[PATCH 5/9] drm/bridge: synopsys: dw-mipi-dsi: Use pixel clock rate to calculate lbcc

[neil.armstrong at linaro.org]

On 17/07/2023 08:18, Liu Ying wrote:
> To get better accuration, use pixel clock rate to calculate lbcc instead of
> lane_mbps since the pixel clock rate is in KHz while lane_mbps is in MHz.
> Without this, distorted image can be seen on a HDMI monitor connected with
> i.MX93 11x11 EVK through ADV7535 DSI to HDMI bridge in 1920x1080p at 60 video
> mode.
> 
> Signed-off-by: Liu Ying <victor.liu at nxp.com>
> ---
>   drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c | 10 +++++++++-
>   1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> index c754d55f71d1..332388fd86da 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> @@ -12,6 +12,7 @@
>   #include <linux/component.h>
>   #include <linux/debugfs.h>
>   #include <linux/iopoll.h>
> +#include <linux/math64.h>
>   #include <linux/media-bus-format.h>
>   #include <linux/module.h>
>   #include <linux/of_device.h>
> @@ -762,8 +763,15 @@ static u32 dw_mipi_dsi_get_hcomponent_lbcc(struct dw_mipi_dsi *dsi,
>   					   u32 hcomponent)
>   {
>   	u32 frac, lbcc;
> +	int bpp;
>   
> -	lbcc = hcomponent * dsi->lane_mbps * MSEC_PER_SEC / 8;
> +	bpp = mipi_dsi_pixel_format_to_bpp(dsi->format);
> +	if (bpp < 0) {
> +		dev_err(dsi->dev, "failed to get bpp\n");
> +		return 0;
> +	}
> +
> +	lbcc = div_u64((u64)hcomponent * mode->clock * bpp, dsi->lanes * 8);
>   
>   	frac = lbcc % mode->clock;
>   	lbcc = lbcc / mode->clock;

Reviewed-by: Neil Armstrong <neil.armstrong at linaro.org>