[RFC PATCH v2 3/8] pmdomain/rockchip: cycle optional power-domain resets on power-on

[Jiaxing Hu <gahing@gahingwoo.com>]

Some power domains contain hardware bus interfaces that require an
explicit assert/deassert edge on their reset line after the domain is
powered on.  The CRU preserves reset state across power cycles (stays
deasserted), so the hardware never sees the edge it needs unless the
driver pulses it explicitly.

Add an optional resets property to rockchip_pm_domain.  When present,
the resets are asserted and deasserted (with a 10 us hold) inside
rockchip_pd_power() after the idle bits are cleared and the delay_us
settling time has elapsed, but before any device in the domain resumes.
The resets are released in rockchip_pm_remove_one_domain().

Signed-off-by: Jiaxing Hu <gahing@gahingwoo.com>
---
 drivers/pmdomain/rockchip/pm-domains.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/drivers/pmdomain/rockchip/pm-domains.c b/drivers/pmdomain/rockchip/pm-domains.c
index 1787f62ba..8ce0cc3de 100644
--- a/drivers/pmdomain/rockchip/pm-domains.c
+++ b/drivers/pmdomain/rockchip/pm-domains.c
@@ -18,6 +18,7 @@
 #include <linux/of_address.h>
 #include <linux/of_clk.h>
 #include <linux/clk.h>
+#include <linux/reset.h>
 #include <linux/regmap.h>
 #include <linux/regulator/consumer.h>
 #include <linux/mfd/syscon.h>
@@ -102,6 +103,7 @@ struct rockchip_pm_domain {
 	struct clk_bulk_data *clks;
 	struct device_node *node;
 	struct regulator *supply;
+	struct reset_control *resets;
 };
 
 struct rockchip_pmu {
@@ -671,6 +673,12 @@ static int rockchip_pd_power(struct rockchip_pm_domain *pd, bool power_on)
 		if (pd->info->delay_us)
 			udelay(pd->info->delay_us);
 
+		if (pd->resets) {
+			reset_control_assert(pd->resets);
+			udelay(10);
+			reset_control_deassert(pd->resets);
+		}
+
 		rockchip_pmu_restore_qos(pd);
 	}
 
@@ -840,6 +848,14 @@ static int rockchip_pm_add_one_domain(struct rockchip_pmu *pmu,
 	if (error)
 		goto err_put_clocks;
 
+	pd->resets = of_reset_control_array_get_optional_exclusive(node);
+	if (IS_ERR(pd->resets)) {
+		error = PTR_ERR(pd->resets);
+		dev_err(pmu->dev, "%pOFn: failed to get resets: %d\n", node, error);
+		pd->resets = NULL;
+		goto err_unprepare_clocks;
+	}
+
 	pd->num_qos = of_count_phandle_with_args(node, "pm_qos",
 						 NULL);
 
@@ -910,6 +926,7 @@ 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->resets);
 	return error;
 }
 
@@ -928,6 +945,7 @@ 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);
+	reset_control_put(pd->resets);
 
 	/* protect the zeroing of pm->num_clks */
 	mutex_lock(&pd->pmu->mutex);
-- 
2.43.0