On 11/05/2014 12:31 AM, Tim Kryger wrote:
On Tue, Nov 4, 2014 at 1:00 AM, Alexandre Courbot <acourbot@xxxxxxxxxx> wrote:
Hi Tim, thanks for your reply!
On 11/04/2014 02:28 PM, Tim Kryger wrote:
On Mon, Nov 3, 2014 at 7:05 PM, Alexandre Courbot <acourbot@xxxxxxxxxx>
wrote:
Hi guys,
On the NVIDIA shield (tegra114-roth) platform, I have noticed that MMC
stopped working completely on recent kernels. MMC devices will not show
up
and the message "mmc1: Controller never released inhibit bit(s)." shows
up
repeatedly in the console.
After bisecting I tracked commit 52221610dd84dc3e9196554f0292ca9e8ab3541d
("mmc: sdhci: Improve external VDD regulator support") as the one that
introduced this issue, which seems somehow surprising to me since it has
been around for a while and nobody else complained about this AFAICT.
I'm not too familiar with the Nvidia Shield so can you please confirm
the following?
The controller in the Tegra114 is SDHCI compliant and as such
sdhci_tegra_probe calls sdhci_add_host. External regulators are
sought in sdhci_add_host with a call to mmc_regulator_get_supply.
This is correct.
Since no external regulators are specified in tegra114.dtsi or
tegra114-roth.dts, mmc->supply.vmmc and mmc->supply.vqmmc are set to
-ENODEV.
Actually 2 of the MMC nodes in tegra114-roth.dts (for SD card and eMMC) have
a vmmc-supply property, so for two of them at least mmc->supply.vmmc is a
valid pointer.
I must have been looking at an old version of the file. Thanks for
clearing this up.
As explained above, vmmc is a valid pointer for 2 instances of the MMC
controller. Interestingly, if I just remove the "return" line in the
IS_ERR() block (without moving it around), the issue also seems to be fixed.
Can you provide the relevant parts of the log before the problem occurs?
There is not much unfortunately ; the only relevant log I have is this:
[ 12.246022] mmc2: Timeout waiting for hardware interrupt.
[ 12.264990] mmc2: Controller never released inhibit bit(s).
Some hardware interrupt timed out. I don't know much about the MMC
subsystem. but could it be because initially the controller is not in a
powered-on state, and that return statement causes the function to leave it
unpowered?
In a nutshell, the issue here is that the SDHCI spec demands that VMMC
be supplied by the controller itself with the specific voltage
configured using the SDHCI_POWER_CONTROL register but almost nobody
does this. Many SoCs omit this capability from their controllers and
instead rely upon external regulators. In such cases there isn't
normally any need to update the voltage bits of the power control
register. It sounds like you are saying this isn't true for the
Tegra114.
Thanks for your explanation, it makes sense now.
Looking at other Tegra boards .dts I noticed that SHIELD is the only one
using a vmmc-supply. Maybe this is the part that is wrong? I wrote this
DTS and cannot exclude I misread the schematics. Maybe that regulator is
used for some other (still sdmmc-related) purpose but the actual power
provider is the controller itself.
If you can confirm that the driver is performing as it should, I will
look in that direction and revise my DTS.
Thanks!
Alex.
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