From b1c37bec1ccfe5ccab72bc0ddc0dfa45c43e2de2 Mon Sep 17 00:00:00 2001
From: Miquel Raynal <miquel.raynal@bootlin.com>
Date: Tue, 4 Apr 2023 18:21:23 +0100
Subject: [PATCH] nvmem: core: request layout modules loading

When a storage device like an eeprom or an mtd device probes, it
registers an nvmem device if the nvmem subsystem has been enabled (bool
symbol). During nvmem registration, if the device is using layouts to
expose dynamic nvmem cells, the core will first try to get a reference
over the layout driver callbacks. In practice there is not relationship
that can be described between the storage driver and the nvmem
layout. So there is no way we can enforce both drivers will be built-in
or both will be modules. If the storage device driver is built-in but
the layout is built as a module, instead of badly failing with an
endless probe deferral loop, lets just make a modprobe call in case the
driver was made available in an initramfs with
of_device_node_request_module(), and offer a fully functional system to
the user.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Tested-by: Michael Walle <michael@walle.cc>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20230404172148.82422-16-srinivas.kandagatla@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/nvmem/core.c | 8 ++++++++
 1 file changed, 8 insertions(+)

--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -17,6 +17,7 @@
 #include <linux/nvmem-provider.h>
 #include <linux/gpio/consumer.h>
 #include <linux/of.h>
+#include <linux/of_device.h>
 #include <linux/slab.h>
 
 struct nvmem_device {
@@ -761,6 +762,13 @@ static struct nvmem_layout *nvmem_layout
 	if (!layout_np)
 		return NULL;
 
+	/*
+	 * In case the nvmem device was built-in while the layout was built as a
+	 * module, we shall manually request the layout driver loading otherwise
+	 * we'll never have any match.
+	 */
+	of_request_module(layout_np);
+
 	spin_lock(&nvmem_layout_lock);
 
 	list_for_each_entry(l, &nvmem_layouts, node) {
