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    SubjectRe: [Patch 1/1 v5] via-sdmmc: VIA MSP card reader driver support
    Dear Joseph, Pierre and others.

    Since the driver has still not made any progress in recent days, I took the
    liberty of "adopting" it. It can now be found in my linux-2.6-via.git
    repository under the via-vx855-sdmmc branch (gitweb at
    http://git.gnumonks.org/cgi-bin/gitweb.cgi?p=linux-2.6-via.git;a=shortlog;h=refs/heads/via-vx855-sdmmc)

    As you can see, there are five incremental patches compared to the last v5
    release that Joseph posted in April.

    On Wed, Apr 22, 2009 at 01:35:29AM +0800, JosephChan@via.com.tw wrote:

    > >> +nodata:
    > >> + if (cmd->opcode == MMC_STOP_TRANSMISSION)
    > >> + cmdctrl |= VIA_CRDR_SDCTRL_STOP;
    > > >+
    >
    > >I didn't check this part properly the last time. I'm assuming you're telling
    > >the hardware that this is a command that terminates a data transmission? If
    > >so, you cannot check the opcode like that. There might be other stop
    > >commands.
    > >What you need to do is to either pass another parameter to your function
    > >when you're calling it with data->stop, or simply have a test in there if
    > >cmd == data->stop (or mrq->stop, whichever is most convenient).
    >
    > OK, we will change to
    > if(cmd == host->mrq->stop)
    > cmdctrl |= VIA_CRDR_SDCTRL_STOP;

    done.

    > >> + else if (ios->clock >= 5000000)
    > >> + clock = PCI_CLK_8M;
    > >>+ else
    > >>+ clock = PCI_CLK_375K;
    > >>+
    >
    > > This looks a bit strange. Why are you not comparing with the clock
    > > frequency you'll be setting?
    >
    > Do you mean that we should check the current clock frequency before setting?
    > But our engineer thinks that the following lines can do that work normally
    > too: Any comment?

    Well, if the "PCI_CLK" line and the corresponding register actually 1:1
    correspond to the actual SD card clock rate, then

    > else if (ios->clock >= 5000000)
    > clock = PCI_CLK_8M;

    would mean we use 8MHz even at the time the MMC core stack asks us to only
    use 5MHz, whcih is a bug!

    I have fixed this in my git tree now.

    > >> + mmc->caps = MMC_CAP_4_BIT_DATA;
    >
    > > You also need to set the bits stating if the controller supports the
    > > high-speed SD and/or MMC mode, otherwise the core won't go over 25/20 MHz.
    >
    >
    > OK, we will add the following line in the via_init_mmc_host function:
    >
    > mmc->caps |= MMC_CAP_MMC_HIGHSPEED |MMC_CAP_SD_HIGHSPEED;

    Since I cannot see any indication from the VX800 / VX855 data sheet that HS-MMC
    is actually supported, I only use SD_HIGHSPEED for now.

    Joseph: Can you find out if the controller actually supports HS-MMC, not only
    SD highspeed?

    > org_data = readl(addrbase + VIA_CRDR_SDEXTCTRL);
    >
    > if ((ios->timing == MMC_TIMING_SD_HS) || (ios->timing == MMC_TIMING_MMC_HS))
    > org_data |= VIA_CRDR_SDEXTCTRL_HISPD;
    > else
    > org_data &= ~VIA_CRDR_SDEXTCTRL_HISPD;
    >
    > writel(org_data, addrbase + VIA_CRDR_SDEXTCTRL);

    tried that, unfortunately this is buggy, since org_data refers to SDBUSMODE rather than SDEXTCTRL. I've fixed it in this patch:
    http://git.gnumonks.org/cgi-bin/gitweb.cgi?p=linux-2.6-via.git;a=commitdiff;h=bb1f9f2d9d51bbf294ae036d02e2546f2d8b36c3

    The resulting driver runs so far fine on my VX855ES based board, but I'll give
    it some more testing before re-submitting the patch.

    There is also one case in the code where due to a DMA controller bug, we force
    the clock to 8MHz despite the MMC core requesting 375kHz. I think the proper
    fix here is to fall back on PIO (non-DMA) mode for 375kHz, rather than
    overclocking the poor card by more than 21 times.

    After that has been fixed, plus some more testing, I'll re-submit.

    Regards,
    --
    - Harald Welte <HaraldWelte@viatech.com> http://linux.via.com.tw/
    ============================================================================
    VIA Open Source Liaison


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