Re: [PATCH v3 2/2] interconnect: qcom: add MSM8x60 NoC driver

[me@herrie.org]

On 2026-06-17 12:36, Konrad Dybcio wrote:
> On 6/6/26 2:34 PM, Herman van Hazendonk wrote:
>> Add a Qualcomm interconnect driver for the MSM8x60 family modelling 
>> the
>> four NoC fabrics (APPSS, System, MMSS, Daytona) that connect masters
>> and slaves on these Scorpion-class SoCs.  The driver implements the
>> interconnect-provider API to manage bandwidth between specific masters
>> and slaves via the RPM arbitration tables.
> 
> [...]
> 
> 
>> +/*
>> + * Minimum fabric clock rate to prevent bus starvation.
>> + *
>> + * When no consumers request bandwidth, the rate calculation yields 
>> 0,
>> + * causing fabric clocks to drop to minimum. This creates bimodal
>> + * performance: fast when other subsystems (like display) happen to
>> + * request bandwidth, slow otherwise.
>> + *
>> + * 384 MHz keeps fabric fast during concurrent MDP display scanout
>> + * and USB gadget traffic. legacy vendor kernel docs: "AXI bus 
>> frequency needs to be
>> + * kept at maximum value while USB data transfers are happening."
>> + * 266 MHz was insufficient - USB crashed during display activity.
>> + */
>> +#define MSM8660_FABRIC_MIN_RATE		384000000UL	/* 384 MHz */
> 
> Can you ensure that through a vote in the USB driver?
> 
> Konrad
Hi Konrad,

I'm reworking the interconnect driver based on earlier feedback, but 
running
into some regressions I need to tackle first. The driver I had was 
stable,
the reworked one has some issues that I'm trying to tackle before 
submitting
another version. The minimum rate will probably disappear as a result of 
that
anyway.

Thanks,
Herman