kernel: fix mtd/NVMEM regression affecting U-Boot env NVMEM driver

Fixes: 20736013e910 ("kernel: backport nvmem v6.6 fixes and v6.7 changes")
Fixes: https://github.com/openwrt/openwrt/issues/13831
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
(cherry picked from commit c997634c017294cb38cf6f9a0112860c7e736a53)

1 files changed, 48 insertions, 0 deletions

diff --git a/target/linux/generic/pending-5.15/401-mtd-don-t-register-NVMEM-devices-for-partitions-with.patch b/target/linux/generic/pending-5.15/401-mtd-don-t-register-NVMEM-devices-for-partitions-with.patch
new file mode 100644
index 0000000000..650e10a3a5
--- /dev/null
+++ b/target/linux/generic/pending-5.15/401-mtd-don-t-register-NVMEM-devices-for-partitions-with.patch
@@ -0,0 +1,48 @@
+From: =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= <rafal@milecki.pl>
+Date: Tue, 31 Oct 2023 15:51:01 +0100
+Subject: [PATCH] mtd: don't register NVMEM devices for partitions with custom
+ drivers
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+This fixes issue exposed by upstream commit f4cf4e5db331 ("Revert
+"nvmem: add new config option"").
+
+Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
+---
+ drivers/mtd/mtdcore.c | 23 +++++++++++++++++++++++
+ 1 file changed, 23 insertions(+)
+
+--- a/drivers/mtd/mtdcore.c
++++ b/drivers/mtd/mtdcore.c
+@@ -537,6 +537,29 @@ static int mtd_nvmem_add(struct mtd_info
+ 	struct device_node *node = mtd_get_of_node(mtd);
+ 	struct nvmem_config config = {};
+ 
++	/*
++	 * Do NOT register NVMEM device for any partition that is meant to be
++	 * handled by a U-Boot env driver. That would result in associating two
++	 * different NVMEM devices with the same OF node.
++	 *
++	 * An example of unwanted behaviour of above (forwardtrace):
++	 * of_get_mac_addr_nvmem()
++	 * of_nvmem_cell_get()
++	 * __nvmem_device_get()
++	 *
++	 * We can't have __nvmem_device_get() return "mtdX" NVMEM device instead
++	 * of U-Boot env NVMEM device. That would result in failing to find
++	 * NVMEM cell.
++	 *
++	 * This issue seems to affect U-Boot env case only and will go away with
++	 * switch to NVMEM layouts.
++	 */
++	if (of_device_is_compatible(node, "u-boot,env") ||
++	    of_device_is_compatible(node, "u-boot,env-redundant-bool") ||
++	    of_device_is_compatible(node, "u-boot,env-redundant-count") ||
++	    of_device_is_compatible(node, "brcm,env"))
++		return 0;
++
+ 	config.id = -1;
+ 	config.dev = &mtd->dev;
+ 	config.name = dev_name(&mtd->dev);