clocksource/drivers/msc313e: Add support for ssd20xd-based platforms

On SSD20X family SoCs the timers are connected to a 432MHz clock instead
of 12MHz that all the previous chips used. There is no way to reduce or
divide these clocks in the clktree yet as we do not know exactly where
the 432MHz clock comes from but it is enabled at boot.

The SSD20X timers have an input clock divider within the timer itself
to configure the frequency. timer0 is preconfigured at power up to run
at 12MHz so it is backwards compatible and doesn't need special handling
right now. timer1 and timer2 run at 432Mhz at power up so are not
backward compatible.

This commit adds support for the input clock divider register and sets
timer1 and timer2 to run at 48Mhz for clockevents.

Signed-off-by: Romain Perier <romain.perier@gmail.com>
Link: https://lore.kernel.org/r/20211217195727.8955-3-romain.perier@gmail.com
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

diff --git a/drivers/clocksource/timer-msc313e.c b/drivers/clocksource/timer-msc313e.c
index 154e73444a0c04bd1cd168e4fc09ef7f1a829d4f..54c54ca7c7869f7812e61655f339b8da178c4e9b 100644 (file)
--- a/drivers/clocksource/timer-msc313e.c
+++ b/drivers/clocksource/timer-msc313e.c
@@ -33,7 +33,9 @@
 #define MSC313E_REG_TIMER_MAX_HIGH     0x0c
 #define MSC313E_REG_COUNTER_LOW                0x10
 #define MSC313E_REG_COUNTER_HIGH       0x14
+#define MSC313E_REG_TIMER_DIVIDE       0x18
 
+#define MSC313E_CLK_DIVIDER            9
 #define TIMER_SYNC_TICKS               3
 
 #ifdef CONFIG_ARM
@@ -179,6 +181,12 @@ static int __init msc313e_clkevt_init(struct device_node *np)
        if (ret)
                return ret;
 
+       if (of_device_is_compatible(np, "sstar,ssd20xd-timer")) {
+               to->of_clk.rate = clk_get_rate(to->of_clk.clk) / MSC313E_CLK_DIVIDER;
+               to->of_clk.period = DIV_ROUND_UP(to->of_clk.rate, HZ);
+               writew(MSC313E_CLK_DIVIDER - 1, timer_of_base(to) + MSC313E_REG_TIMER_DIVIDE);
+       }
+
        msc313e_clkevt.cpumask = cpu_possible_mask;
        msc313e_clkevt.irq = to->of_irq.irq;
        to->clkevt = msc313e_clkevt;
@@ -242,3 +250,4 @@ static int __init msc313e_timer_init(struct device_node *np)
 }
 
 TIMER_OF_DECLARE(msc313, "mstar,msc313e-timer", msc313e_timer_init);
+TIMER_OF_DECLARE(ssd20xd, "sstar,ssd20xd-timer", msc313e_timer_init);