On 1/6/25 9:33 AM, Tudor Ambarus wrote:

Hi, Krzysztof,

On 12/31/24 2:32 PM, Tudor Ambarus wrote:

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diff --git a/drivers/firmware/samsung/Kconfig b/drivers/firmware/samsung/Kconfig
new file mode 100644
index 000000000000..750b41342174
--- /dev/null
+++ b/drivers/firmware/samsung/Kconfig

@@ -0,0 +1,14 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+config EXYNOS_ACPM_PROTOCOL
+	tristate "Exynos Alive Clock and Power Manager (ACPM) Message Protocol"
+	depends on ARCH_EXYNOS || COMPILE_TEST
+	depends on EXYNOS_MBOX

Is it build time dependency? No || COMPILE_TEST?

There's no build time dependency, I'll drop this line.

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Is it fine when EXYNOS_MBOX is a module?

Yes. When the EXYNOS_MBOX module is not loaded, and one tries to load
EXYNOS_ACPM_PROTOCOL module, the later will defer probe when requesting
the mailbox channels, but that's fine.

I'll need to select EXYNOS_MBOX, I explain why below.

cut

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+ */
+static const struct acpm_handle *acpm_get_by_phandle(struct device_node *np,
+						     const char *property)
+{
+	struct acpm_handle *handle = NULL;
+	struct device_node *acpm_np;
+	struct acpm_info *info;
+
+	if (!np) {
+		pr_err("I need a device pointer\n");
+		return ERR_PTR(-EINVAL);
+	}
+
+	acpm_np = of_parse_phandle(np, property, 0);
+	if (!acpm_np)
+		return ERR_PTR(-ENODEV);
+
+	mutex_lock(&acpm_list_mutex);
+	list_for_each_entry(info, &acpm_list, node) {
+		if (acpm_np == info->dev->of_node) {
+			handle = &info->handle;
+			info->users++;
+			break;
+		}
+	}
+	mutex_unlock(&acpm_list_mutex);
+	of_node_put(acpm_np);
+

You also need device links and probably try_module_get. See clk.c

I find these necessary too, will add them. try_module_get() must be
called when the module exists and is alive, otherwise I get a NULL ptr
dereference. I need a module dependency between acpm-protocol.ko and
exynos-mailbox.ko.
	select EXYNOS_MBOX and
	MODULE_SOFTDEP("pre: exynos-mailbox");
shall do the trick I think.

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clk_hw_create_clk() or of_qcom_ice_get(). Interestingly, none of them
perform both operations, which I think is necessary.

I think you could also avoid entire list and mutex by using
platform_get_drvdata(), see of_qcom_ice_get().

Using platform_get_drvdata() will simplify the code, thanks. It still
assumes the platform driver exists and is alive, otherwise we get a NULL
ptr dereference when getting the drvdata. But we'll be safe if I add the
module dependency.

Ah, MODULE_SOFTDEP is a soft dependency, so I can't use
platform_get_drvdata(), because if someone removes the exynos-mailbox.ko
from the file system for example, the acpm protocol will defer and its
clients still get a NULL ptr dereference when trying to get the handle
(where try_module_get() and platform_get_drvdata() are called). I'm
better off with the list and mutex.