linux-kernel - Re: mmc does not work in qemu n900

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Date:	Sun, 8 Feb 2015 00:02:57 +0100
From:	Pali Rohár <pali.rohar@...il.com>
To:	Pavel Machek <pavel@....cz>
Cc:	Aaro Koskinen <aaro.koskinen@....fi>,
	Chris Ball <chris@...ntf.net>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
	Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>,
	Sebastian Reichel <sre@...nel.org>
Subject: Re: mmc does not work in qemu n900

On Friday 30 January 2015 15:23:34 Pali Rohár wrote:
> On Tuesday 27 January 2015 10:17:39 Pali Rohár wrote:
> > On Tuesday 27 January 2015 00:21:04 Aaro Koskinen wrote:
> > > Hi,
> > > 
> > > On Mon, Jan 26, 2015 at 10:04:59PM +0100, Pali Rohár wrote:
> > > > problem? Why any of these two patches fix problem when
> > > > mmc is not detected by kernel in qemu (machine n900)?
> > > > Detection of mmc fails because function
> > > > mmc_send_op_cond() without one of above patches fails.
> > > 
> > > Has it ever worked? It could be just that QEMU's emulation
> > > is broken. Since the kernel works on actual HW, you
> > > probably should contact QEMU maintainers.
> > > 
> > > I don't see n900 in Debian's QEMU. There's n800 and n810
> > > but I couldn't boot any of my kernels with those...
> > > 
> > > A.
> > 
> > It worked with stock Nokia kernel (2.6.28).
> > 
> > N900 qemu support is not in upstream qemu project, but in
> > linaro qemu version. You can find it e.g. in ubuntu:
> > http://packages.ubuntu.com/source/precise-updates/qemu-linar
> > o
> 
> Here is another alternative patch which enable internal eMMC
> support in qemu n900:
> 
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index 9584bff..225df49 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -2330,13 +2330,13 @@ static int mmc_rescan_try_freq(struct
> mmc_host *host, unsigned freq)
>  	sdio_reset(host);
>  	mmc_go_idle(host);
> 
> -	mmc_send_if_cond(host, host->ocr_avail);
> -
> -	/* Order's important: probe SDIO, then SD, then MMC */
> -	if (!mmc_attach_sdio(host))
> -		return 0;
> -	if (!mmc_attach_sd(host))
> -		return 0;
> +//	mmc_send_if_cond(host, host->ocr_avail);
> +//
> +//	/* Order's important: probe SDIO, then SD, then MMC */
> +//	if (!mmc_attach_sdio(host))
> +//		return 0;
> +//	if (!mmc_attach_sd(host))
> +//		return 0;
>  	if (!mmc_attach_mmc(host))
>  		return 0;
> 
> It just disable SDIO and SD code. It looks like using some
> SDIO or SD commands on mmc controller in qemu cause
> problems...
> 
> Any idea?

Pavel, see this email thread:
http://www.spinics.net/lists/linux-mmc/msg30424.html

You had problem with mounting mmc device as rootfs on (real) 
Nokia N900. Can you test one of those 3 patches which I sent to 
this email thread? If it change something for your kernel or 
userspace? I would like to know if I found another bug in qemu or 
same as you had...

-- 
Pali Rohár
pali.rohar@...il.com

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