linux-kernel - [PATCH] clocksource/drivers/renesas-ostm: Avoid reprobe after successful early probe

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Message-Id: <bd027379713cbaafa21ffe9e848ebb7f475ca0e7.1710930542.git.geert+renesas@glider.be>
Date: Wed, 20 Mar 2024 11:30:07 +0100
From: Geert Uytterhoeven <geert+renesas@...der.be>
To: Daniel Lezcano <daniel.lezcano@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Saravana Kannan <saravanak@...gle.com>,
	Biju Das <biju.das.jz@...renesas.com>,
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Cc: 周琰杰 <zhouyanjie@...yeetech.com>,
	Paul Cercueil <paul@...pouillou.net>,
	Liviu Dudau <liviu.dudau@....com>,
	Sudeep Holla <sudeep.holla@....com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	linux-renesas-soc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Geert Uytterhoeven <geert+renesas@...der.be>
Subject: [PATCH] clocksource/drivers/renesas-ostm: Avoid reprobe after successful early probe

The Renesas OS Timer (OSTM) driver contains two probe points, of which
only one should complete:
  1. Early probe, using TIMER_OF_DECLARE(), to provide the sole
     clocksource on (arm32) RZ/A1 and RZ/A2 SoCs,
  2. Normal probe, using a platform driver, to provide additional timers
     on (arm64 + riscv) RZ/G2L and similar SoCs.

The latter is needed because using OSTM on RZ/G2L requires manipulation
of its reset signal, which is not yet available at the time of early
probe, causing early probe to fail with -EPROBE_DEFER.  It is only
enabled when building a kernel with support for the RZ/G2L family, so it
does not impact RZ/A1 and RZ/A2.  Hence only one probe method can
complete on all affected systems.

As relying on the order of initialization of subsystems inside the
kernel is fragile, set the DT node's OF_POPULATED flag after a succesful
early probe.  This makes sure the platform driver's probe is never
called after a successful early probe.

Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
---
Tested on RZ/A2 (after force-enabling the platform driver probe).
Regression-tested on RZ/Five (member of the RZ/G2L family).

In between commit 4f41fe386a94639c ("clocksource/drivers/timer-probe:
Avoid creating dead devices") and its revert 4479730e9263befb (both in
v5.7), the clocksource core took care of this.  Other subsystems[1]
still handle this, either minimally (by just setting OF_POPULATED), or
fully (by also clearing OF_POPULATED again in case of probe failure).

Note that despite the revert in the clocksource core, several
clocksource drivers[2] still clear the OF_POPULATED flag manually, to
force probing the same device using both TIMER_OF_DECLARE() and standard
platform device probing (the latter may be done in a different driver).

[1] See of_clk_init(), of_gpiochip_scan_gpios(), of_irq_init().
[2] drivers/clocksource/ingenic-sysost.c
    drivers/clocksource/ingenic-timer.c
    drivers/clocksource/timer-versatile.c
---
 drivers/clocksource/renesas-ostm.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/clocksource/renesas-ostm.c b/drivers/clocksource/renesas-ostm.c
index 8da972dc171365bc..37db7e23a4d29135 100644
--- a/drivers/clocksource/renesas-ostm.c
+++ b/drivers/clocksource/renesas-ostm.c
@@ -210,6 +210,7 @@ static int __init ostm_init(struct device_node *np)
 		pr_info("%pOF: used for clock events\n", np);
 	}

+	of_node_set_flag(np, OF_POPULATED);
 	return 0;

 err_cleanup:
-- 
2.34.1