libpayload: timer: Revert timer_hz() return type to 64-bits

It seems that reducing the return type of timer_hz() to uint32_t in
CB:78888 was a bad idea... some Intel platforms actually use their raw
CPU clock for the timestamp counter which can be higher than 4GHz. This
patch reverts it back to uint64_t.

Also remove the redundant assertion in timer/generic.c since timer_us()
itself already does that check.

Cq-Depend: chromium:5274555
Change-Id: I471c7de7a28aec5bb965b23525ed579481ac8361
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/80320
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Yidi Lin <yidilin@google.com>

payloads/libpayload/drivers/timer/arm64_arch_timer.c

@@ -32,7 +32,7 @@
 #include <arch/lib_helpers.h>
 #include <libpayload.h>
 
-uint32_t timer_hz(void)
+uint64_t timer_hz(void)
 {
 	return raw_read_cntfrq_el0();
 }

payloads/libpayload/drivers/timer/generic.c

@@ -33,10 +33,8 @@
 #include <assert.h>
 #include <libpayload.h>
 
-uint32_t timer_hz(void)
+uint64_t timer_hz(void)
 {
-	/* libc/time.c currently requires all timers to be at least 1MHz. */
-	assert(CONFIG_LP_TIMER_GENERIC_HZ >= 1000000);
 	return CONFIG_LP_TIMER_GENERIC_HZ;
 }
 

payloads/libpayload/drivers/timer/rdtsc.c

@@ -35,10 +35,9 @@
 #include <arch/rdtsc.h>
 #include <assert.h>
 
-uint32_t timer_hz(void)
+uint64_t timer_hz(void)
 {
-	assert(UINT32_MAX / 1000 >= lib_sysinfo.cpu_khz);
+	return (uint64_t)lib_sysinfo.cpu_khz * 1000;
-	return lib_sysinfo.cpu_khz * 1000;
 }
 
 uint64_t timer_raw_value(void)

payloads/libpayload/include/libpayload.h

@@ -519,7 +519,7 @@ void lib_sysinfo_get_memranges(struct memrange **ranges,
 
 /* Timer functions. */
 /* Defined by each architecture. */
-uint32_t timer_hz(void);
+uint64_t timer_hz(void);
 uint64_t timer_raw_value(void);
 uint64_t timer_us(uint64_t base);
 /* Generic. */

payloads/libpayload/libc/time.c

@@ -171,14 +171,15 @@ void arch_ndelay(uint64_t ns)
 
 u64 timer_us(u64 base)
 {
-	static u32 hz, mult = USECS_PER_SEC;
+	static u64 hz;
+	static u32 mult = USECS_PER_SEC;
 	u32 div;
 
 	// Only check timer_hz once. Assume it doesn't change.
 	if (hz == 0) {
 		hz = timer_hz();
 		if (hz < mult) {
-			printf("Timer frequency %" PRIu32 " is too low, "
+			printf("Timer frequency %" PRIu64 " is too low, "
 			       "must be at least 1MHz.\n", hz);
 			halt();
 		}