linux-kernel - [PATCH] of: property: do not create clocks device link for clock controllers

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Date:   Thu, 25 Nov 2021 21:36:22 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>
Cc:     linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Saravana Kannan <saravanak@...gle.com>
Subject: [PATCH] of: property: do not create clocks device link for clock controllers

Do not create device link for clock controllers. Some of the clocks
provided to the device via OF can be the clocks that are just parents to
the clocks provided by this clock controller. Clock subsystem already
has support for handling missing clock parents correctly (clock
orphans). Later when the parent clock is registered, clocks get
populated properly.

An example of the system where this matters is the SDM8450 MTP board
(see arch/arm64/boot/dts/qcom/sdm845-mtp.dts). Here the dispcc uses
clocks provided by dsi0_phy and dsi1_phy device tree nodes. However the
dispcc itself provides clocks to both PHYs, to the PHY parent device,
etc. With just dsi0_phy in place devlink is able to break the
dependency, but with two PHYs, dispcc doesn't get probed at all, thus
breaking display support.

Cc: Bjorn Andersson <bjorn.andersson@...aro.org>
Cc: Stephen Boyd <swboyd@...omium.org>
Cc: Saravana Kannan <saravanak@...gle.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
---
 drivers/of/property.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/of/property.c b/drivers/of/property.c
index a3483484a5a2..f7229e4030e3 100644
--- a/drivers/of/property.c
+++ b/drivers/of/property.c
@@ -1264,7 +1264,6 @@ struct supplier_bindings {
 	bool node_not_dev;
 };
 
-DEFINE_SIMPLE_PROP(clocks, "clocks", "#clock-cells")
 DEFINE_SIMPLE_PROP(interconnects, "interconnects", "#interconnect-cells")
 DEFINE_SIMPLE_PROP(iommus, "iommus", "#iommu-cells")
 DEFINE_SIMPLE_PROP(mboxes, "mboxes", "#mbox-cells")
@@ -1294,6 +1293,21 @@ DEFINE_SIMPLE_PROP(backlight, "backlight", NULL)
 DEFINE_SUFFIX_PROP(regulators, "-supply", NULL)
 DEFINE_SUFFIX_PROP(gpio, "-gpio", "#gpio-cells")
 
+static struct device_node *parse_clocks(struct device_node *np,
+					const char *prop_name, int index)
+{
+	/*
+	 * Do not create clock-related device links for clocks controllers,
+	 * clock orphans will handle missing clock parents automatically.
+	 */
+	if (!strcmp(prop_name, "clocks") &&
+	    of_find_property(np, "#clock-cells", NULL))
+		return NULL;
+
+	return parse_prop_cells(np, prop_name, index, "clocks",
+				       "#clock-cells");
+}
+
 static struct device_node *parse_gpios(struct device_node *np,
 				       const char *prop_name, int index)
 {
-- 
2.33.0