Hi, Guenter,
Thanks for your test and comment.
On Wed, 2017-06-21 at 14:14 -0700, Guenter Roeck wrote:
> On Fri, May 19, 2017 at 05:57:23PM +0800, Bibby Hsieh wrote:
> > For some greater resolution, the rdma threshold
> > variable will overflow.
> >
> > Signed-off-by: Bibby Hsieh <bibby.hsieh@xxxxxxxxxxxx>
> > ---
> > drivers/gpu/drm/mediatek/mtk_disp_rdma.c | 7 ++++---
> > 1 file changed, 4 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/mediatek/mtk_disp_rdma.c b/drivers/gpu/drm/mediatek/mtk_disp_rdma.c
> > index 0df05f9..9afdcd7 100644
> > --- a/drivers/gpu/drm/mediatek/mtk_disp_rdma.c
> > +++ b/drivers/gpu/drm/mediatek/mtk_disp_rdma.c
> > @@ -37,7 +37,7 @@
> > #define DISP_REG_RDMA_FIFO_CON 0x0040
> > #define RDMA_FIFO_UNDERFLOW_EN BIT(31)
> > #define RDMA_FIFO_PSEUDO_SIZE(bytes) (((bytes) / 16) << 16)
> > -#define RDMA_OUTPUT_VALID_FIFO_THRESHOLD(bytes) ((bytes) / 16)
> > +#define RDMA_OUTPUT_VALID_FIFO_THRESHOLD(bytes) (((bytes) / 16) & 0x3ff)
>
> I agree with the earlier comment; clamp_val() might be more appropriate here
> and would avoid unexpected results.
>
Yep, It's a good suggestion to me, I will add clamp_val() to avoid
unexpected value, thanks.
> >
> > /**
> > * struct mtk_disp_rdma - DISP_RDMA driver structure
> > @@ -109,7 +109,7 @@ static void mtk_rdma_config(struct mtk_ddp_comp *comp, unsigned int width,
> > unsigned int height, unsigned int vrefresh,
> > unsigned int bpc)
> > {
> > - unsigned int threshold;
> > + unsigned long long threshold;
> > unsigned int reg;
> >
> > rdma_update_bits(comp, DISP_REG_RDMA_SIZE_CON_0, 0xfff, width);
> > @@ -121,7 +121,8 @@ static void mtk_rdma_config(struct mtk_ddp_comp *comp, unsigned int width,
> > * output threshold to 6 microseconds with 7/6 overhead to
> > * account for blanking, and with a pixel depth of 4 bytes:
> > */
> > - threshold = width * height * vrefresh * 4 * 7 / 1000000;
> > + threshold = (unsigned long long)width * height * vrefresh *
> > + 4 * 7 / 1000000;
>
> This is a 64 bit divide operation. It will result in a build failure
> if compiled for a 32 bit kernel (eg arm:allmodconfig).
>
> ERROR: "__aeabi_uldivmod" [drivers/gpu/drm/mediatek/mediatek-drm.ko] undefined!
>
Sorry about the lack of tests, I will change the divide operation to
div_u64 function, thanks for your suggestions.
> Guenter
--
Bibby
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