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From: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
To: Wolfram Sang <wsa@the-dreams.de>
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 09:46:08 +0000
Message-ID: <OSBPR01MB3174B96296BFFA408F1C901FD80F0@OSBPR01MB3174.jpnprd01.prod.outlook.com> (raw)
In-Reply-To: <20190513090054.GA15744@kunai>

Hi Wolfram-san,

> From: Wolfram Sang, Sent: Monday, May 13, 2019 6:01 PM
> 
> Hi Shimoda-san,
> 
> thank you for this update!
> 
> > +static void renesas_sdhi_init_card(struct mmc_host *mmc, struct mmc_card *card)
> > +{
> > +	struct tmio_mmc_host *host = mmc_priv(mmc);
> > +
> > +	if (host->pdev->dev.iommu_group &&
> 
> I wonder if I am too cautious, but maybe we should have another
> condition here to be checked first, namely "host->mmc->max_segs < 512"?

I got it. I'll fix it on v3 patch.

> > +	    (mmc_card_mmc(card) || mmc_card_sd(card)))
> > +		host->mmc->max_segs = 512;
> > +	else
> > +		host->mmc->max_segs = host->pdata->max_segs;
> 
> max_segs can be 0, so we should probably have:
> 
>  +		host->mmc->max_segs = host->pdata->max_segs ?: 32;

Thank you for the point! I'll fix it on v3 patch.

> 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.

Best regards,
Yoshihiro Shimoda

> Kind regards,
> 
>    Wolfram


  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 [this message]
2019-05-13 11:34       ` Yoshihiro Shimoda
2019-05-13 13:54         ` Wolfram Sang
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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