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From: Wolfram Sang <wsa@the-dreams.de>
To: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Cc: "ulf.hansson@linaro.org" <ulf.hansson@linaro.org>,
	"wsa+renesas@sang-engineering.com"
	<wsa+renesas@sang-engineering.com>,
	"linux-mmc@vger.kernel.org" <linux-mmc@vger.kernel.org>,
	"linux-renesas-soc@vger.kernel.org" 
	<linux-renesas-soc@vger.kernel.org>
Subject: Re: [PATCH v2 2/2] mmc: renesas_sdhi: use multiple segments if possible
Date: Mon, 13 May 2019 15:54:20 +0200
Message-ID: <20190513135420.GB20443@kunai> (raw)
In-Reply-To: <OSBPR01MB3174B39C9BE0A725D4945D78D80F0@OSBPR01MB3174.jpnprd01.prod.outlook.com>

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Hi Shimoda-san,

> > > That also means, for the sys-dmac and Gen2, we then use 512 for the
> > > IOMMU case and 32 (default TMIO value) for the non IOMMU case. My
> > > understanding is that SYS DMAC can handle 512 in both cases. Maybe it
> > > makes sense then to make an incremental patch setting the max_segs value
> > > explicitly to 512 in the sys-dmac driver for Gen2?
> > 
> > I also think SYS DMAC can handle 512 segments. However, I'm not sure
> > it can improve the performance or not though. Anyway, an incremental patch
> > makes sense if needed, I think.
> 
> I measured the performance on R-Car H2 Lager. It seems 512 segments improve
> the sequential input to 5%. May I make an incremental patch on the patch series?
> What do you think?

Cool! I didn't expect that much of a performance improvement. My main
concern was understandable code because there was no "real reason" that
we once use 32 and once 512.

But if it causes even a performance improvement, even better :)

Yes, an incremental patch is a good idea.

Thanks for the work,

   Wolfram


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  reply index

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-13  4:29 [PATCH v2 0/2] mmc: renesas_sdhi: improve performance by using IOMMU Yoshihiro Shimoda
2019-05-13  4:29 ` [PATCH v2 1/2] mmc: tmio: No memory size limitation if runs on IOMMU Yoshihiro Shimoda
2019-05-13  4:29 ` [PATCH v2 2/2] mmc: renesas_sdhi: use multiple segments if possible Yoshihiro Shimoda
2019-05-13  9:00   ` Wolfram Sang
2019-05-13  9:46     ` Yoshihiro Shimoda
2019-05-13 11:34       ` Yoshihiro Shimoda
2019-05-13 13:54         ` Wolfram Sang [this message]
2019-05-14  6:05       ` Yoshihiro Shimoda
2019-05-21 21:57         ` Wolfram Sang
2019-05-22  5:11           ` Yoshihiro Shimoda

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