Linus Walleij <linus.walleij@xxxxxxxxxx> 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@48000000 {
> compatible = "shared-dma-pool";
> reg = <0x48000000 0x00800000>;
> no-map;
> };
> };
>
> clcd@1f000 {
> compatible = "arm,pl111", "arm,primecell";
> (...)
> memory-region = <&vram>;
> }·;
>
> Cc: Liviu Dudau <liviu.dudau@xxxxxxx>
> Cc: Mali DP Maintainers <malidp@xxxxxxxxxxxx>
> Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
> ---
> 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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