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SAM9X60's PLL which is also part of SAMA7G5 is composed of 2 parts:
one fractional part and one divider. On SAMA7G5 the CPU PLL could be
changed at run-time to implement DVFS. The hardware clock tree on
SAMA7G5 for CPU PLL is as follows:
+---- div1 ----------------> cpuck
|
FRAC PLL ---> DIV PLL -+-> prescaler ---> div0 ---> mck0
The div1 block is not implemented in Linux; on prescaler block it has
been discovered a bug on some scenarios and will be removed from Linux
in next commits. Thus, the final clock tree that will be used in Linux
will be as follows:
+-----------> cpuck
|
FRAC PLL ---> DIV PLL -+-> div0 ---> mck0
It has been proposed in [1] to not introduce a new CPUFreq driver but
to overload the proper clock drivers with proper operation such that
cpufreq-dt to be used. To accomplish this DIV PLL and div0 implement
clock notifiers which applies safe dividers before FRAC PLL is changed.
The current commit treats only the DIV PLL by adding a notifier that
sets a safe divider on PRE_RATE_CHANGE events. The safe divider is
provided by initialization clock code (sama7g5.c). The div0 is treated
in next commits (to keep the changes as clean as possible).
[1] https://lore.kernel.org/lkml/20210105104426.4tmgc2l3vyicwedd@vireshk-i7/
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20211011112719.3951784-12-claudiu.beznea@microchip.com
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
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| .. | ||
| at91rm9200.c | ||
| at91sam9g45.c | ||
| at91sam9n12.c | ||
| at91sam9rl.c | ||
| at91sam9x5.c | ||
| at91sam9260.c | ||
| clk-audio-pll.c | ||
| clk-generated.c | ||
| clk-h32mx.c | ||
| clk-i2s-mux.c | ||
| clk-main.c | ||
| clk-master.c | ||
| clk-peripheral.c | ||
| clk-pll.c | ||
| clk-plldiv.c | ||
| clk-programmable.c | ||
| clk-sam9x60-pll.c | ||
| clk-slow.c | ||
| clk-smd.c | ||
| clk-system.c | ||
| clk-usb.c | ||
| clk-utmi.c | ||
| dt-compat.c | ||
| Makefile | ||
| pmc.c | ||
| pmc.h | ||
| sam9x60.c | ||
| sama5d2.c | ||
| sama5d3.c | ||
| sama5d4.c | ||
| sama7g5.c | ||
| sckc.c | ||