[PATCH] nvmem: include bit index in cell sysfs file name

[srinivas . kandagatla]

From: Arnd Bergmann <arnd@xxxxxxxx>

Creating sysfs files for all Cells caused a boot failure for linux-6.8-rc1 on
Apple M1, which (in downstream dts files) has multiple nvmem cells that use the
same byte address. This causes the device probe to fail with

[    0.605336] sysfs: cannot create duplicate filename '/devices/platform/soc@200000000/2922bc000.efuse/apple_efuses_nvmem0/cells/efuse@a10'
[    0.605347] CPU: 7 PID: 1 Comm: swapper/0 Tainted: G S                 6.8.0-rc1-arnd-5+ #133
[    0.605355] Hardware name: Apple Mac Studio (M1 Ultra, 2022) (DT)
[    0.605362] Call trace:
[    0.605365]  show_stack+0x18/0x2c
[    0.605374]  dump_stack_lvl+0x60/0x80
[    0.605383]  dump_stack+0x18/0x24
[    0.605388]  sysfs_warn_dup+0x64/0x80
[    0.605395]  sysfs_add_bin_file_mode_ns+0xb0/0xd4
[    0.605402]  internal_create_group+0x268/0x404
[    0.605409]  sysfs_create_groups+0x38/0x94
[    0.605415]  devm_device_add_groups+0x50/0x94
[    0.605572]  nvmem_populate_sysfs_cells+0x180/0x1b0
[    0.605682]  nvmem_register+0x38c/0x470
[    0.605789]  devm_nvmem_register+0x1c/0x6c
[    0.605895]  apple_efuses_probe+0xe4/0x120
[    0.606000]  platform_probe+0xa8/0xd0

As far as I can tell, this is a problem for any device with multiple cells on
different bits of the same address. Avoid the issue by changing the file name
to include the first bit number.

Fixes: 0331c611949f ("nvmem: core: Expose cells through sysfs")
Link: https://github.com/AsahiLinux/linux/blob/bd0a1a7d4/arch/arm64/boot/dts/apple/t600x-dieX.dtsi#L156
Cc: regressions@xxxxxxxxxxxxxxx
Cc: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>
Cc: Rafał Miłecki <rafal@xxxxxxxxxx>
Cc: Chen-Yu Tsai <wenst@xxxxxxxxxxxx>
Cc: Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: asahi@xxxxxxxxxxxxxxx
Cc: Sven Peter <sven@xxxxxxxxxxxxx>
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx>
---
Hi Greg, 

Here is a fix in nvmem for 6.8, could you queue these for next possible rc.

Did not cc Stable as this is only targeted for 6.8 and no backporting is
required.

Thanks,
Srini

 Documentation/ABI/testing/sysfs-nvmem-cells | 16 ++++++++--------
 drivers/nvmem/core.c                        |  5 +++--
 2 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-nvmem-cells b/Documentation/ABI/testing/sysfs-nvmem-cells
index 7af70adf3690..c7c9444f92a8 100644
--- a/Documentation/ABI/testing/sysfs-nvmem-cells
+++ b/Documentation/ABI/testing/sysfs-nvmem-cells
@@ -4,18 +4,18 @@ KernelVersion:	6.5
 Contact:	Miquel Raynal <miquel.raynal@xxxxxxxxxxx>
 Description:
 		The "cells" folder contains one file per cell exposed by the
-		NVMEM device. The name of the file is: <name>@<where>, with
-		<name> being the cell name and <where> its location in the NVMEM
-		device, in hexadecimal (without the '0x' prefix, to mimic device
-		tree node names). The length of the file is the size of the cell
-		(when known). The content of the file is the binary content of
-		the cell (may sometimes be ASCII, likely without trailing
-		character).
+		NVMEM device. The name of the file is: "<name>@<byte>,<bit>",
+		with <name> being the cell name and <where> its location in
+		the NVMEM device, in hexadecimal bytes and bits (without the
+		'0x' prefix, to mimic device tree node names). The length of
+		the file is the size of the cell (when known). The content of
+		the file is the binary content of the cell (may sometimes be
+		ASCII, likely without trailing character).
 		Note: This file is only present if CONFIG_NVMEM_SYSFS
 		is enabled.
 
 		Example::
 
-		  hexdump -C /sys/bus/nvmem/devices/1-00563/cells/product-name@d
+		  hexdump -C /sys/bus/nvmem/devices/1-00563/cells/product-name@d,0
 		  00000000  54 4e 34 38 4d 2d 50 2d  44 4e         |TN48M-P-DN|
 		  0000000a
diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index 980123fb4dde..eb357ac2e54a 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -460,8 +460,9 @@ static int nvmem_populate_sysfs_cells(struct nvmem_device *nvmem)
 	list_for_each_entry(entry, &nvmem->cells, node) {
 		sysfs_bin_attr_init(&attrs[i]);
 		attrs[i].attr.name = devm_kasprintf(&nvmem->dev, GFP_KERNEL,
-						    "%s@%x", entry->name,
-						    entry->offset);
+						    "%s@%x,%x", entry->name,
+						    entry->offset,
+						    entry->bit_offset);
 		attrs[i].attr.mode = 0444;
 		attrs[i].size = entry->bytes;
 		attrs[i].read = &nvmem_cell_attr_read;
-- 
2.25.1