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[0/3] cpufreq: sama7g5: add support for sama7g5

Message ID 1609842147-8161-1-git-send-email-claudiu.beznea@microchip.com
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Series cpufreq: sama7g5: add support for sama7g5 | expand

Message

Claudiu Beznea Jan. 5, 2021, 10:22 a.m. UTC 
Hi,

SAMA7G5 supports run-time changes of CPU frequency. This is done by
changing CPU's PLL. The block diagram explaining the relation b/w
CPU clock and its PLL is as follows:

                         +--------------> cpuck
                         |
               +------+  |    +-----+
  cpupllck --> | pres |--+--> | div |---> mck
               +------+       +-----+

where cpuck is the CPU's clock and mck is the system master clock 0
that feeds some other IPs. All the IPs feed by mck are glich free 
aware.

Because MCK is also feed by cpuplllk the CPUFreq driver needs also
to handle this clock to avoid its under/over clocking: every
time the CPUFreq's .target_index API is called:
- the mck frequency is adjusted to avoid its overclocking/underclocking
- then the cpuck frequency is increased/lowered
- then mck frequency is adjusted to keep the initial 200MHz frequency

Thank you,
Claudiu Beznea

Claudiu Beznea (3):
  dt-bindings: cpufreq: sama7g5-cpufreq: add dt bindings documentation
  cpufreq: sama7g5: add cpufreq driver
  MAINTAINERS: add sama7g5 cpufreq

 .../bindings/cpufreq/cpufreq-sama7g5.yaml          |  80 +++++
 MAINTAINERS                                        |   6 +
 drivers/cpufreq/Kconfig.arm                        |   9 +
 drivers/cpufreq/Makefile                           |   1 +
 drivers/cpufreq/cpufreq-dt-platdev.c               |   2 +
 drivers/cpufreq/sama7g5-cpufreq.c                  | 371 +++++++++++++++++++++
 6 files changed, 469 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/cpufreq/cpufreq-sama7g5.yaml
 create mode 100644 drivers/cpufreq/sama7g5-cpufreq.c