linux-kernel - Re: [PATCH v2 06/10] drm/ingenic: Set DMA descriptor chain address in probe

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Message-ID: <20200630114453.GB560155@ravnborg.org>
Date:   Tue, 30 Jun 2020 13:44:53 +0200
From:   Sam Ravnborg <sam@...nborg.org>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     David Airlie <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        linux-mips@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, od@...c.me
Subject: Re: [PATCH v2 06/10] drm/ingenic: Set DMA descriptor chain address
 in probe

Hi Paul.

On Tue, Jun 30, 2020 at 01:52:06AM +0200, Paul Cercueil wrote:
> The address of the DMA descriptor never changes. It can therefore be set
> in the probe function.
> 
> Signed-off-by: Paul Cercueil <paul@...pouillou.net>
> ---
> 
> Notes:
>     v2: No change
> 
>  drivers/gpu/drm/ingenic/ingenic-drm-drv.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/ingenic/ingenic-drm-drv.c b/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> index 924c8daf071a..f7b0c5dc8cd8 100644
> --- a/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> +++ b/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> @@ -358,8 +358,6 @@ static void ingenic_drm_crtc_atomic_flush(struct drm_crtc *crtc,
>  		ingenic_drm_crtc_update_ctrl(priv, finfo);
>  
>  		clk_set_rate(priv->pix_clk, state->adjusted_mode.clock * 1000);
> -
> -		regmap_write(priv->map, JZ_REG_LCD_DA0, priv->dma_hwdesc->next);
>  	}
>  
>  	if (event) {
> @@ -757,6 +755,9 @@ static int ingenic_drm_probe(struct platform_device *pdev)
>  		}
>  	}
>  
> +	/* Set address of our DMA descriptor chain */
> +	regmap_write(priv->map, JZ_REG_LCD_DA0, priv->dma_hwdesc_phys);
> +

What is the purpose of this code after the assignment was moved:

static int ingenic_drm_probe(struct platform_device *pdev)
{
...
	priv->dma_hwdesc->next = priv->dma_hwdesc_phys;

I do not see ->next used anymore.
Could this assignment be dropped?

And the following line:
	priv->dma_hwdesc->id = 0xdeafbead;

I can only see ->id be assingned, it is never referenced??

Maybe this is all related to the structure assumed by the data pointed
to by JZ_REG_LCD_DA0?

	Sam

>  	ret = drm_dev_register(drm, 0);
>  	if (ret) {
>  		dev_err(dev, "Failed to register DRM driver\n");
> -- 
> 2.27.0
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@...ts.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

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