clk: qcom: add clock controller driver for qca8386/qca8084

The clock controller driver of qca8386/qca8084 is registered
as the MDIO device, the hardware register is accessed by MDIO bus
that is normally used to access general PHY device, which is
different from the current existed qcom clock controller drivers
using ioremap to access hardware clock registers, nsscc-qca8k is
accessed via an MDIO bus.

MDIO bus is commonly utilized by both qca8386/qca8084 and other
PHY devices, so the mutex lock mdio_bus->mdio_lock should be
used instead of using the mutex lock of remap.

To access the hardware clock registers of qca8386/qca8084, there
is a special MDIO frame sequence, which needs to be sent to the
device.

Enable the reference clock before resetting the clock controller,
the reference clock rate is fixed to 50MHZ.

Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Luo Jie <quic_luoj@quicinc.com>
Link: https://lore.kernel.org/r/20240605124541.2711467-5-quic_luoj@quicinc.com
Signed-off-by: Bjorn Andersson <andersson@kernel.org>

drivers/clk/qcom/Kconfig

@@ -249,6 +249,15 @@ config IPQ_GCC_9574
 	  i2c, USB, SD/eMMC, etc. Select this for the root clock
 	  of ipq9574.
 
+config IPQ_NSSCC_QCA8K
+	tristate "QCA8K(QCA8386 or QCA8084) NSS Clock Controller"
+	depends on MDIO_BUS || COMPILE_TEST
+	help
+	  Support for NSS(Network SubSystem) clock controller on
+	  qca8386/qca8084 chip.
+	  Say Y or M if you want to use network features of switch or
+	  PHY device. Select this for the root clock of qca8k.
+
 config MSM_GCC_8660
 	tristate "MSM8660 Global Clock Controller"
 	depends on ARM || COMPILE_TEST

drivers/clk/qcom/Makefile

@@ -36,6 +36,7 @@ obj-$(CONFIG_IPQ_GCC_806X) += gcc-ipq806x.o
 obj-$(CONFIG_IPQ_GCC_8074) += gcc-ipq8074.o
 obj-$(CONFIG_IPQ_GCC_9574) += gcc-ipq9574.o
 obj-$(CONFIG_IPQ_LCC_806X) += lcc-ipq806x.o
+obj-$(CONFIG_IPQ_NSSCC_QCA8K) += nsscc-qca8k.o
 obj-$(CONFIG_MDM_GCC_9607) += gcc-mdm9607.o
 obj-$(CONFIG_MDM_GCC_9615) += gcc-mdm9615.o
 obj-$(CONFIG_MSM_GCC_8660) += gcc-msm8660.o