Mount root from SD card?
mav at FreeBSD.org
Tue Jan 20 11:58:37 PST 2009
M. Warner Losh wrote:
> In message: <20090120.122312.1543793985.imp at bsdimp.com>
> "M. Warner Losh" <imp at bsdimp.com> writes:
> : : IMHO it is incorrect to disable 4bit mode on that stage, it is too late
> : : there. It should be done at controller capabilities announcement stage.
> : : If you are not objecting, I would remove that wire4 variable.
> : I am objecting. The code is there so that the rest of the driver does
> : the right thing when doing 4-bit. It needs to be a capability too.
> : However, before we go monkeying with this, we need to find the
> : underlying bug.
> I've got the following patch, untested, that I think does what I think
> needs to be done. Not sure about the return value from update_ios...
> Index: at91_mci.c
> --- at91_mci.c (revision 187479)
> +++ at91_mci.c (working copy)
> @@ -201,7 +201,10 @@
> sc->host.f_min = 375000;
> sc->host.f_max = 30000000;
> sc->host.host_ocr = MMC_OCR_320_330 | MMC_OCR_330_340;
> - sc->host.caps = MMC_CAP_4_BIT_DATA;
> + if (sc->wire4)
> + sc->host.caps = MMC_CAP_4_BIT_DATA;
> + else
> + sc->host.caps = 0;
> child = device_add_child(dev, "mmc", 0);
> device_set_ivars(dev, &sc->host);
> err = bus_generic_attach(dev);
Ok. I agree with this part. If for some reason you really need this
wire4 variable, this is the right way to use it.
> @@ -295,6 +298,8 @@
> clkdiv = (at91_master_clock / ios->clock) / 2;
> if (ios->bus_width == bus_width_4 && sc->wire4)
> + return EINVAL;
> + if (ios->bus_width == bus_width_4)
> WR4(sc, MCI_SDCR, RD4(sc, MCI_SDCR) | MCI_SDCR_SDCBUS);
> WR4(sc, MCI_SDCR, RD4(sc, MCI_SDCR) & ~MCI_SDCR_SDCBUS);
This part is correct, but useless. If the first part have not set
MMC_CAP_4_BIT_DATA, then mmc layer will never request bus_width_4.
That's why I have proposed to remove " && sc->wire4" check from here.
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