On 3/4/24 17:40, Mike Tipton wrote:
On Sat, Mar 02, 2024 at 03:22:49AM +0100, Konrad Dybcio wrote:Booting the kernel on X1E results in a message like: [ 2.561524] qnoc-x1e80100 interconnect-0: ACV_PERF could not find RPMh address And indeed, taking a look at cmd-db, no such BCM exists. Remove it. Fixes: 9f196772841e ("interconnect: qcom: Add X1E80100 interconnect provider driver") Signed-off-by: Konrad Dybcio <konrad.dybcio@xxxxxxxxxx>Reviewed-by: Mike Tipton <quic_mdtipton@xxxxxxxxxxx> For some background, ACV "perf mode" does exist, but not as a separate BCM. It's controlled by a separate bit in the ACV mask. By default, the ACV node only sets the bit indicating the HLOS voter. It doesn't assert the perf mode bit. Enabling perf mode toggles different trade-offs within the DDR subsystem for slightly improved performance at the expense of slightly higher power. There are limited use cases of this downstream, where we expose control over this bit to clients through icc_set_tag(). It primarily improves certain latency sensitive benchmarks, AFAIK. I don't think it has much impact on real world use cases. This is true for many other targets as well, not just x1e80100. Voting for perf-mode is entirely optional and in most cases also entirely unnecessary. So, removing this broken way to control it without adding the proper control is totally fine. I have a local series to add the proper support, but haven't posted it yet. There aren't any users for it upstream yet, nor am I aware of any near term plans to add them. So, it would be unused for a little while, at least. That said, anybody could use it to set that tag on their BW votes on the off-chance it improves performance and they don't care about the power trade-offs. I could post the series soon if there's interest.
I think adding a sysfs entry for toggling this could be very interesting. Userspace could toggle this based on "power profile"-style settings. Konrad
