linux-kernel - Re: [PATCH] drm/amd/powerplay: Change id parameter type in pp_atomfwctrl_get_clk_information_by

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Message-ID: <CAKwvOdkVqQN5M05X4_1YxOSi4LAzw=PXuLqVq0z7SXYWoCG2sA@mail.gmail.com>
Date:   Mon, 24 Sep 2018 15:02:01 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     natechancellor@...il.com
Cc:     rex.zhu@....com, evan.quan@....com, alexander.deucher@....com,
        christian.koenig@....com, David1.Zhou@....com,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/amd/powerplay: Change id parameter type in pp_atomfwctrl_get_clk_information_by_clkid

On Fri, Sep 21, 2018 at 2:01 PM Nathan Chancellor
<natechancellor@...il.com> wrote:
>
> Clang generates warnings when one enumerated type is implicitly
> converted to another.
>
> drivers/gpu/drm/amd/amdgpu/../powerplay/hwmgr/ppatomfwctrl.c:532:57:
> warning: implicit conversion from enumeration type 'enum
> atom_smu11_syspll0_clock_id' to different enumeration type 'BIOS_CLKID'
>       (aka 'enum atom_smu9_syspll0_clock_id') [-Wenum-conversion]
>         if (!pp_atomfwctrl_get_clk_information_by_clkid(hwmgr,
> SMU11_SYSPLL0_SOCCLK_ID, &frequency))

Grepping the call sites, via:
$ grep -r pp_atomfwctrl_get_clk_information_by_clkid

shows that sometimes this function is called with instances of:

enum atom_smu9_syspll0_clock_id
enum atom_smu11_syspll0_clock_id

before your patch, the function defined to take a BIOS_CLKID, which is
typedef'd to the *9* enum:

typedef enum atom_smu9_syspll0_clock_id BIOS_CLKID;

While the current values are < 256, the enums are not packed, so you
should use either int or a union of the two types.
Do the maintainers have a preference, before sending a v2?

>
> In this case, that is expected behavior. To make that clear to Clang
> without explicitly casting these values, change id's type to uint8_t
> in pp_atomfwctrl_get_clk_information_by_clkid so no conversion happens.
>
> Reported-by: Nick Desaulniers <ndesaulniers@...gle.com>
> Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> ---
>  drivers/gpu/drm/amd/powerplay/hwmgr/ppatomfwctrl.c | 3 ++-
>  drivers/gpu/drm/amd/powerplay/hwmgr/ppatomfwctrl.h | 2 +-
>  2 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/powerplay/hwmgr/ppatomfwctrl.c b/drivers/gpu/drm/amd/powerplay/hwmgr/ppatomfwctrl.c
> index d27c1c9df286..4588bddf8b33 100644
> --- a/drivers/gpu/drm/amd/powerplay/hwmgr/ppatomfwctrl.c
> +++ b/drivers/gpu/drm/amd/powerplay/hwmgr/ppatomfwctrl.c
> @@ -488,7 +488,8 @@ int pp_atomfwctrl_get_gpio_information(struct pp_hwmgr *hwmgr,
>         return 0;
>  }
>
> -int pp_atomfwctrl_get_clk_information_by_clkid(struct pp_hwmgr *hwmgr, BIOS_CLKID id, uint32_t *frequency)
> +int pp_atomfwctrl_get_clk_information_by_clkid(struct pp_hwmgr *hwmgr,
> +                                              uint8_t id, uint32_t *frequency)
>  {
>         struct amdgpu_device *adev = hwmgr->adev;
>         struct atom_get_smu_clock_info_parameters_v3_1   parameters;
> diff --git a/drivers/gpu/drm/amd/powerplay/hwmgr/ppatomfwctrl.h b/drivers/gpu/drm/amd/powerplay/hwmgr/ppatomfwctrl.h
> index 22e21668c93a..fe9e8ceef50e 100644
> --- a/drivers/gpu/drm/amd/powerplay/hwmgr/ppatomfwctrl.h
> +++ b/drivers/gpu/drm/amd/powerplay/hwmgr/ppatomfwctrl.h
> @@ -236,7 +236,7 @@ int pp_atomfwctrl_get_vbios_bootup_values(struct pp_hwmgr *hwmgr,
>  int pp_atomfwctrl_get_smc_dpm_information(struct pp_hwmgr *hwmgr,
>                         struct pp_atomfwctrl_smc_dpm_parameters *param);
>  int pp_atomfwctrl_get_clk_information_by_clkid(struct pp_hwmgr *hwmgr,
> -                                       BIOS_CLKID id, uint32_t *frequency);
> +                                       uint8_t id, uint32_t *frequency);
>
>  #endif
>
> --
> 2.19.0
>


--
Thanks,
~Nick Desaulniers