Quoting Loic Poulain (2020-07-03 01:49:42) > Each of the CPU clusters (Power and Perf) on msm8996 are > clocked via 2 PLLs, a primary and alternate. There are also > 2 Mux'es, a primary and secondary all connected together > as shown below > > +-------+ > XO | | > +------------------>0 | > | | > PLL/2 | SMUX +----+ > +------->1 | | > | | | | > | +-------+ | +-------+ > | +---->0 | > | | | > +---------------+ | +----------->1 | CPU clk > |Primary PLL +----+ PLL_EARLY | | +------> > | +------+-----------+ +------>2 PMUX | > +---------------+ | | | | > | +------+ | +-->3 | > +--^+ ACD +-----+ | +-------+ > +---------------+ +------+ | > |Alt PLL | | > | +---------------------------+ > +---------------+ PLL_EARLY > > The primary PLL is what drives the CPU clk, except for times > when we are reprogramming the PLL itself (for rate changes) when > we temporarily switch to an alternate PLL. A subsequent patch adds > support to switch between primary and alternate PLL during rate > changes. > > The primary PLL operates on a single VCO range, between 600MHz > and 3GHz. However the CPUs do support OPPs with frequencies > between 300MHz and 600MHz. In order to support running the CPUs > at those frequencies we end up having to lock the PLL at twice > the rate and drive the CPU clk via the PLL/2 output and SMUX. > > So for frequencies above 600MHz we follow the following path > Primary PLL --> PLL_EARLY --> PMUX(1) --> CPU clk > and for frequencies between 300MHz and 600MHz we follow > Primary PLL --> PLL/2 --> SMUX(1) --> PMUX(0) --> CPU clk > > ACD stands for Adaptive Clock Distribution and is used to > detect voltage droops. > > Signed-off-by: Rajendra Nayak <rnayak@xxxxxxxxxxxxxx> > Rajendra Nayak: Initial RFC - https://lkml.org/lkml/2016/9/29/84 > > Signed-off-by: Ilia Lin <ilialin@xxxxxxxxxxxxxx> > Ilia Lin: - reworked clock registering > - Added clock-tree diagram > - non-builtin support > - clock notifier on rate change > - https://lkml.org/lkml/2018/5/24/123 > > Signed-off-by: Loic Poulain <loic.poulain@xxxxxxxxxx> > Loic Poulain: - fixed driver remove / clk deregistering > - Removed useless memory barriers > - devm usage when possible > - Fixed Kconfig depends > --- Applied to clk-next
