[PATCH 05/12] drm/ast: Fix calculation of MCLK

[Joel Stanley]

On Fri, Feb 24, 2017 at 9:23 AM, Benjamin Herrenschmidt
<benh at kernel.crashing.org> wrote:
> Some braces were missing causing an incorrect calculation.
>
> Y.C. Chen from Aspeed provided me with the right formula
> which I tested on AST2400 and 2500.

Y. C. Chen, can you point out this calculation in the programming guide?

All of the PLL calculations I can find in the ast2400 documentation
are different to this one.

Cheers,

Joel

>
> The MCLK isn't currently used by the driver (it will eventually
> to filter modes) so the issue isn't catastrophic.
>
> Also make the printed value a bit more meaningful
>
> Signed-off-by: Benjamin Herrenschmidt <benh at kernel.crashing.org>
> ---
>  drivers/gpu/drm/ast/ast_main.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/ast/ast_main.c b/drivers/gpu/drm/ast/ast_main.c
> index 718c15b..d194af3 100644
> --- a/drivers/gpu/drm/ast/ast_main.c
> +++ b/drivers/gpu/drm/ast/ast_main.c
> @@ -352,7 +352,7 @@ static int ast_get_dram_info(struct drm_device *dev)
>                 div = 0x1;
>                 break;
>         }
> -       ast->mclk = ref_pll * (num + 2) / (denum + 2) * (div * 1000);
> +       ast->mclk = ref_pll * (num + 2) / ((denum + 2) * (div * 1000));
>         return 0;
>  }
>
> @@ -496,7 +496,9 @@ int ast_driver_load(struct drm_device *dev, unsigned long flags)
>                 if (ret)
>                         goto out_free;
>                 ast->vram_size = ast_get_vram_info(dev);
> -               DRM_INFO("dram %d %d %d %08x\n", ast->mclk, ast->dram_type, ast->dram_bus_width, ast->vram_size);
> +               DRM_INFO("dram MCLK=%u Mhz type=%d bus_width=%d size=%08x\n",
> +                        ast->mclk, ast->dram_type,
> +                        ast->dram_bus_width, ast->vram_size);
>         }
>
>         if (need_post)
> --
> 2.9.3
>