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

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Date:	Tue, 16 Feb 2016 15:45:11 -0600
From:	Aravind Gopalakrishnan <Aravind.Gopalakrishnan@....com>
To:	<bp@...en8.de>, <tony.luck@...el.com>, <hpa@...or.com>,
	<mingo@...hat.com>, <tglx@...utronix.de>,
	<dougthompson@...ssion.com>, <mchehab@....samsung.com>
CC:	<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: [PATCH 4/4] x86/mce/AMD: Add comments for easier understanding

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.
  */
@@ -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
+ */
 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. Initializing the struct here, programming
+ * LVT offset for threshold interrupts and registering a interrupt handler
+ * if we haven't already done so
+ */
 static int
 prepare_threshold_block(unsigned int bank, unsigned int block, u32 addr,
 			int offset, u32 misc_high)
@@ -673,6 +691,9 @@ static struct kobj_type threshold_ktype = {
 	.default_attrs		= default_attrs,
 };
 
+/*
+ * Initializing sysfs entries for each block within the MCA bank
+ */
 static int allocate_threshold_blocks(unsigned int cpu, unsigned int bank,
 				     unsigned int block, u32 address)
 {
-- 
2.7.0