linux-kernel - Re: [PATCH] x86, suspend: Save/restore THERM

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Date:	Tue, 18 Aug 2015 10:02:38 +0800
From:	Yu Chen <yu.c.chen@...el.com>
To:	Ingo Molnar <mingo@...nel.org>
CC:	rjw@...ysocki.net, pavel@....cz, tglx@...utronix.de,
	mingo@...hat.com, hpa@...or.com, rui.zhang@...el.com,
	x86@...nel.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86, suspend: Save/restore THERM_CONTROL register for
 suspend

（not sure if previous reply has been sent out)
Hi, Ingo, thanks for your review,
On 08/17/2015 06:11 PM, Ingo Molnar wrote:
>
> * Chen Yu <yu.c.chen@...el.com> wrote:
>
>
> So what your changelog fails to mention:
>
>   - You only add this code to the 64-bit kernel. Are 32-bit kernels not affected?
>
I missed the 32-bit case, I'll adjust them to 32/64-bit common path.
>   - the MSR read is done unconditionally. Is MSR_IA32_THERM_CONTROL available
>     architecturally and readable (and has sensible values) on all 64-bit capable
>     x86 CPUs that run this code path?
>
MSR_IA32_THERM_CONTROL is avaliable on Intel Pentium 4, Xeon, Pentium M
and later processors, so I think not all of the 32/64-bit x86 CPUs have
this regiser. Maybe codes like this would be more reasonable?
save:
ctx->clock_modulation_saved = !rdmsrl_safe(MSR_IA32_THERM_CONTROL,
	&ctxt->clock_modulation);
retore:
if (ctxt->clock_modulation_saved)
	wrmsrl(MSR_IA32_THERM_CONTROL, ctxt->clock_modulation);


Best Regards,
Yu
> Thanks,
>
> 	Ingo
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