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Commit 09074950 authored by Vineet Gupta's avatar Vineet Gupta
Browse files

ARC: add/fix some comments in code - no functional change 



Signed-off-by: default avatarVineet Gupta <vgupta@synopsys.com>
parent 6de6066c

arch/arc/boot/dts/axc003.dtsi

+7 −6
Original line number Diff line number Diff line
@@ -72,12 +72,13 @@ 
	};



	/*

	 * This INTC is actually connected to DW APB GPIO

	 * which acts as a wire between MB INTC and CPU INTC.

	 * GPIO INTC is configured in platform init code

	 * and here we mimic direct connection from MB INTC to

	 * CPU INTC, thus we set "interrupts = <7>" instead of

	 * "interrupts = <12>"

	 * The DW APB ICTL intc on MB is connected to CPU intc via a

	 * DT "invisible" DW APB GPIO block, configured to simply pass thru

	 * interrupts - setup accordinly in platform init (plat-axs10x/ax10x.c)

	 *

	 * So here we mimic a direct connection betwen them, ignoring the

	 * ABPG GPIO. Thus set "interrupts = <24>" (DW APB GPIO to core)

	 * instead of "interrupts = <12>" (DW APB ICTL to DW APB GPIO)

	 *

	 * This intc actually resides on MB, but we move it here to

	 * avoid duplicating the MB dtsi file given that IRQ from

arch/arc/include/asm/cmpxchg.h

+11 −11
Original line number Diff line number Diff line
@@ -110,18 +110,18 @@ static inline unsigned long __xchg(unsigned long val, volatile void *ptr, 
						 sizeof(*(ptr))))



/*

 * On ARC700, EX insn is inherently atomic, so by default "vanilla" xchg() need

 * not require any locking. However there's a quirk.

 * ARC lacks native CMPXCHG, thus emulated (see above), using external locking -

 * incidently it "reuses" the same atomic_ops_lock used by atomic APIs.

 * Now, llist code uses cmpxchg() and xchg() on same data, so xchg() needs to

 * abide by same serializing rules, thus ends up using atomic_ops_lock as well.

 * xchg() maps directly to ARC EX instruction which guarantees atomicity.

 * However in !LLSC config, it also needs to be use @atomic_ops_lock spinlock

 * due to a subtle reason:

 *  - For !LLSC, cmpxchg() needs to use that lock (see above) and there is lot

 *    of  kernel code which calls xchg()/cmpxchg() on same data (see llist.h)

 *    Hence xchg() needs to follow same locking rules.

 *

 * This however is only relevant if SMP and/or ARC lacks LLSC

 *   if (UP or LLSC)

 *      xchg doesn't need serialization

 *   else <==> !(UP or LLSC) <==> (!UP and !LLSC) <==> (SMP and !LLSC)

 *      xchg needs serialization

 * Technically the lock is also needed for UP (boils down to irq save/restore)

 * but we can cheat a bit since cmpxchg() atomic_ops_lock() would cause irqs to

 * be disabled thus can't possibly be interrpted/preempted/clobbered by xchg()

 * Other way around, xchg is one instruction anyways, so can't be interrupted

 * as such

 */



#if !defined(CONFIG_ARC_HAS_LLSC) && defined(CONFIG_SMP)

arch/arc/include/asm/perf_event.h

+1 −1
Original line number Diff line number Diff line
@@ -95,7 +95,7 @@ static const char * const arc_pmu_ev_hw_map[] = { 


	/* counts condition */

	[PERF_COUNT_HW_INSTRUCTIONS] = "iall",

	[PERF_COUNT_HW_BRANCH_INSTRUCTIONS] = "ijmp",

	[PERF_COUNT_HW_BRANCH_INSTRUCTIONS] = "ijmp", /* Excludes ZOL jumps */

	[PERF_COUNT_ARC_BPOK]         = "bpok",	  /* NP-NT, PT-T, PNT-NT */

	[PERF_COUNT_HW_BRANCH_MISSES] = "bpfail", /* NP-T, PT-NT, PNT-T */

arch/arc/kernel/perf_event.c

+2 −2
Original line number Diff line number Diff line
@@ -199,8 +199,8 @@ static void arc_pmu_start(struct perf_event *event, int flags) 
	event->hw.state = 0;



	/* enable ARC pmu here */

	write_aux_reg(ARC_REG_PCT_INDEX, idx);

	write_aux_reg(ARC_REG_PCT_CONFIG, hwc->config);

	write_aux_reg(ARC_REG_PCT_INDEX, idx);		/* counter # */

	write_aux_reg(ARC_REG_PCT_CONFIG, hwc->config);	/* condition */

}



static void arc_pmu_stop(struct perf_event *event, int flags)

arch/arc/kernel/process.c

+1 −1
Original line number Diff line number Diff line
@@ -65,7 +65,7 @@ asmlinkage void ret_from_fork(void); 
 * ------------------

 * |     r25        |   <==== top of Stack (thread.ksp)

 * ~                ~

 * |    --to--      |   (CALLEE Regs of user mode)

 * |    --to--      |   (CALLEE Regs of kernel mode)

 * |     r13        |

 * ------------------

 * |     fp         |