[PATCH v15 10/15] pmdomain: rockchip: cycle an optional power-domain reset on power-on

[Jiaxing Hu <gahing@gahingwoo.com>]

Some Rockchip domains come out of power-on with their bus interface in an
undefined state. On the RK3576 NPU this shows up as a hang on the first
register access after the domain is switched on, and pulsing the domain's
reset at this point clears it.

Take the domain node's reset if it has one, and pulse it between
releasing idle and restoring QoS. The reset is optional, so domains that
do not list one are unaffected.

Signed-off-by: Jiaxing Hu <gahing@gahingwoo.com>
Reviewed-by: Abel Vesa <abel.vesa@oss.qualcomm.com>
---
 drivers/pmdomain/rockchip/pm-domains.c | 33 +++++++++++++++++++++++++-
 1 file changed, 32 insertions(+), 1 deletion(-)

diff --git a/drivers/pmdomain/rockchip/pm-domains.c b/drivers/pmdomain/rockchip/pm-domains.c
index e3cc60fa2277..0f4ea5471792 100644
--- a/drivers/pmdomain/rockchip/pm-domains.c
+++ b/drivers/pmdomain/rockchip/pm-domains.c
@@ -19,6 +19,7 @@
 #include <linux/of_clk.h>
 #include <linux/clk.h>
 #include <linux/delay.h>
+#include <linux/reset.h>
 #include <linux/regmap.h>
 #include <linux/regulator/consumer.h>
 #include <linux/mfd/syscon.h>
@@ -103,6 +104,7 @@ struct rockchip_pm_domain {
 	struct clk_bulk_data *clks;
 	struct device_node *node;
 	struct regulator *supply;
+	struct reset_control *reset;
 };
 
 struct rockchip_pmu {
@@ -688,6 +690,21 @@ static int rockchip_pd_power(struct rockchip_pm_domain *pd, bool power_on)
 		if (ret < 0)
 			goto out;
 
+		/*
+		 * Optional: some domains need their reset cycled once power
+		 * is on. This goes BEFORE the settle delay, not after: a
+		 * domain that asks for both is asking to settle before the
+		 * QoS registers answer, and a reset deasserted after the
+		 * delay would leave nothing between it and the QoS writes.
+		 * On RK3576 the reset being cycled is the NPU core's bus
+		 * interface, which is what those writes go through.
+		 */
+		if (pd->reset) {
+			reset_control_assert(pd->reset);
+			usleep_range(10, 20);
+			reset_control_deassert(pd->reset);
+		}
+
 		/* Some domains need to settle before the QoS registers answer. */
 		if (pd->info->delay_us)
 			udelay(pd->info->delay_us);
@@ -873,6 +890,14 @@ static int rockchip_pm_add_one_domain(struct rockchip_pmu *pmu,
 	if (error)
 		goto err_put_clocks;
 
+	pd->reset = of_reset_control_get_optional_exclusive(node, NULL);
+	if (IS_ERR(pd->reset)) {
+		error = dev_err_probe(pmu->dev, PTR_ERR(pd->reset),
+				      "%pOFn: failed to get reset\n", node);
+		pd->reset = NULL;
+		goto err_unprepare_clocks;
+	}
+
 	pd->num_qos = of_count_phandle_with_args(node, "pm_qos",
 						 NULL);
 
@@ -943,11 +968,13 @@ static int rockchip_pm_add_one_domain(struct rockchip_pmu *pmu,
 	clk_bulk_unprepare(pd->num_clks, pd->clks);
 err_put_clocks:
 	clk_bulk_put(pd->num_clks, pd->clks);
+	reset_control_put(pd->reset);
 	return error;
 }
 
 static void rockchip_pm_remove_one_domain(struct rockchip_pm_domain *pd)
 {
+	struct reset_control *reset;
 	int ret;
 
 	/*
@@ -962,11 +989,15 @@ static void rockchip_pm_remove_one_domain(struct rockchip_pm_domain *pd)
 	clk_bulk_unprepare(pd->num_clks, pd->clks);
 	clk_bulk_put(pd->num_clks, pd->clks);
 
-	/* protect the zeroing of pm->num_clks */
+	/* protect the zeroing of pd->num_clks and pd->reset */
 	mutex_lock(&pd->pmu->mutex);
 	pd->num_clks = 0;
+	reset = pd->reset;
+	pd->reset = NULL;
 	mutex_unlock(&pd->pmu->mutex);
 
+	reset_control_put(reset);
+
 	/* devm will free our memory */
 }
 
-- 
2.43.0