linux-kernel - [PATCH v2 2/4] clk: keystone: don't cache clock rate

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Message-ID: <20251223124729.2482877-3-mwalle@kernel.org>
Date: Tue, 23 Dec 2025 13:47:14 +0100
From: Michael Walle <mwalle@...nel.org>
To: Frank Binns <frank.binns@...tec.com>,
	Matt Coster <matt.coster@...tec.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Nishanth Menon <nm@...com>,
	Vignesh Raghavendra <vigneshr@...com>,
	Tero Kristo <kristo@...nel.org>,
	Andrew Davis <afd@...com>,
	Santosh Shilimkar <ssantosh@...nel.org>,
	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...nel.org>,
	Kevin Hilman <khilman@...libre.com>,
	Randolph Sapp <rs@...com>
Cc: linux-clk@...r.kernel.org,
	dri-devel@...ts.freedesktop.org,
	devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Michael Walle <mwalle@...nel.org>
Subject: [PATCH v2 2/4] clk: keystone: don't cache clock rate

The TISCI firmware will return 0 if the clock or consumer is not
enabled although there is a stored value in the firmware. IOW a call to
set rate will work but at get rate will always return 0 if the clock is
disabled.
The clk framework will try to cache the clock rate when it's requested
by a consumer. If the clock or consumer is not enabled at that point,
the cached value is 0, which is wrong. Thus, disable the cache
altogether.

Signed-off-by: Michael Walle <mwalle@...nel.org>
Reviewed-by: Kevin Hilman <khilman@...libre.com>
Reviewed-by: Randolph Sapp <rs@...com>
---
 drivers/clk/keystone/sci-clk.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/clk/keystone/sci-clk.c b/drivers/clk/keystone/sci-clk.c
index 9d5071223f4c..0a1565fdbb3b 100644
--- a/drivers/clk/keystone/sci-clk.c
+++ b/drivers/clk/keystone/sci-clk.c
@@ -333,6 +333,14 @@ static int _sci_clk_build(struct sci_clk_provider *provider,
 
 	init.ops = &sci_clk_ops;
 	init.num_parents = sci_clk->num_parents;
+
+	/*
+	 * A clock rate query to the SCI firmware will return 0 if either the
+	 * clock itself is disabled or the attached device/consumer is disabled.
+	 * This makes it inherently unsuitable for the caching of the clk
+	 * framework.
+	 */
+	init.flags = CLK_GET_RATE_NOCACHE;
 	sci_clk->hw.init = &init;
 
 	ret = devm_clk_hw_register(provider->dev, &sci_clk->hw);
-- 
2.47.3