[PATCH] clk: samsung: Revert "clk: Use device_get_match_data()"

[PATCH] clk: samsung: Revert "clk: Use device_get_match_data()"

[Marek Szyprowski]

device_get_match_data() function should not be used on the device other
than the one matched to the given driver, because it always returns the
match_data of the matched driver. In case of exynos-clkout driver, the
original code matches the OF IDs on the PARENT device, so replacing it
with of_device_get_match_data() broke the driver.

This has been already pointed once in commit 2bc5febd05ab ("clk: samsung:
Revert "clk: samsung: exynos-clkout: Use of_device_get_match_data()"").
To avoid further confusion, add a comment about this special case, which
requires direct of_match_device() call to pass custom IDs array.

This partially reverts commit 409c39ec92a35e3708f5b5798c78eae78512cd71.

Fixes: 409c39ec92a3 ("clk: Use device_get_match_data()")
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
---
 drivers/clk/samsung/clk-exynos-clkout.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/clk/samsung/clk-exynos-clkout.c b/drivers/clk/samsung/clk-exynos-clkout.c
index 3484e6cc80ad..503c6f5b20d5 100644
--- a/drivers/clk/samsung/clk-exynos-clkout.c
+++ b/drivers/clk/samsung/clk-exynos-clkout.c
@@ -13,9 +13,9 @@
 #include <linux/io.h>
 #include <linux/of.h>
 #include <linux/of_address.h>
+#include <linux/of_device.h>
 #include <linux/platform_device.h>
 #include <linux/pm.h>
-#include <linux/property.h>
 
 #define EXYNOS_CLKOUT_NR_CLKS		1
 #define EXYNOS_CLKOUT_PARENTS		32
@@ -84,17 +84,24 @@ MODULE_DEVICE_TABLE(of, exynos_clkout_ids);
 static int exynos_clkout_match_parent_dev(struct device *dev, u32 *mux_mask)
 {
 	const struct exynos_clkout_variant *variant;
+	const struct of_device_id *match;
 
 	if (!dev->parent) {
 		dev_err(dev, "not instantiated from MFD\n");
 		return -EINVAL;
 	}
 
-	variant = device_get_match_data(dev->parent);
-	if (!variant) {
+	/*
+	 * 'exynos_clkout_ids' arrays is not the ids array matched by
+	 * the dev->parent driver, so of_device_get_match_data() or
+	 * device_get_match_data() cannot be used here.
+	 */
+	match = of_match_device(exynos_clkout_ids, dev->parent);
+	if (!match) {
 		dev_err(dev, "cannot match parent device\n");
 		return -EINVAL;
 	}
+	variant = match->data;
 
 	*mux_mask = variant->mux_mask;
 
-- 
2.34.1


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Re: [PATCH] clk: samsung: Revert "clk: Use device_get_match_data()"

[Krzysztof Kozlowski]

On 25/04/2024 09:56, Marek Szyprowski wrote:
> device_get_match_data() function should not be used on the device other
> than the one matched to the given driver, because it always returns the
> match_data of the matched driver. In case of exynos-clkout driver, the
> original code matches the OF IDs on the PARENT device, so replacing it
> with of_device_get_match_data() broke the driver.
> 
> This has been already pointed once in commit 2bc5febd05ab ("clk: samsung:
> Revert "clk: samsung: exynos-clkout: Use of_device_get_match_data()"").
> To avoid further confusion, add a comment about this special case, which
> requires direct of_match_device() call to pass custom IDs array.
> 
> This partially reverts commit 409c39ec92a35e3708f5b5798c78eae78512cd71.

D'oh! Again!

But to be honest, I think there misleading code is that exynos-clkout
(so the child) has:
.of_match_table = exynos_clkout_ids,

So one really can believe that this driver matches to exynos_clkout_ids,
which are the same as exynos-pmu (parent).

I think we should drop the of_match_table and rely on driver name
matching (MFD cell) or platform_device_id.

This patch is correct, so above solution could be added as 2 patch.

Thanks for noticing it.

Best regards,
Krzysztof


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Re: [PATCH] clk: samsung: Revert "clk: Use device_get_match_data()"

[Krzysztof Kozlowski]

On Thu, 25 Apr 2024 09:56:28 +0200, Marek Szyprowski wrote:
> device_get_match_data() function should not be used on the device other
> than the one matched to the given driver, because it always returns the
> match_data of the matched driver. In case of exynos-clkout driver, the
> original code matches the OF IDs on the PARENT device, so replacing it
> with of_device_get_match_data() broke the driver.
> 
> This has been already pointed once in commit 2bc5febd05ab ("clk: samsung:
> Revert "clk: samsung: exynos-clkout: Use of_device_get_match_data()"").
> To avoid further confusion, add a comment about this special case, which
> requires direct of_match_device() call to pass custom IDs array.
> 
> [...]

Applied, thanks!

[1/1] clk: samsung: Revert "clk: Use device_get_match_data()"
      https://git.kernel.org/krzk/linux/c/da244c16ac58a3b1b7d8c54ec7780fd8326da2ff

Best regards,
-- 
Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>


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