[PATCH] drm: rcar-du: Fix external clock error checks

[Kieran Bingham]

Hi Laurent,

Thank you for the patch,

On 06/11/2018 15:39, Laurent Pinchart wrote:
> The rcar-du driver supports probe deferral for external clocks, but
> implements it badly by checking the wrong pointer due to a bad copy and
> paste. Fix it.
> 
> While at it, reject invalid clocks outright for DU channels that have a
> display PLL, as the external clock is mandatory in that case. This
> avoids a WARN_ON() at runtime.
> 
> Fixes: 1b30dbde8596 ("drm: rcar-du: Add support for external pixel clock")
> Reported-by: Kuninori Morimoto <kuninori.morimoto.gx at renesas.com>
> Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas at ideasonboard.com>

This looks good to me:

Reviewed-by: Kieran Bingham <kieran.bingham+renesas at ideasonboard.com>

> ---
>  drivers/gpu/drm/rcar-du/rcar_du_crtc.c | 14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/rcar-du/rcar_du_crtc.c b/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
> index d18a342626b5..79021d7aa3ce 100644
> --- a/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
> +++ b/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
> @@ -226,9 +226,6 @@ static void rcar_du_crtc_set_display_timing(struct rcar_du_crtc *rcrtc)
>  		 * system clock, and have no internal clock divider.
>  		 */
>  
> -		if (WARN_ON(!rcrtc->extclock))
> -			return;
> -
>  		/*
>  		 * The H3 ES1.x exhibits dot clock duty cycle stability issues.
>  		 * We can work around them by configuring the DPLL to twice the
> @@ -1113,9 +1110,16 @@ int rcar_du_crtc_create(struct rcar_du_group *rgrp, unsigned int swindex,
>  	clk = devm_clk_get(rcdu->dev, clk_name);
>  	if (!IS_ERR(clk)) {
>  		rcrtc->extclock = clk;
> -	} else if (PTR_ERR(rcrtc->clock) == -EPROBE_DEFER) {
> -		dev_info(rcdu->dev, "can't get external clock %u\n", hwindex);
> +	} else if (PTR_ERR(clk) == -EPROBE_DEFER) {
>  		return -EPROBE_DEFER;
> +	} else if (rcdu->info->dpll_mask & BIT(hwindex)) {
> +		/*
> +		 * DU channels that have a display PLL can't use the internal
> +		 * system clock and thus require an external clock.
> +		 */
> +		ret = PTR_ERR(clk);
> +		dev_err(rcdu->dev, "can't get dclkin.%u: %d\n", hwindex, ret);
> +		return ret;
>  	}
>  
>  	init_waitqueue_head(&rcrtc->flip_wait);
>