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From:   Maxime Ripard <maxime@cerno.tech>
Date:   Tue, 04 Apr 2023 12:11:55 +0200
Subject: [PATCH v3 65/65] clk: Forbid to register a mux without
 determine_rate
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Message-Id: <20221018-clk-range-checks-fixes-v3-65-9a1358472d52@cerno.tech>
References: <20221018-clk-range-checks-fixes-v3-0-9a1358472d52@cerno.tech>
In-Reply-To: <20221018-clk-range-checks-fixes-v3-0-9a1358472d52@cerno.tech>
To:     Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@kernel.org>,
        =?utf-8?q?Andreas_F=C3=A4rber?= <afaerber@suse.de>,
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        Kishon Vijay Abraham I <kishon@kernel.org>,
        Alessandro Zummo <a.zummo@towertech.it>,
        Chen-Yu Tsai <wens@csie.org>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
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        Liam Girdwood <lgirdwood@gmail.com>,
        Mark Brown <broonie@kernel.org>,
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Cc:     linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>,
        linux-arm-kernel@lists.infradead.org,
        linux-actions@lists.infradead.org, patches@opensource.cirrus.com,
        linux-stm32@st-md-mailman.stormreply.com,
        linux-mediatek@lists.infradead.org,
        linux-renesas-soc@vger.kernel.org, linux-tegra@vger.kernel.org,
        dri-devel@lists.freedesktop.org, linux-phy@lists.infradead.org,
        linux-rtc@vger.kernel.org, linux-sunxi@lists.linux.dev,
        alsa-devel@alsa-project.org, linux-mips@vger.kernel.org,
        Maxime Ripard <maxime@cerno.tech>
Precedence: bulk

The determine_rate hook allows to select the proper parent and its rate
for a given clock configuration. On another hand, set_parent is there to
change the parent of a mux.

Some clocks provide a set_parent hook but don't implement
determine_rate. In such a case, set_parent is pretty much useless since
the clock framework will always assume the current parent is to be used,
and we will thus never change it.

This situation can be solved in two ways:
  - either we don't need to change the parent, and we thus shouldn't
    implement set_parent;
  - or we don't want to change the parent, in this case we should set
    CLK_SET_RATE_NO_REPARENT;
  - or we're missing a determine_rate implementation.

The latter is probably just an oversight from the driver's author, and
we should thus raise their awareness about the fact that the current
state of the driver is confusing.

All the drivers in-tree have been converted by now, so let's prevent any
clock with set_parent but without determine_rate to register so that it
can't sneak in again in the future.

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
---
 drivers/clk/clk.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index f9fc8730ed17..4c1f28fb8c1f 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -3746,6 +3746,13 @@ static int __clk_core_init(struct clk_core *core)
 		goto out;
 	}
 
+	if (core->ops->set_parent && !core->ops->determine_rate) {
+		pr_err("%s: %s must implement .set_parent & .determine_rate\n",
+			__func__, core->name);
+		ret = -EINVAL;
+		goto out;
+	}
+
 	if (core->num_parents > 1 && !core->ops->get_parent) {
 		pr_err("%s: %s must implement .get_parent as it has multi parents\n",
 		       __func__, core->name);

-- 
2.39.2