clk: qcom: Add CPU clock driver for msm8996

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 <[email protected]>
Rajendra Nayak: Initial RFC - https://lkml.org/lkml/2016/9/29/84

Signed-off-by: Ilia Lin <[email protected]>
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 <[email protected]>
Loic Poulain: - fixed driver remove / clk deregistering
              - Removed useless memory barriers
              - devm usage when possible
              - Fixed Kconfig depends

Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Stephen Boyd <[email protected]>

Author: Loic Poulain

drivers/clk/qcom/Kconfig

@@ -37,6 +37,15 @@ config QCOM_CLK_APCS_MSM8916
 	  Say Y if you want to support CPU frequency scaling on devices
 	  such as msm8916.
 
+config QCOM_CLK_APCC_MSM8996
+	tristate "MSM8996 CPU Clock Controller"
+	select QCOM_KRYO_L2_ACCESSORS
+	depends on ARM64
+	help
+	  Support for the CPU clock controller on msm8996 devices.
+	  Say Y if you want to support CPU clock scaling using CPUfreq
+	  drivers for dyanmic power management.
+
 config QCOM_CLK_RPM
 	tristate "RPM based Clock Controller"
 	depends on MFD_QCOM_RPM

drivers/clk/qcom/Makefile

@@ -44,6 +44,7 @@ obj-$(CONFIG_MSM_MMCC_8996) += mmcc-msm8996.o
 obj-$(CONFIG_MSM_MMCC_8998) += mmcc-msm8998.o
 obj-$(CONFIG_QCOM_A53PLL) += a53-pll.o
 obj-$(CONFIG_QCOM_CLK_APCS_MSM8916) += apcs-msm8916.o
+obj-$(CONFIG_QCOM_CLK_APCC_MSM8996) += clk-cpu-8996.o
 obj-$(CONFIG_QCOM_CLK_RPM) += clk-rpm.o
 obj-$(CONFIG_QCOM_CLK_RPMH) += clk-rpmh.o
 obj-$(CONFIG_QCOM_CLK_SMD_RPM) += clk-smd-rpm.o

drivers/clk/qcom/clk-alpha-pll.h

@@ -47,6 +47,12 @@ struct pll_vco {
 	u32 val;
 };
 
+#define VCO(a, b, c) { \
+	.val = a,\
+	.min_freq = b,\
+	.max_freq = c,\
+}
+
 /**
  * struct clk_alpha_pll - phase locked loop (PLL)
  * @offset: base address of registers