Sagar Kamble 49a6676ef6 gpu: nvgpu: remove unnecessary devfreq limit checks ...

gk20a_scale_target is called through the target member of a
devfreq_profile. It is only called from devfreqs update_devfreq
function or through governor_passive. governor_passive is not used for
nvgpu.

Since update_devfreq already enforce the devfreq limits,
gka20_scale_target can be simplified by only checking pm_qos
limits and also only if GK20A_PM_QOS is enabled.

This also resolves a race between creating devfreq sysfs
files and setting 'l->devfreq' in gk20a_scale_init that can
lead to accessing a NULL pointer by writing to the sysfs files.

Example:
Unable to handle kernel NULL pointer dereference at virtual address 00000430
<snip>
Call trace:
[<000000006aa50d89>] gk20a_scale_target+0x5c/0x120 [nvgpu]
[<00000000e5a63f7c>] update_devfreq+0xec/0x22c
[<0000000014a13c8a>] max_freq_store+0xa8/0xfc
[<0000000072139393>] dev_attr_store+0x48/0x60
[<000000008ec280df>] sysfs_kf_write+0x60/0x70
[<0000000038427ed5>] kernfs_fop_write+0xc4/0x1e0
[<00000000c0b74aa9>] __vfs_write+0x60/0x14c
[<0000000078fcebb4>] vfs_write+0xb0/0x1b4
[<000000007720da30>] SyS_write+0x74/0xf0
[<0000000067443e2c>] __sys_trace_return+0x0/0x4

Bug 3910155

Change-Id: I7193cc5ea85454acf0890b3ca8d1c3526ca8517e
Signed-off-by: Ken Chang <kenc@nvidia.com>
Signed-off-by: Sagar Kamble <skamble@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/c/linux-nvgpu/+/2828219
Reviewed-by: Rajesh Devaraj <rdevaraj@nvidia.com>
Reviewed-by: Vijayakumar Subbu <vsubbu@nvidia.com>

2023-02-06 10:24:37 -08:00

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