On 15.07.2024 10:07 PM, Rob Clark wrote: > On Mon, Jul 15, 2024 at 4:00 AM Bibek Kumar Patro > <quic_bibekkum@xxxxxxxxxxx> wrote: [...] >>>> As I checked gpu_prr_mem reserved mem section is not used for mobile >>>> targets hence not present for other DT only compute targets like >>>> x1e80100.dtsi has the same. PRR looks to be smmu version specific >>>> property. >>> >>> I only see it in gpu_prr_mem in x1e80100.dtsi, but not documented >>> anywhere. I'm only assuming based on the name that it is intended to >>> be for PRR (but not sure why it is larger than 0x1000). Are the >>> PRR_CFG_*ADDR regs programmed by the fw (and access blocked in EL1) on >>> this device? >>> >> >> As I checked, if the drm/gfx driver allocates the page for drm, then >> this reserved-memory region is not required. >> >> PRR_CFG_*ADDR regs have read and write access in EL1 only for this >> device, behavior is same as other devices as well. These are not >> programmed by fw. > > If there is any device which _doesn't_ have EL1 access to these regs, > I think going the reserved memory route seems more future proof? > Otherwise we later on have to deal with two different ways to do > things. But I'm not sure if there is any such device or risk. We can have our cake and eat it too, if we keep the check for a reserved memory node handle, but make it a dynamic allocation (see [1] for example), this way there's a way to opt into using this from the DT and there's no need for adding more properties Konrad [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/boot/dts/qcom/msm8916.dtsi?h=v6.10#n109
