Re: [PATCH v1 3/9] drm/bridge: tc358768: fix PLL target frequency

[Robert Foss]

On Thu, Apr 27, 2023 at 4:32 PM Francesco Dolcini <francesco@xxxxxxxxxx> wrote:
>
> From: Francesco Dolcini <francesco.dolcini@xxxxxxxxxxx>
>
> Correctly compute the PLL target frequency, the current formula works
> correctly only when the input bus width is 24bit, actually to properly
> compute the PLL target frequency what is relevant is the bits-per-pixel
> on the DSI link.
>
> No regression expected since the DSI format is currently hard-coded as
> MIPI_DSI_FMT_RGB888.
>
> Fixes: ff1ca6397b1d ("drm/bridge: Add tc358768 driver")
> Signed-off-by: Francesco Dolcini <francesco.dolcini@xxxxxxxxxxx>
> ---
>  drivers/gpu/drm/bridge/tc358768.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/tc358768.c b/drivers/gpu/drm/bridge/tc358768.c
> index e9e3f9e02bba..dba1bf3912f1 100644
> --- a/drivers/gpu/drm/bridge/tc358768.c
> +++ b/drivers/gpu/drm/bridge/tc358768.c
> @@ -146,6 +146,7 @@ struct tc358768_priv {
>
>         u32 pd_lines; /* number of Parallel Port Input Data Lines */
>         u32 dsi_lanes; /* number of DSI Lanes */
> +       u32 dsi_bpp; /* number of Bits Per Pixel over DSI */
>
>         /* Parameters for PLL programming */
>         u32 fbd;        /* PLL feedback divider */
> @@ -284,12 +285,12 @@ static void tc358768_hw_disable(struct tc358768_priv *priv)
>
>  static u32 tc358768_pll_to_pclk(struct tc358768_priv *priv, u32 pll_clk)
>  {
> -       return (u32)div_u64((u64)pll_clk * priv->dsi_lanes, priv->pd_lines);
> +       return (u32)div_u64((u64)pll_clk * priv->dsi_lanes, priv->dsi_bpp);
>  }
>
>  static u32 tc358768_pclk_to_pll(struct tc358768_priv *priv, u32 pclk)
>  {
> -       return (u32)div_u64((u64)pclk * priv->pd_lines, priv->dsi_lanes);
> +       return (u32)div_u64((u64)pclk * priv->dsi_bpp, priv->dsi_lanes);
>  }
>
>  static int tc358768_calc_pll(struct tc358768_priv *priv,
> @@ -426,6 +427,7 @@ static int tc358768_dsi_host_attach(struct mipi_dsi_host *host,
>         priv->output.panel = panel;
>
>         priv->dsi_lanes = dev->lanes;
> +       priv->dsi_bpp = mipi_dsi_pixel_format_to_bpp(dev->format);
>
>         /* get input ep (port0/endpoint0) */
>         ret = -EINVAL;
> @@ -437,7 +439,7 @@ static int tc358768_dsi_host_attach(struct mipi_dsi_host *host,
>         }
>
>         if (ret)
> -               priv->pd_lines = mipi_dsi_pixel_format_to_bpp(dev->format);
> +               priv->pd_lines = priv->dsi_bpp;
>
>         drm_bridge_add(&priv->bridge);
>
> --
> 2.25.1
>

Reviewed-by: Robert Foss <rfoss@xxxxxxxxxx>