Re: Black screen while resuming a SDXC (UHS) card (_mmc_sd_resume)

[Ulf Hansson <ulf.hansson@linaro.org>]

+ Adrian

On Thu, 23 Jan 2020 at 11:40, Tim Schumacher <tim@timakro.de> wrote:
>
> On 2019-09-06, Ulf Hansson wrote:
> > On Thu, 5 Sep 2019 at 22:01, Tim Schumacher <tim@timakro.de> wrote:
> > >
> > > Hi,
> > >
> > > I'm sending this old bug by mail since a lot of developers don't use
> > > bugzilla.
> > >
> > > Original bug report on bugzilla by Pedro Rodrigues from 2019-01-30:
> > >
> > > https://bugzilla.kernel.org/show_bug.cgi?id=202459
> > >
> > > > This bug can be found on a Lenovo Miix 320-10ICR
> > > >
> > > > When using a SDXC (UHS) card, the screen becomes black if
> > > > _mmc_sd_resume() is called. After some investigation, I found that an
> > > > UHS card uses 1.8 V for signalling while a normal SD card uses 3.3 V. By
> > > > forcing the SDXC to use 3.3 V the black screen does not appear. It seems
> > > > that during a _mmc_sd_resume function call, while claiming the host, an
> > > > I2C resume function is called based on an existing supplier link between
> > > > the I2C bus and the card device.  The problem is that if the signalling
> > > > voltage is configured to 1.8 V, during the I2C resume call, the screen
> > > > turns black.  I was able to fix this issue by setting the initial signal
> > > > voltage (3.3 V) before suspending the card, so that when the card is
> > > > resumed, the voltage is in the original state. To do this I added a
> > > > function call to mmc_set_initial_signal_voltage() during mmc_power_off
> > > > routine (drivers/mmc/core/core.c).  As I’m not an expert on Linux,  I’m
> > > > posting the issue and possible solution so that it could be implemented
> > > > on a future release.
> > > >
> > > > Please, share your thoughts :)
> > >
> > > I can't provide further insight but I'm interested if this is possibly
> > > the cause for the general issues people are having with the SD card
> > > reader on Lenovo Miix 320 devices.
> > >
> > > Those issues described in posts like
> > >
> > > https://vincent-ventures.com/2018/12/arch-linux-on-lenovo-ideapad-miix-320/
> > > https://esc.sh/blog/linux-on-lenovo-miix-320/
> > >
> > > are (1) black screen when booting with an SD card installed and (2) when
> > > inserting an SD card after booting it shows up but upon trying to access
> > > it the screen turns black until the card is removed again.
> > >
> > > I can confirm (1) on my Lenovo Miix 320-10ICR with kernel version
> > > 5.2.11. I can also confirm that only SDXC cards are affected, SD and
> > > SDHC cards work as expected.
> >
> > For the mmc community to help, you need to provide some kernel logs,
> > output from lspci, figure out what mmc host driver that is being used,
> > etc - in general collect more data. Then re-post the data to
> > linux-mmc, me and a potential mmc host driver maintainer (if there is
> > one). Yes, we can look into bugzilla as well, but first we need some
> > more overall info in an email.
> >
> > Most likely, if there is any response, you will be asked to test
> > patches. So you need to be able build and boot a new kernel, but I
> > guess you already know that part.
> >
> > Kind regards
> > Uffe
> >
>
> Hi, I'm coming back to this issue now. The issue is still present in
> kernel version 5.4.8.
>
> Kernel logs from boot with SD card and black screen: https://termbin.com/outp
> Kernel logs from boot without SD card: https://termbin.com/dc2y
>
> I couldn't find anything conspicuous in there, the card is working as
> expected. Only issue is the black screen (I'm doing these tests via SSH).
>
> lspci output: https://termbin.com/x452
>
> How do I figure out which mmc host driver is in use? I assume I'm
> looking for one of these https://github.com/torvalds/linux/tree/master/drivers/mmc/host
> I couldn't find anything like it in the kernel logs or from lsmod.
>
> Please read the original bug report by Pedro Rodrigues quoted above.
> He got to the technical core of the problem already and proposed a fix
> I assume could be understood, sanity checked and implemented by a mmc
> maintainer.

I have read the reports and browsed the data you provided. It seems
like this is an sdhci-acpi mmc/sd controller, Adrian Hunter (Intel
maintains this variant). There is one eMMC, which seems to work fine
and then the SD-card that you have inserted. The SD card looks like it
gets detected properly.

I don't see anything in the logs that stands out. However, I would try
a couple of different SD-cards, just to see what happens (if you have
more then one at hand). From that and going forward, I think I will
need to defer to Adrian's help. Perhaps we can put together some debug
patch for you to test, or so.

I will keep monitoring the discussion and fold in if there is anything
more I can help with.

Kind regards
Uffe