[PATCH 5/7] drm/sun4i: Rely on dma-parent for our RAM offset

[daniel@ffwll.ch (Daniel Vetter)]

On Tue, Apr 03, 2018 at 03:29:18PM +0200, Maxime Ripard wrote:
> Now that we can express our DMA topology, rely on those property instead of
> hardcoding an offset from the dma_addr_t which wasn't really great.
> 
> We still need to add some code to deal with the old DT that would lack that
> property, but we move the offset to the DRM device dma_pfn_offset to be
> able to rely on just the dma_addr_t associated to the GEM object.
> 
> Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>

Yay for hiding more bus address funies behind dma_map_* support. This
should also help with cleaner dma-buf import.

Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> ---
>  drivers/gpu/drm/sun4i/sun4i_backend.c | 28 +++++++++++++++++++++-------
>  1 file changed, 21 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/sun4i/sun4i_backend.c b/drivers/gpu/drm/sun4i/sun4i_backend.c
> index 847eecbe4d14..04e85d3ca36e 100644
> --- a/drivers/gpu/drm/sun4i/sun4i_backend.c
> +++ b/drivers/gpu/drm/sun4i/sun4i_backend.c
> @@ -222,13 +222,6 @@ int sun4i_backend_update_layer_buffer(struct sun4i_backend *backend,
>  	paddr = drm_fb_cma_get_gem_addr(fb, state, 0);
>  	DRM_DEBUG_DRIVER("Setting buffer address to %pad\n", &paddr);
>  
> -	/*
> -	 * backend DMA accesses DRAM directly, bypassing the system
> -	 * bus. As such, the address range is different and the buffer
> -	 * address needs to be corrected.
> -	 */
> -	paddr -= PHYS_OFFSET;
> -
>  	/* Write the 32 lower bits of the address (in bits) */
>  	lo_paddr = paddr << 3;
>  	DRM_DEBUG_DRIVER("Setting address lower bits to 0x%x\n", lo_paddr);
> @@ -361,6 +354,27 @@ static int sun4i_backend_bind(struct device *dev, struct device *master,
>  		return -ENOMEM;
>  	dev_set_drvdata(dev, backend);
>  
> +	if (of_find_property(dev->of_node, "dma-parent", NULL)) {
> +		/*
> +		 * This assume we have the same DMA constraints for all our the
> +		 * devices in our pipeline (all the backends, but also the
> +		 * frontends). This sounds bad, but it has always been the case
> +		 * for us, and DRM doesn't do per-device allocation either, so
> +		 * we would need to fix DRM first...
> +		 */
> +		ret = of_dma_configure(drm->dev, dev->of_node);
> +		if (ret)
> +			return ret;
> +	} else {
> +		/*
> +		 * If we don't have the dma-parent property, most likely
> +		 * because of an old DT, we need to set the DMA offset by hand
> +		 * on our device since the RAM mapping is at 0 for the DMA bus,
> +		 * unlike the CPU.
> +		 */
> +		drm->dev->dma_pfn_offset = PHYS_PFN_OFFSET;
> +	}
> +
>  	backend->engine.node = dev->of_node;
>  	backend->engine.ops = &sun4i_backend_engine_ops;
>  	backend->engine.id = sun4i_backend_of_get_id(dev->of_node);
> -- 
> git-series 0.9.1
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch