linux-kernel - [PATCH] clock: mediatek: mt8173: Handle unallocated infracfg clock data

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Date:   Thu,  9 Nov 2023 00:33:43 +0300
From:   Alper Nebi Yasak <alpernebiyasak@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>, Stephen Boyd <sboyd@...nel.org>,
        linux-clk@...r.kernel.org, Chen-Yu Tsai <wenst@...omium.org>,
        linux-arm-kernel@...ts.infradead.org,
        Michael Turquette <mturquette@...libre.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        linux-mediatek@...ts.infradead.org,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Alper Nebi Yasak <alpernebiyasak@...il.com>
Subject: [PATCH] clock: mediatek: mt8173: Handle unallocated infracfg clock data

The MT8173 infracfg clock driver does initialization in two steps, via a
CLK_OF_DECLARE_DRIVER declaration. However its early init function
doesn't get to run when it's built as a module, presumably since it's
not loaded by the time it would have been called by of_clk_init(). This
causes its second-step probe() to return -ENOMEM when trying to register
clocks, as the necessary clock_data struct isn't initialized by the
first step.

MT2701 and MT6797 clock drivers also use this mechanism, but they try to
allocate the necessary clock_data structure if missing in the second
step. Mimic that for the MT8173 infracfg clock as well to make it work
as a module.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@...il.com>
---
I've tried adding cpumux support to clk-mtk.c then switching this over
to simple probe functions and it appears to work for me, though I don't
know clock systems enough to recognize if it's subtly broken instead.
That'd remove this piece of code, but this might still be worth applying
to backport to stable kernels.

If I'm reading things correctly, it looks like it would be possible to
add cpumux & pll & pllfh support to clk-mtk.c, then move most if not
every driver to simple probe, with one file per clock and module
support. How much of that is desirable? In what order do the parts need
to be registered?

 drivers/clk/mediatek/clk-mt8173-infracfg.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/mediatek/clk-mt8173-infracfg.c b/drivers/clk/mediatek/clk-mt8173-infracfg.c
index 2f2f074e231a..ecc8b0063ea5 100644
--- a/drivers/clk/mediatek/clk-mt8173-infracfg.c
+++ b/drivers/clk/mediatek/clk-mt8173-infracfg.c
@@ -98,7 +98,17 @@ CLK_OF_DECLARE_DRIVER(mtk_infrasys, "mediatek,mt8173-infracfg",
 static int clk_mt8173_infracfg_probe(struct platform_device *pdev)
 {
 	struct device_node *node = pdev->dev.of_node;
-	int r;
+	int r, i;
+
+	if (!infra_clk_data) {
+		infra_clk_data = mtk_alloc_clk_data(CLK_INFRA_NR_CLK);
+		if (!infra_clk_data)
+			return -ENOMEM;
+	} else {
+		for (i = 0; i < CLK_INFRA_NR_CLK; i++)
+			if (infra_clk_data->hws[i] == ERR_PTR(-EPROBE_DEFER))
+				infra_clk_data->hws[i] = ERR_PTR(-ENOENT);
+	}

 	r = mtk_clk_register_gates(&pdev->dev, node, infra_gates,
 				   ARRAY_SIZE(infra_gates), infra_clk_data);

base-commit: 2220f68f4504aa1ccce0fac721ccdb301e9da32f
-- 
2.42.0