Date: Tue, 20 Jan 2009 21:58:39 +0200 From: Alexander Motin <mav@FreeBSD.org> To: "M. Warner Losh" <imp@bsdimp.com> Cc: freebsd-arm@freebsd.org Subject: Re: Mount root from SD card? Message-ID: <49762CEF.1000405@FreeBSD.org> In-Reply-To: <20090120.123230.-272218744.imp@bsdimp.com> References: <20090120.114051.-854291995.imp@bsdimp.com> <4976215B.40302@FreeBSD.org> <20090120.122312.1543793985.imp@bsdimp.com> <20090120.123230.-272218744.imp@bsdimp.com>
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M. Warner Losh wrote: > In message: <20090120.122312.1543793985.imp@bsdimp.com> > "M. Warner Losh" <imp@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); > else > 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. -- Alexander Motin
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