Hi Wolfram-san again,
> From: Yoshihiro Shimoda, Sent: Monday, May 13, 2019 6:46 PM
>
> 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.
I'm afraid but I misunderstood this condition is "host->pdata->max_segs", not "host->mmc->max_segs",
to avoid small max_segs value than pdata->max_segs? (No one has such max_segs value at the moment though.)
If we use "host->mmc->max_segs", the max_segments value will be toggled by connecting/disconnecting a card like below:
(a card is connected)
# cat /sys/block/mmcblk0/queue/max_segments
512
(a card is disconnected and connected again)
# cat /sys/block/mmcblk0/queue/max_segments
1
(a card is disconnected and connected again)
# cat /sys/block/mmcblk0/queue/max_segments
512
...
Best regards,
Yoshihiro Shimoda
> > > + (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
