linux-kernel - [PATCH v2 04/12] MIPS: pm-cps: Update comments on barrier instructions

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Date:   Wed, 7 Sep 2016 10:45:12 +0100
From:   Matt Redfearn <matt.redfearn@...tec.com>
To:     Ralf Baechle <ralf@...ux-mips.org>
CC:     <linux-mips@...ux-mips.org>,
        Matt Redfearn <matt.redfearn@...tec.com>,
        Adam Buchbinder <adam.buchbinder@...il.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Kees Cook <keescook@...omium.org>,
        <linux-kernel@...r.kernel.org>,
        Markos Chandras <markos.chandras@...tec.com>,
        Paul Burton <paul.burton@...tec.com>
Subject: [PATCH v2 04/12] MIPS: pm-cps: Update comments on barrier instructions

This code makes large use of barriers, which had quite vague
descriptions. Update the comments to make the choice of barrier and
reason for it more clear.

Signed-off-by: Matt Redfearn <matt.redfearn@...tec.com>
Reviewed-by: Paul Burton <paul.burton@...tec.com>

---

Changes in v2:
Update comments on barriers

 arch/mips/kernel/pm-cps.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/arch/mips/kernel/pm-cps.c b/arch/mips/kernel/pm-cps.c
index 2faa227a032e..7e8d4aa22233 100644
--- a/arch/mips/kernel/pm-cps.c
+++ b/arch/mips/kernel/pm-cps.c
@@ -315,7 +315,7 @@ static int __init cps_gen_flush_fsb(u32 **pp, struct uasm_label **pl,
 			     i * line_size * line_stride, t0);
 	}
 
-	/* Completion barrier */
+	/* Barrier ensuring previous cache invalidates are complete */
 	uasm_i_sync(pp, stype_memory);
 	uasm_i_ehb(pp);
 
@@ -414,7 +414,7 @@ static void * __init cps_gen_entry_code(unsigned cpu, enum cps_pm_state state)
 		uasm_il_beqz(&p, &r, t2, lbl_incready);
 		uasm_i_addiu(&p, t1, t1, 1);
 
-		/* Ordering barrier */
+		/* Barrier ensuring all CPUs see the updated r_nc_count value */
 		uasm_i_sync(&p, stype_ordering);
 
 		/*
@@ -467,7 +467,7 @@ static void * __init cps_gen_entry_code(unsigned cpu, enum cps_pm_state state)
 	cps_gen_cache_routine(&p, &l, &r, &cpu_data[cpu].dcache,
 			      Index_Writeback_Inv_D, lbl_flushdcache);
 
-	/* Completion barrier */
+	/* Barrier ensuring previous cache invalidates are complete */
 	uasm_i_sync(&p, stype_memory);
 	uasm_i_ehb(&p);
 
@@ -480,7 +480,7 @@ static void * __init cps_gen_entry_code(unsigned cpu, enum cps_pm_state state)
 	uasm_i_sw(&p, t0, 0, r_pcohctl);
 	uasm_i_lw(&p, t0, 0, r_pcohctl);
 
-	/* Sync to ensure previous interventions are complete */
+	/* Barrier to ensure write to coherence control is complete */
 	uasm_i_sync(&p, stype_intervention);
 	uasm_i_ehb(&p);
 
@@ -526,7 +526,7 @@ static void * __init cps_gen_entry_code(unsigned cpu, enum cps_pm_state state)
 			goto gen_done;
 		}
 
-		/* Completion barrier */
+		/* Barrier to ensure write to CPC command is complete */
 		uasm_i_sync(&p, stype_memory);
 		uasm_i_ehb(&p);
 	}
@@ -561,7 +561,7 @@ static void * __init cps_gen_entry_code(unsigned cpu, enum cps_pm_state state)
 	uasm_i_sw(&p, t0, 0, r_pcohctl);
 	uasm_i_lw(&p, t0, 0, r_pcohctl);
 
-	/* Completion barrier */
+	/* Barrier to ensure write to coherence control is complete */
 	uasm_i_sync(&p, stype_memory);
 	uasm_i_ehb(&p);
 
@@ -575,7 +575,7 @@ static void * __init cps_gen_entry_code(unsigned cpu, enum cps_pm_state state)
 		uasm_il_beqz(&p, &r, t2, lbl_decready);
 		uasm_i_andi(&p, v0, t1, (1 << fls(smp_num_siblings)) - 1);
 
-		/* Ordering barrier */
+		/* Barrier ensuring all CPUs see the updated r_nc_count value */
 		uasm_i_sync(&p, stype_ordering);
 	}
 
@@ -597,7 +597,7 @@ static void * __init cps_gen_entry_code(unsigned cpu, enum cps_pm_state state)
 		 */
 		uasm_build_label(&l, p, lbl_secondary_cont);
 
-		/* Ordering barrier */
+		/* Barrier ensuring all CPUs see the updated r_nc_count value */
 		uasm_i_sync(&p, stype_ordering);
 	}
 
-- 
2.7.4