear_cpu_in_lp2();
> local_fiq_enable();
>
> - return ret;
> + return err ?: index;
> }
>
> static int tegra_cpuidle_adjust_state_index(int index, unsigned int cpu)
> @@ -236,21 +236,27 @@ static int tegra_cpuidle_enter(struct cpuidle_device *dev,
> int index)
> {
> unsigned int cpu = cpu_logical_map(dev->cpu);
> - int err;
> + int ret;
>
> index = tegra_cpuidle_adjust_state_index(index, cpu);
> if (dev->states_usage[index].disable)
> return -1;
>
> if (index == TEGRA_C1)
> - err = arm_cpuidle_simple_enter(dev, drv, index);
> + ret = arm_cpuidle_simple_enter(dev, drv, index);
> else
> - err = tegra_cpuidle_state_enter(dev, index, cpu);
> + ret = tegra_cpuidle_state_enter(dev, index, cpu);
>
> - if (err && (err != -EINTR || index != TEGRA_CC6))
> - pr_err_once("failed to enter state %d err: %d\n", index, err);
> + if (ret < 0) {
> + if (ret != -EINTR || index != TEGRA_CC6)
> + pr_err_once("failed to enter state %d err: %d\n",
> + index, ret);
> + index = -1;
> + } else {
> + index = ret;
> + }
>
> - return err ? -1 : index;
> + return index;
> }
>
> static int tegra114_enter_s2idle(struct cpuidle_device *dev,
> --
> 2.27.0
>
