linux-kernel - Re: [PATCH 4/4] x86/mce/AMD: Add comments for easier understanding

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Date:	Tue, 23 Feb 2016 13:35:30 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Aravind Gopalakrishnan <Aravind.Gopalakrishnan@....com>
Cc:	tony.luck@...el.com, hpa@...or.com, mingo@...hat.com,
	tglx@...utronix.de, dougthompson@...ssion.com,
	mchehab@....samsung.com, x86@...nel.org,
	linux-edac@...r.kernel.org, linux-kernel@...r.kernel.org,
	ashok.raj@...el.com, gong.chen@...ux.intel.com,
	len.brown@...el.com, peterz@...radead.org, ak@...ux.intel.com,
	alexander.shishkin@...ux.intel.com
Subject: Re: [PATCH 4/4] x86/mce/AMD: Add comments for easier understanding

On Tue, Feb 16, 2016 at 03:45:11PM -0600, Aravind Gopalakrishnan wrote:
> In an attempt to help folks not very familiar with the code to
> understand what the code is doing, adding a bit of helper
> comments around some more important functions in the driver
> to describe them.
> 
> No functional change is introduced.
> 
> Signed-off-by: Aravind Gopalakrishnan <Aravind.Gopalakrishnan@....com>
> ---
>  arch/x86/kernel/cpu/mcheck/mce_amd.c | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
> 
> diff --git a/arch/x86/kernel/cpu/mcheck/mce_amd.c b/arch/x86/kernel/cpu/mcheck/mce_amd.c
> index 4bdc836..d2b6001 100644
> --- a/arch/x86/kernel/cpu/mcheck/mce_amd.c
> +++ b/arch/x86/kernel/cpu/mcheck/mce_amd.c
> @@ -184,6 +184,11 @@ static int lvt_off_valid(struct threshold_block *b, int apic, u32 lo, u32 hi)
>  };
>  
>  /*
> + * Set the error_count and interrupt_enable sysfs attributes here.
> + * This function gets called during the init phase and when someone
> + * makes changes to either of the sysfs attributes.
> + * During init phase, we also program Interrupt type as 'APIC' and
> + * verify if LVT offset obtained from MCx_MISC is valid.
>   * Called via smp_call_function_single(), must be called with correct
>   * cpu affinity.
>   */

I don't think that's what threshold_restart_bank() does...

Also, that comment is too much - it shouldn't explain "what" but "why".

> @@ -262,6 +267,11 @@ static int setup_APIC_deferred_error(int reserved, int new)
>  	return reserved;
>  }
>  
> +/*
> + * Obtain LVT offset from MSR_CU_DEF_ERR and call
> + * setup_APIC_deferred_error() to program relevant APIC register.
> + * Also, register a deferred error interrupt handler
> + */

No, that's basically spelling what the code does.

>  static void deferred_error_interrupt_enable(struct cpuinfo_x86 *c)
>  {
>  	u32 low = 0, high = 0;
> @@ -338,6 +348,14 @@ nextaddr_out:
>  		return addr;
>  }
>  
> +/*
> + * struct threshold_block descriptor tracks useful info regarding the
> + * banks' MISC register. Among other things, it tracks whether interrupt
> + * is possible for the given bank, the threshold limit and the sysfs object
> + * that outputs these info.

That should be in form of comments explaining what the members of struct
threshold_block are, where that struct is defined.

> Initializing the struct here, programming
> + * LVT offset for threshold interrupts and registering a interrupt handler
> + * if we haven't already done so

Also spelling the code.

> + */
>  static int
>  prepare_threshold_block(unsigned int bank, unsigned int block, u32 addr,
>  			int offset, u32 misc_high)
-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.