On Sat, Apr 16, 2016 at 2:07 AM, Vineet Gupta
<Vineet.Gupta1@xxxxxxxxxxxx> wrote:
> On Friday 15 April 2016 09:18 PM, Alexey Brodkin wrote:
>
>> And now the question is how to force DRM subsystem or just that driver
>> to use whatever predefined (say via device tree) location in memory
>> for data buffer allocation.
>
> It seems this is pretty easy to do with DT reserved-memory binding.
>
> You need to partition memory into @memory and @reserved-memory.
> Later can be subdivided into more granular regions and your driver can refer to
> one of the regions.
jfyi, it might be useful to look at msm_init_vram() which has support
to wrap vram carveout as gem buffer, for exact same purpose..
BR,
-R
> Something like below (untested)
>
> + memory {
> + device_type = "memory";
> + reg = <0x0 0x80000000 0x0 0xA0000000>;
> + #address-cells = <2>;
> + #size-cells = <2>;
> + };
> +
> + reserved-memory {
> + #address-cells = <2>;
> + #size-cells = <2>;
> + ranges;
> + /* This memory bypasses IOC port */
> + fb_reserved@A0000000 {
> + reg = <0x0 0xA0000000 0x0 0xAF000000>;
> + #address-cells = <2>;
> + #size-cells = <2>;
> + /* no-map; */
> + };
> + };
> +
> +
> + fb0: video@12300000 {
> + memory-region = <&fb_reserved>;
> + /* ... */
> + };
>
> This might also need a DT helper in ARC mm init code.
>
> + early_init_fdt_scan_reserved_mem();
>
> HTH,
> -Vineet
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