Re: [PATCH 06/10] drm/tegra: Handle 64-bit return from drm_crtc_vblank_count()

Pandiyan, Dhinakaran
2018-02-07T01:41:18Z

On Fri, 2018-02-02 at 21:12 -0800, Dhinakaran Pandiyan wrote:
> 570e86963a51 ("drm: Widen vblank count to 64-bits [v3]") changed the
> return type for drm_crtc_vblank_count() to u64. This could cause
> potential problems if the return value is used in arithmetic operations
> with a 32-bit reference HW vblank count. Explicitly typecasting this
> down to u32 either fixes a potential problem or serves to add clarity in
> case the implicit typecasting was already correct.
>
> Cc: Keith Packard <keithp@keithp.com>
> Cc: Thierry Reding <treding@nvidia.com>

Thierry,

Can I get an Ack on this please?

> Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
> ---
> drivers/gpu/drm/tegra/dc.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/tegra/dc.c b/drivers/gpu/drm/tegra/dc.c
> index b8403ed48285..49df2db2ad46 100644
> --- a/drivers/gpu/drm/tegra/dc.c
> +++ b/drivers/gpu/drm/tegra/dc.c
> @@ -1359,7 +1359,7 @@ static u32 tegra_dc_get_vblank_counter(struct drm_crtc *crtc)
> return host1x_syncpt_read(dc->syncpt);
>
> /* fallback to software emulated VBLANK counter */
> - return drm_crtc_vblank_count(&dc->base);
> + return (u32)drm_crtc_vblank_count(&dc->base);
> }
>
> static int tegra_dc_enable_vblank(struct drm_crtc *crtc)