Re: [PATCH AUTOSEL 5.4 095/108] ARM: shmobile: Enable ARM_GLOBAL_TIMER on Cortex-A9 MPCore SoCs

Sasha Levin
2020-04-17T17:18:08Z

On Sun, Apr 12, 2020 at 10:44:01AM +0200, Geert Uytterhoeven wrote:
>Hi Sasha,
>
>On Sun, Apr 12, 2020 at 1:11 AM Sasha Levin <sashal@kernel.org> wrote:
>> From: Geert Uytterhoeven <geert+renesas@glider.be>
>>
>> [ Upstream commit 408324a3c5383716939eea8096a0f999a0665f7e ]
>>
>> SH-Mobile AG5 and R-Car H1 SoCs are based on the Cortex-A9 MPCore, which
>> includes a global timer.
>>
>> Enable the ARM global timer on these SoCs, which will be used for:
>> - the scheduler clock, improving scheduler accuracy from 10 ms to 3 or
>> 4 ns,
>> - delay loops, allowing removal of calls to shmobile_init_delay() from
>> the corresponding machine vectors.
>>
>> Note that when using an old DTB lacking the global timer, the kernel
>> will still work. However, loops-per-jiffies will no longer be preset,
>> and the delay loop will need to be calibrated during boot.
>
>I.e. to avoid this delay, this patch is best backported after backporting
>8443ffd1bbd5be74 ("ARM: dts: r8a7779: Add device node for ARM global timer"),
>df1a0aac0a533e6f ("ARM: dts: sh73a0: Add device node for ARM global timer").
>
>While the former has been backported to v5.[45]-stable, the latter hasn't,
>probably because it depends on
>61b58e3f6e518c51 ("ARM: dts: sh73a0: Rename twd clock to periph clock")
>
>So please backport the last two commits first.

Done, thanks!

--
Thanks,
Sasha