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From: Serge Semin <Sergey.Semin@baikalelectronics.ru>
To: Vinod Koul <vkoul@kernel.org>
Cc: Serge Semin <fancer.lancer@gmail.com>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Viresh Kumar <vireshk@kernel.org>,
	Dan Williams <dan.j.williams@intel.com>,
	Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>,
	Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	Paul Burton <paulburton@kernel.org>,
	Ralf Baechle <ralf@linux-mips.org>, Arnd Bergmann <arnd@arndb.de>,
	Rob Herring <robh+dt@kernel.org>, <linux-mips@vger.kernel.org>,
	<devicetree@vger.kernel.org>, <dmaengine@vger.kernel.org>,
	<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 5/6] dmaengine: dw: Introduce max burst length hw config
Date: Thu, 21 May 2020 04:47:05 +0300
Message-ID: <20200521014705.ha7mpxoio4gitjox@mobilestation> (raw)
In-Reply-To: <20200519170714.GT374218@vkoul-mobl.Dlink>

On Tue, May 19, 2020 at 10:37:14PM +0530, Vinod Koul wrote:
> On 17-05-20, 22:38, Serge Semin wrote:
> > On Fri, May 15, 2020 at 12:09:50PM +0530, Vinod Koul wrote:
> > > On 12-05-20, 22:12, Andy Shevchenko wrote:
> > > > On Tue, May 12, 2020 at 05:08:20PM +0300, Serge Semin wrote:
> > > > > On Fri, May 08, 2020 at 02:41:53PM +0300, Andy Shevchenko wrote:
> > > > > > On Fri, May 08, 2020 at 01:53:03PM +0300, Serge Semin wrote:

[nip]

> > > > > > But let's see what we can do better. Since maximum is defined on the slave side
> > > > > > device, it probably needs to define minimum as well, otherwise it's possible
> > > > > > that some hardware can't cope underrun bursts.
> > > > > 
> > > > > There is no need to define minimum if such limit doesn't exists except a
> > > > > natural 1. Moreover it doesn't exist for all DMA controllers seeing noone has
> > > > > added such capability into the generic DMA subsystem so far.
> > > > 
> > > > There is a contract between provider and consumer about DMA resource. That's
> > > > why both sides should participate in fulfilling it. Theoretically it may be a
> > > > hardware that doesn't support minimum burst available in DMA by a reason. For
> > > > such we would need minimum to be provided as well.
> > > 
> > > Agreed and if required caps should be extended to tell consumer the
> > > minimum values supported.
> > 
> > Sorry, it's not required by our hardware. Is there any, which actually has such
> > limitation? (minimum burst length)
> 
> IIUC the idea is that you will tell maximum and minimum values supported
> and client can pick the best value. Esp in case of slave transfers
> things like burst, msize are governed by client capability and usage. So
> exposing the set to pick from would make sense

Agreed. I'll add min_burst capability.

