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

neil.armstrong
2023-08-01T09:54:33Z

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@60 video
> mode.
>
> Signed-off-by: Liu Ying <victor.liu@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@linaro.org>