linux-kernel - [PATCH 2/2] of: property: fw_devlink: Set 'optional_con_dev' for parse_power

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Date:   Tue, 31 Aug 2021 12:21:41 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Saravana Kannan <saravanak@...gle.com>,
        Rob Herring <robh@...nel.org>, devicetree@...r.kernel.org
Cc:     "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Stephen Boyd <sboyd@...nel.org>,
        Dmitry Osipenko <digetx@...il.com>,
        Ulf Hansson <ulf.hansson@...aro.org>, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: [PATCH 2/2] of: property: fw_devlink: Set 'optional_con_dev' for parse_power_domains

The power-domain DT bindings [1] doesn't enforce a compatible string for a
provider node, even if this is common to use. In particular, when
describing a hierarchy with parent/child power-domains, as the psci DT
bindings [2] for example, it's sometimes not applicable to use a compatible
string.

Therefore, let's set the 'optional_con_dev' to true to avoid creating
incorrect fw_devlinks for power-domains.

[1] Documentation/devicetree/bindings/power/power-domain.yaml
[2] Documentation/devicetree/bindings/arm/psci.yaml

Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
---

Some more details of what goes on here. I have added a debug print in
of_link_to_phandle() to see the fw_devlinks that gets created.

This is what happens on Dragonboard 410c when 'optional_con_dev' isn't set:
...
[    0.041274] device: 'psci': device_add
[    0.041366] OF: Linking power-domain-cpu0 (consumer) to psci (supplier)
[    0.041395] OF: Linking power-domain-cpu1 (consumer) to psci (supplier)
[    0.041423] OF: Linking power-domain-cpu2 (consumer) to psci (supplier)
[    0.041451] OF: Linking power-domain-cpu3 (consumer) to psci (supplier)
[    0.041494] device: 'platform:psci--platform:psci': device_add
[    0.041556] platform psci: Linked as a sync state only consumer to psci
...

This is what happens on Dragonboard 410c when 'optional_con_dev' is set:
...
[    0.041179] device: 'psci': device_add
[    0.041265] OF: Not linking psci to psci - is descendant
[    0.041293] OF: Not linking psci to psci - is descendant
[    0.041319] OF: Not linking psci to psci - is descendant
[    0.041346] OF: Not linking psci to psci - is descendant
...

The relevant dtsi file:
arch/arm64/boot/dts/qcom/msm8916.dtsi

Kind regards
Ulf Hansson

---
 drivers/of/property.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/of/property.c b/drivers/of/property.c
index 2babb1807228..4d607fdbea24 100644
--- a/drivers/of/property.c
+++ b/drivers/of/property.c
@@ -1356,7 +1356,7 @@ static const struct supplier_bindings of_supplier_bindings[] = {
 	{ .parse_prop = parse_io_channels, },
 	{ .parse_prop = parse_interrupt_parent, },
 	{ .parse_prop = parse_dmas, .optional = true, },
-	{ .parse_prop = parse_power_domains, },
+	{ .parse_prop = parse_power_domains, .optional_con_dev = true, },
 	{ .parse_prop = parse_hwlocks, },
 	{ .parse_prop = parse_extcon, },
 	{ .parse_prop = parse_nvmem_cells, },
-- 
2.25.1