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On 13/10/17 12:35, Jyri Sarha wrote:
> We need the total frame refresh time to check if we are too close to
> vertical sync when updating the two framebuffer DMA registers and risk
> a collision. This new method is more accurate that the previous that
> based on mode's vrefresh value, which itself is inaccurate or may not
> even be initialized.
>
> Reported-by: Kevin Hao <kexin.hao@xxxxxxxxxxxxx>
> Fixes: 11abbc9f39e0 ("drm/tilcdc: Set framebuffer DMA address to HW only if CRTC is enabled")
> Cc: <stable@xxxxxxxxxxxxxxx> # v4.11+
> Signed-off-by: Jyri Sarha <jsarha@xxxxxx>
> ---
> Since first version:
>
> Change frametime* variable names to hvtotal and use 64-bit division
> instead of dynamcally scaled 32-bit division as suggested by Tomi
> Valkeinen.
>
> drivers/gpu/drm/tilcdc/tilcdc_crtc.c | 17 ++++++++++++++++-
> 1 file changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
> index 704db24..a8b22aa 100644
> --- a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
> +++ b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
> @@ -24,6 +24,7 @@
> #include <linux/completion.h>
> #include <linux/dma-mapping.h>
> #include <linux/of_graph.h>
> +#include <linux/math64.h>
>
> #include "tilcdc_drv.h"
> #include "tilcdc_regs.h"
> @@ -48,6 +49,7 @@ struct tilcdc_crtc {
> unsigned int lcd_fck_rate;
>
> ktime_t last_vblank;
> + unsigned int hvtotal_us;
>
> struct drm_framebuffer *curr_fb;
> struct drm_framebuffer *next_fb;
> @@ -292,6 +294,16 @@ static void tilcdc_crtc_set_clk(struct drm_crtc *crtc)
> LCDC_V2_CORE_CLK_EN);
> }
>
> +uint tilcdc_mode_hvtotal(const struct drm_display_mode *mode)
> +{
> + uint ret;
> +
> + ret = (uint) div_u64(1000llu * mode->htotal * mode->vtotal,
> + mode->clock);
> +
> + return ret;
> +}
I don't think "uint" is recommended. Just use u32. And drop the ret
variable, just one-line return statement should be enough.
Otherwise:
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@xxxxxx>
Tomi