linux-kernel - Re: [PATCH] nvmem: include bit index in cell sysfs file name

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Message-ID: <20240124182256.776c164b@xps-13>
Date: Wed, 24 Jan 2024 18:22:56 +0100
From: Miquel Raynal <miquel.raynal@...tlin.com>
To: Arnd Bergmann <arnd@...nel.org>
Cc: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>, Arnd Bergmann
 <arnd@...db.de>, regressions@...ts.linux.dev, Rafał Miłecki <rafal@...ecki.pl>, Chen-Yu Tsai <wenst@...omium.org>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, asahi@...ts.linux.dev,
 Sven Peter <sven@...npeter.dev>, Michael Walle <michael@...le.cc>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] nvmem: include bit index in cell sysfs file name

Hi Arnd,

arnd@...nel.org wrote on Mon, 22 Jan 2024 16:34:10 +0100:

> From: Arnd Bergmann <arnd@...db.de>
> 
> 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

o_O	I didn't even know this was allowed...

> [    0.605336] sysfs: cannot create duplicate filename '/devices/platform/soc@...000000/2922bc000.efuse/apple_efuses_nvmem0/cells/efuse@...'
> [    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.

There is only one bit number right? We are talking about byte offsets
so this value can only range from 0 to 7? If we understand each other
correctly then why not, I'm fine with the extra ",0" thing.

> Fixes: 0088cbc19276 ("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@...ts.linux.dev
> Cc: Miquel Raynal <miquel.raynal@...tlin.com>
> Cc: Rafał Miłecki <rafal@...ecki.pl>
> Cc: Chen-Yu Tsai <wenst@...omium.org>
> Cc: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: asahi@...ts.linux.dev
> Cc: Sven Peter <sven@...npeter.dev>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---

Thanks,
Miquèl