linux-kernel - Re: [PATCH 2/9] clk: reparent orphans after critical clocks enabled

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Date:   Mon, 19 Jun 2017 18:51:40 -0700
From:   Stephen Boyd <sboyd@...eaurora.org>
To:     Dong Aisheng <aisheng.dong@....com>
Cc:     linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, mturquette@...libre.com,
        shawnguo@...nel.org, Anson.Huang@....com, ping.bai@....com
Subject: Re: [PATCH 2/9] clk: reparent orphans after critical clocks enabled

On 05/15, Dong Aisheng wrote:
> The orphan clocks reparent operation should be moved after the critical
> clocks enabled, otherwise it may get a chance to disable a newly registered
> critical clock which triggers the following warning.
> 
> [    0.000000] WARNING: CPU: 0 PID: 0 at drivers/clk/clk.c:597 clk_core_disable+0xb4/0xe0
> [    0.000000] Modules linked in:
> [    0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.11.0-rc1-00056-gdff1f66-dirty #1373
> [    0.000000] Hardware name: Generic DT based system
> [    0.000000] Backtrace:
> [    0.000000] [<c010c4bc>] (dump_backtrace) from [<c010c764>] (show_stack+0x18/0x1c)
> [    0.000000]  r6:600000d3 r5:00000000 r4:c0e26358 r3:00000000
> [    0.000000] [<c010c74c>] (show_stack) from [<c040599c>] (dump_stack+0xb4/0xe8)
> [    0.000000] [<c04058e8>] (dump_stack) from [<c0125c94>] (__warn+0xd8/0x104)
> [    0.000000]  r10:c0c21cd0 r9:c048aa78 r8:00000255 r7:00000009 r6:c0c1cd90 r5:00000000
> [    0.000000]  r4:00000000 r3:c0e01d34
> [    0.000000] [<c0125bbc>] (__warn) from [<c0125d74>] (warn_slowpath_null+0x28/0x30)
> [    0.000000]  r9:00000000 r8:ef00bf80 r7:c165ac4c r6:ef00bf80 r5:ef00bf80 r4:ef00bf80
> [    0.000000] [<c0125d4c>] (warn_slowpath_null) from [<c048aa78>] (clk_core_disable+0xb4/0xe0)
> [    0.000000] [<c048a9c4>] (clk_core_disable) from [<c048be88>] (clk_core_disable_lock+0x20/0x2c)
> [    0.000000]  r4:000000d3 r3:c0e0af00
> [    0.000000] [<c048be68>] (clk_core_disable_lock) from [<c048c224>] (clk_core_disable_unprepare+0x14/0x28)
> [    0.000000]  r5:00000000 r4:ef00bf80
> [    0.000000] [<c048c210>] (clk_core_disable_unprepare) from [<c048c270>] (__clk_set_parent_after+0x38/0x54)
> [    0.000000]  r4:ef00bd80 r3:000010a0
> [    0.000000] [<c048c238>] (__clk_set_parent_after) from [<c048daa8>] (clk_register+0x4d0/0x648)
> [    0.000000]  r6:ef00d500 r5:ef00bf80 r4:ef00bd80 r3:ef00bfd4
> [    0.000000] [<c048d5d8>] (clk_register) from [<c048dc30>] (clk_hw_register+0x10/0x1c)
> [    0.000000]  r9:00000000 r8:00000003 r7:00000000 r6:00000824 r5:00000001 r4:ef00d500
> [    0.000000] [<c048dc20>] (clk_hw_register) from [<c048e698>] (_register_divider+0xcc/0x120)
> [    0.000000] [<c048e5cc>] (_register_divider) from [<c048e730>] (clk_register_divider+0x44/0x54)
> [    0.000000]  r10:00000004 r9:00000003 r8:00000001 r7:00000000 r6:00000003 r5:00000001
> [    0.000000]  r4:f0810030
> [    0.000000] [<c048e6ec>] (clk_register_divider) from [<c0d3ff58>] (imx7ulp_clocks_init+0x558/0xe98)
> [    0.000000]  r7:c0e296f8 r6:c165c808 r5:00000000 r4:c165c808
> [    0.000000] [<c0d3fa00>] (imx7ulp_clocks_init) from [<c0d24db0>] (of_clk_init+0x118/0x1e0)
> [    0.000000]  r10:00000001 r9:c0e01f68 r8:00000000 r7:c0e01f60 r6:ef7f8974 r5:ef0035c0
> [    0.000000]  r4:00000006
> [    0.000000] [<c0d24c98>] (of_clk_init) from [<c0d04a50>] (time_init+0x2c/0x38)
> [    0.000000]  r10:efffed40 r9:c0d61a48 r8:c0e78000 r7:c0e07900 r6:ffffffff r5:c0e78000
> [    0.000000]  r4:00000000
> [    0.000000] [<c0d04a24>] (time_init) from [<c0d00b8c>] (start_kernel+0x218/0x394)
> [    0.000000] [<c0d00974>] (start_kernel) from [<6000807c>] (0x6000807c)
> [    0.000000]  r10:00000000 r9:410fc075 r8:6000406a r7:c0e0c930 r6:c0d61a44 r5:c0e07918
> [    0.000000]  r4:c0e78294
> [    0.000000] ---[ end trace 0000000000000000 ]---

The warning is long and scary and spans many lines, but the
scenario is described in one sentence. Please further describe
the scenario that introduces this warning without requiring the
reviewer to figure it out themselves! I certainly won't remember
2 years from now what happened here.

> 
> Cc: Stephen Boyd <sboyd@...eaurora.org>
> Cc: Michael Turquette <mturquette@...libre.com>
> Cc: Shawn Guo <shawnguo@...nel.org>
> Signed-off-by: Dong Aisheng <aisheng.dong@....com>

This would want a fixes tag assuming it's fixing something.

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