From: Vineet Gupta <Vineet.Gupta1@synopsys.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"arnd@arndb.de" <arnd@arndb.de>,
"arc-linux-dev@synopsys.com" <arc-linux-dev@synopsys.com>
Subject: Re: [PATCH 20/28] ARCv2: barriers
Date: Wed, 10 Jun 2015 09:34:18 +0000 [thread overview]
Message-ID: <C2D7FE5348E1B147BCA15975FBA23075665A4FFE@IN01WEMBXB.internal.synopsys.com> (raw)
In-Reply-To: 20150609124008.GA3644@twins.programming.kicks-ass.net
On Tuesday 09 June 2015 06:10 PM, Peter Zijlstra wrote:
> On Tue, Jun 09, 2015 at 05:18:20PM +0530, Vineet Gupta wrote:
>
> A description of how your hardware works; or a reference to the platform
> documentation would not go amiss.
Honestly the docs group is working on a publicly sharable version of PRM
(Programmer's Reference Manual) but it might take some more time. I'm sure kernel
developers including you don't like to sign an NDA.... The information I have in
comments is pretty much what we have in there w.r.t. the barrier instructions. But
I will capture the the weak memory ordering and other details as part of changelog
here too.
>> [snip ....]
>> +/*
>> + * DMB:
>> + * - Ensures that selected memory operation issued before it will complete
>> + * before any subsequent memory operation of same type
>> + */
>> +#define smp_mb() asm volatile("dmb 3\n" : : : "memory")
>> +#define smp_rmb() asm volatile("dmb 1\n" : : : "memory")
>> +#define smp_wmb() asm volatile("dmb 2\n" : : : "memory")
>> +
>> +/*
>> + * DSYNC:
>> + * - Waits for completion of all outstanding memory operations before any new
>> + * operations can begin
>> + * - Includes implicit memory operations such as cache/TLB/BPU maintenance ops
>> + * - Lighter version of SYNC as it doesn't wait for non-memory operations
>> + */
>> +#define mb() asm volatile("dsync\n" : : : "memory")
> So mb() is supposed to order against things like DMA memory ops, is DMA
> part of point 1 or 3, if 3, this is not a suitable instruction.
Can u please explain the DMA case a bit more ? From what I understood and used in
say ethernet driver, it is more of a line drawn between say cpu updating a shared
buffer descriptor and kicking a MMIO register (which in turn could initiate a DMA)
but I'm not sure how mb() can possibly order with DMA per se (unless there's some
advanced form of IO-coherency)
-Vineet
>
>> +#else /* CONFIG_ISA_ARCOMPACT */
>> +
>> +/* SYNC:
>> + * - Waits for completion of all outstanding memory transactions AND all
>> + * previous instructions to reture
>> + */
>> +#define mb() asm volatile("sync\n" : : : "memory")
>> +
>> +#endif /* CONFIG_ISA_ARCV2 */
>
>
next prev parent reply other threads:[~2015-06-10 9:36 UTC|newest]
Thread overview: 109+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-09 11:48 [PATCH 00/28] ARCv2 port to Linux - (B) ISA / Core / platform support Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 01/28] ARCv2: [intc] HS38 core interrupt controller Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 02/28] ARCv2: Support for ARCv2 ISA and HS38x cores Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 03/28] ARCv2: STAR 9000793984: Handle return from intr to Delay Slot Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 04/28] ARCv2: STAR 9000808988: signals involving " Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 05/28] ARCv2: STAR 9000814690: Really Re-enable interrupts to avoid deadlocks Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 06/28] ARCv2: MMUv4: TLB programming Model changes Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 07/28] ARCv2: MMUv4: cache programming model changes Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 08/28] ARCv2: MMUv4: support aliasing icache config Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 09/28] ARCv2: optimised string/mem lib routines Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 10/28] ARCv2: Adhere to Zero Delay loop restriction Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 11/28] ARCv2: extable: Enable sorting at build time Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-24 5:51 ` Vineet Gupta
