From: Andy Shevchenko <andy.shevchenko@gmail.com>
To: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Serge Semin <fancer.lancer@gmail.com>,
Vinod Koul <vkoul@kernel.org>, Viresh Kumar <vireshk@kernel.org>,
Dan Williams <dan.j.williams@intel.com>,
Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>,
Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
Arnd Bergmann <arnd@arndb.de>, Rob Herring <robh+dt@kernel.org>,
linux-mips@vger.kernel.org,
devicetree <devicetree@vger.kernel.org>,
dmaengine <dmaengine@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 10/10] dmaengine: dw: Initialize max_sg_nents with nollp flag
Date: Thu, 28 May 2020 23:31:09 +0300 [thread overview]
Message-ID: <CAHp75Vd0ujdxzXtE3-XGxrbJHBJqj6suBvN4VUQbApPSNCstmg@mail.gmail.com> (raw)
In-Reply-To: <20200528155017.ayetroojyvxl74kb@mobilestation>
On Thu, May 28, 2020 at 6:52 PM Serge Semin
<Sergey.Semin@baikalelectronics.ru> wrote:
> On Thu, May 28, 2020 at 05:56:30PM +0300, Andy Shevchenko wrote:
> > On Wed, May 27, 2020 at 01:50:21AM +0300, Serge Semin wrote:
...
> > In principal I agree, one nit below.
> > If you are okay with it, feel free to add my Rb tag.
> > > + /*
> > > + * It might be crucial for some devices to have the hardware
> > > + * accelerated multi-block transfers supported, aka LLPs in DW DMAC
> > > + * notation. So if LLPs are supported then max_sg_nents is set to
> > > + * zero which means unlimited number of SG entries can be handled in a
> > > + * single DMA transaction, otherwise it's just one SG entry.
> > > + */
> >
> > > + caps->max_sg_nents = dwc->nollp;
> >
>
> > To be on the safer side I would explicitly do it like
> >
> > if (dwc->nollp)
> > /* your nice comment */
> > = 1;
> > else
> > /* Unlimited */
> > = 0;
> >
> > type or content of nollp theoretically can be changed and this will affect maximum segments.
>
> Agree. Though I don't like formatting you suggested. If I add my nice comment
> between if-statement and assignment the the former will be look detached from
> the if-statement, which seems a bit ugly. So I'd leave the comment above the
> whole if-else statement, especially seeing I've already mentioned there about
> the unlimited number of SG entries there.
>
> /*
> * It might be crucial for some devices to have the hardware
> * accelerated multi-block transfers supported, aka LLPs in DW DMAC
> * notation. So if LLPs are supported then max_sg_nents is set to
> * zero which means unlimited number of SG entries can be handled in a
> * single DMA transaction, otherwise it's just one SG entry.
> */
> if (dwc->nollp)
> caps->max_sg_nents = 1;
> else
> caps->max_sg_nents = 0;
Fine with me, thanks!
--
With Best Regards,
Andy Shevchenko
prev parent reply other threads:[~2020-05-28 20:31 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-26 22:50 [PATCH v3 00/10] dmaengine: dw: Take Baikal-T1 SoC DW DMAC peculiarities into account Serge Semin
2020-05-26 22:50 ` [PATCH v3 01/10] dt-bindings: dma: dw: Convert DW DMAC to DT binding Serge Semin
2020-05-26 22:50 ` [PATCH v3 02/10] dt-bindings: dma: dw: Add max burst transaction length property Serge Semin
2020-05-26 22:50 ` [PATCH v3 03/10] dmaengine: Introduce min burst length capability Serge Semin
2020-05-28 14:21 ` Andy Shevchenko
2020-05-26 22:50 ` [PATCH v3 04/10] dmaengine: Introduce max SG list entries capability Serge Semin
2020-05-28 14:22 ` Andy Shevchenko
2020-05-26 22:50 ` [PATCH v3 05/10] dmaengine: Introduce DMA-device device_caps callback Serge Semin
2020-05-28 14:42 ` Andy Shevchenko
2020-05-28 15:19 ` Serge Semin
2020-05-28 20:34 ` Andy Shevchenko
2020-05-26 22:50 ` [PATCH v3 06/10] dmaengine: dw: Take HC_LLP flag into account for noLLP auto-config Serge Semin
2020-05-26 22:50 ` [PATCH v3 07/10] dmaengine: dw: Set DMA device max segment size parameter Serge Semin
2020-05-26 22:50 ` [PATCH v3 08/10] dmaengine: dw: Add dummy device_caps callback Serge Semin
2020-05-28 14:53 ` Andy Shevchenko
2020-05-28 15:27 ` Serge Semin
2020-05-28 20:29 ` Andy Shevchenko
2020-05-28 20:34 ` Serge Semin
2020-05-26 22:50 ` [PATCH v3 09/10] dmaengine: dw: Introduce max burst length hw config Serge Semin
2020-05-28 14:52 ` Andy Shevchenko
2020-05-28 15:40 ` Serge Semin
2020-05-28 19:53 ` Serge Semin
2020-05-28 20:38 ` Andy Shevchenko
2020-05-26 22:50 ` [PATCH v3 10/10] dmaengine: dw: Initialize max_sg_nents with nollp flag Serge Semin
2020-05-28 14:56 ` Andy Shevchenko
2020-05-28 15:50 ` Serge Semin
2020-05-28 20:31 ` Andy Shevchenko [this message]
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