[PATCH v3 1/2] lib: utils/timer: mtimer: Select the reference mtimer from a DT property

[Benoît Monin]

The current selection of the reference MTIMER may fail in some setup.
In a multi-cluster configuration, there is one MTIMER per cluster, each
associated with the HARTS of the cluster. So we do not have a MTIMER
with no associated HARTs to use as our reference.

To be able to select a reference MTIMER in that case, look up an optional
device tree property named "riscv,reference-mtimer" that indicate which
MTIMER is the reference.

Signed-off-by: Benoît Monin <benoit.monin at bootlin.com>
---
 lib/utils/timer/fdt_timer_mtimer.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/lib/utils/timer/fdt_timer_mtimer.c b/lib/utils/timer/fdt_timer_mtimer.c
index e1fd0519..1f29f3a2 100644
--- a/lib/utils/timer/fdt_timer_mtimer.c
+++ b/lib/utils/timer/fdt_timer_mtimer.c
@@ -39,6 +39,7 @@ static int timer_mtimer_cold_init(const void *fdt, int nodeoff,
 	struct aclint_mtimer_data *mt;
 	const struct timer_mtimer_quirks *quirks = match->data;
 	bool is_clint = quirks && quirks->is_clint;
+	bool is_ref = false;
 
 	mtn = sbi_zalloc(sizeof(*mtn));
 	if (!mtn)
@@ -110,13 +111,16 @@ static int timer_mtimer_cold_init(const void *fdt, int nodeoff,
 	}
 
 	/*
-	 * Select first MTIMER device with no associated HARTs as our
-	 * reference MTIMER device. This is only a temporary strategy
-	 * of selecting reference MTIMER device. In future, we might
-	 * define an optional DT property or some other mechanism to
-	 * help us select the reference MTIMER device.
+	 * If we have a DT property to indicate which MTIMER is the reference,
+	 * select the first MTIMER device that has it. Otherwise, select the
+	 * first MTIMER device with no associated HARTs as our reference.
 	 */
-	if (!mt->hart_count && !mt_reference) {
+	if (fdt_getprop(fdt, nodeoff, "riscv,reference-mtimer", NULL))
+		is_ref = true;
+	else if (!mt->hart_count)
+		is_ref = true;
+
+	if (is_ref && !mt_reference) {
 		mt_reference = mt;
 		/*
 		 * Set reference for already propbed MTIMER devices

-- 
2.51.1