-Sergey

> 
> -- 
> ~Vinod

  reply index

Thread overview: 72+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-06 13:10 [PATCH 0/5] dmaengine: dw: Take Baikal-T1 SoC DW DMAC peculiarities into account Sergey.Semin
2020-03-06 13:29 ` Andy Shevchenko
2020-03-06 13:30   ` Andy Shevchenko
2020-03-06 13:43     ` Vinod Koul
     [not found]     ` <20200306135050.40094803087C@mail.baikalelectronics.ru>
2020-03-09 21:45       ` Sergey Semin
     [not found]   ` <20200306133756.0F74C8030793@mail.baikalelectronics.ru>
2020-03-06 13:47     ` Sergey Semin
2020-03-06 14:11       ` Andy Shevchenko
     [not found]       ` <20200306141135.9C4F380307C2@mail.baikalelectronics.ru>
2020-03-09 22:08         ` Sergey Semin
2020-05-08 10:52 ` [PATCH v2 0/6] " Serge Semin
2020-05-08 10:52   ` [PATCH v2 1/6] dt-bindings: dma: dw: Convert DW DMAC to DT binding Serge Semin
2020-05-18 17:50     ` Rob Herring
2020-05-08 10:53   ` [PATCH v2 2/6] dt-bindings: dma: dw: Add max burst transaction length property Serge Semin
2020-05-08 11:12     ` Andy Shevchenko
2020-05-11 20:05       ` Serge Semin
2020-05-11 21:01         ` Andy Shevchenko
2020-05-11 21:35           ` Serge Semin
2020-05-12  9:08             ` Andy Shevchenko
2020-05-12 11:49               ` Serge Semin
2020-05-12 12:38                 ` Andy Shevchenko
2020-05-15  6:09                   ` Vinod Koul
2020-05-15 10:51                     ` Andy Shevchenko
2020-05-15 10:56                       ` Vinod Koul
2020-05-15 11:11                         ` Serge Semin
2020-05-17 17:47                           ` Serge Semin
2020-05-18 17:30                             ` Rob Herring
2020-05-18 19:30                               ` Serge Semin
2020-05-19 17:13                             ` Vinod Koul
2020-05-21  1:33                               ` Serge Semin
2020-05-08 10:53   ` [PATCH v2 3/6] dmaengine: dw: Set DMA device max segment size parameter Serge Semin
2020-05-08 11:21     ` Andy Shevchenko
2020-05-08 18:49       ` Vineet Gupta
2020-05-11 21:16       ` Serge Semin
2020-05-12 12:35         ` Andy Shevchenko
2020-05-12 17:01           ` Serge Semin
2020-05-15  6:16           ` Vinod Koul
2020-05-15 10:53             ` Andy Shevchenko
2020-05-17 18:22               ` Serge Semin
2020-05-08 10:53   ` [PATCH v2 4/6] dmaengine: dw: Print warning if multi-block is unsupported Serge Semin
2020-05-08 11:26     ` Andy Shevchenko
2020-05-08 11:53       ` Mark Brown
2020-05-08 19:06         ` Andy Shevchenko
2020-05-11  3:13           ` Serge Semin
2020-05-11 14:03             ` Andy Shevchenko
2020-05-11  2:10         ` Serge Semin
2020-05-11 11:58           ` Mark Brown
2020-05-11 13:45             ` Serge Semin
2020-05-11 13:58               ` Andy Shevchenko
2020-05-11 17:48                 ` Mark Brown
2020-05-11 18:25                   ` Serge Semin
2020-05-11 19:32                 ` Serge Semin
2020-05-11 21:07                   ` Andy Shevchenko
2020-05-11 21:08                     ` Andy Shevchenko
2020-05-12 12:42                       ` Serge Semin
2020-05-15  6:30                         ` Vinod Koul
2020-05-17 19:23                           ` Serge Semin
2020-05-19 17:02                             ` Vinod Koul
2020-05-21  1:40                               ` Serge Semin
2020-05-11 17:44               ` Mark Brown
2020-05-11 18:32                 ` Serge Semin
2020-05-11 21:32                   ` Mark Brown
2020-05-08 10:53   ` [PATCH v2 5/6] dmaengine: dw: Introduce max burst length hw config Serge Semin
2020-05-08 11:41     ` Andy Shevchenko
2020-05-12 14:08       ` Serge Semin
2020-05-12 19:12         ` Andy Shevchenko
2020-05-12 19:47           ` Serge Semin
2020-05-15 11:02             ` Andy Shevchenko
2020-05-15  6:39           ` Vinod Koul
2020-05-17 19:38             ` Serge Semin
2020-05-19 17:07               ` Vinod Koul
2020-05-21  1:47                 ` Serge Semin [this message]
2020-05-08 10:53   ` [PATCH v2 6/6] dmaengine: dw: Take HC_LLP flag into account for noLLP auto-config Serge Semin
2020-05-08 11:43     ` Andy Shevchenko

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