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

From: Sam Ravnborg
Date: Tue Jun 30 2020 - 07:45:01 EST


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@xxxxxxxxxxxxxxx>
> ---
>
> 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
>
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