2015-06-24 5:51 ` Vineet Gupta
2015-06-29 20:38 ` David Daney
2015-06-30 4:41 ` Vineet Gupta
2015-06-30 4:41 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 12/28] ARCv2: clocksource: Introduce 64bit local RTC counter Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 13/28] ARC: make plat_smp_ops weak to allow over-rides Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 14/28] ARCv2: SMP: ARConnect debug/robustness Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 15/28] ARCv2: SMP: clocksource: Enable Global Real Time counter Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 16/28] ARCv2: SMP: intc: IDU 2nd level intc for dynamic IRQ distribution Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 17/28] ARC: add compiler barrier to LLSC based cmpxchg Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 12:23 ` Peter Zijlstra
2015-06-09 11:48 ` [PATCH 18/28] ARC: add smp barriers around atomics per memory-barrriers.txt Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 12:30 ` Peter Zijlstra
2015-06-10 9:17 ` Vineet Gupta
2015-06-10 10:53 ` Peter Zijlstra
2015-06-11 13:03 ` Vineet Gupta
2015-06-12 12:15 ` [PATCH v2] ARC: add smp barriers around atomics per Documentation/atomic_ops.txt Vineet Gupta
2015-06-12 12:15 ` Vineet Gupta
2015-06-12 13:04 ` Peter Zijlstra
2015-06-12 13:16 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 19/28] arch: conditionally define smp_{mb,rmb,wmb} Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 12:32 ` Peter Zijlstra
2015-06-09 11:48 ` [PATCH 20/28] ARCv2: barriers Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 12:40 ` Peter Zijlstra
2015-06-10 9:34 ` Vineet Gupta [this message]
2015-06-10 10:58 ` Peter Zijlstra
2015-06-10 13:01 ` Will Deacon
2015-06-11 12:13 ` Vineet Gupta
2015-06-11 13:39 ` Will Deacon
2015-06-19 13:13 ` Vineet Gupta
2015-06-19 13:13 ` Vineet Gupta
2015-06-19 13:13 ` Vineet Gupta
2015-06-22 13:36 ` Will Deacon
2015-06-22 13:36 ` Will Deacon
2015-06-22 13:36 ` Will Deacon
2015-06-23 7:58 ` [PATCH v2 " Vineet Gupta
2015-06-23 7:58 ` Vineet Gupta
2015-06-23 8:49 ` Will Deacon
2015-06-23 9:03 ` Vineet Gupta
2015-06-23 9:26 ` Will Deacon
2015-06-23 9:52 ` [PATCH v3 22/28] " Vineet Gupta
2015-06-23 9:52 ` Vineet Gupta
2015-06-23 16:28 ` Will Deacon
2015-06-23 9:25 ` [PATCH v2 20/28] " Peter Zijlstra
2015-06-23 8:02 ` [PATCH " Vineet Gupta
2015-06-09 11:48 ` [PATCH 21/28] ARC: Reduce bitops lines of code using macros Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-12 12:20 ` [PATCH v2] " Vineet Gupta
2015-06-12 12:20 ` Vineet Gupta
2015-06-12 13:05 ` Peter Zijlstra
2015-06-09 11:48 ` [PATCH 22/28] ARCv2: STAR 9000837815 workaround hardware exclusive transactions livelock Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 12:35 ` Peter Zijlstra
2015-06-10 10:01 ` Vineet Gupta
2015-06-10 11:02 ` Peter Zijlstra
2015-06-19 9:55 ` [PATCH v2 " Vineet Gupta
2015-06-19 9:55 ` Vineet Gupta
2015-06-19 9:59 ` Will Deacon
2015-06-19 10:09 ` Vineet Gupta
2015-06-23 7:59 ` Vineet Gupta
2015-06-23 7:59 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 23/28] ARCv2: SLC: Handle explcit flush for DMA ops (w/o IO-coherency) Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 24/28] ARCv2: All bits in place, allow ARCv2 builds Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 25/28] ARCv2: [nsim*hs*] Support simulation platforms for HS38x cores Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 26/28] ARC: [axs101] Prepare for AXS103 Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 27/28] ARCv2: [axs103] Support ARC SDP FPGA platform for HS38x cores Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 28/28] ARCv2: [vdk] dts files and defconfig for HS38 VDK Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
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