[PATCH] drm/pl111: Enable device-specific assigned memory

[Eric Anholt]

Linus Walleij <linus.walleij at linaro.org> writes:

> The Versatile Express has 8 MB of dedicated video RAM (VRAM)
> on the motherboard, which is what we should be using for the
> PL111 if available. On this platform, the memory backplane
> is constructed so that only this memory will work properly
> with the CLCD on the motherboard, using any other memory
> region just gives random snow on the display.
>
> The CA9 Versatile Express also has a PL111 instance on its
> core tile. This is OK, it has been tested with the motherboard
> VRAM and that works just as fine as regular CMA memory.
>
> The memory is assigned to the device using the memory-region
> device tree property and a "shared-dma-pool" reserved
> memory pool like this:
>
> reserved-memory {
>         #address-cells = <1>;
>         #size-cells = <1>;
>         ranges;
>
>         vram: vram at 48000000 {
>                 compatible = "shared-dma-pool";
>                 reg = <0x48000000 0x00800000>;
>                 no-map;
>         };
> };
>
> clcd at 1f000 {
>         compatible = "arm,pl111", "arm,primecell";
> 	(...)
>         memory-region = <&vram>;
> }·;
>
> Cc: Liviu Dudau <liviu.dudau at arm.com>
> Cc: Mali DP Maintainers <malidp at foss.arm.com>
> Signed-off-by: Linus Walleij <linus.walleij at linaro.org>
> ---
>  drivers/gpu/drm/pl111/pl111_drv.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/drivers/gpu/drm/pl111/pl111_drv.c b/drivers/gpu/drm/pl111/pl111_drv.c
> index b469aa317d9d..e301f2a719a3 100644
> --- a/drivers/gpu/drm/pl111/pl111_drv.c
> +++ b/drivers/gpu/drm/pl111/pl111_drv.c
> @@ -60,6 +60,7 @@
>  #include <linux/slab.h>
>  #include <linux/of.h>
>  #include <linux/of_graph.h>
> +#include <linux/of_reserved_mem.h>
>  
>  #include <drm/drmP.h>
>  #include <drm/drm_atomic_helper.h>
> @@ -262,6 +263,10 @@ static int pl111_amba_probe(struct amba_device *amba_dev,
>  	drm->dev_private = priv;
>  	priv->variant = variant;
>  
> +	ret = of_reserved_mem_device_init(dev);
> +	if (!ret)
> +		dev_info(dev, "using device-specific reserved memory\n");
> +
>  	if (of_property_read_u32(dev->of_node, "max-memory-bandwidth",
>  				 &priv->memory_bw)) {
>  		dev_info(dev, "no max memory bandwidth specified, assume unlimited\n");
> -- 
> 2.14.3

It looks like you'll want a matching of_reserved_mem_device_release() at
remove / dev_unref time.

This will still allow BO imports from non-reserved memory, I think.
Should we just error out of import_sg_table() on this platform?
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