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Thread: [USEFUL] Interesting Bay Trail bug list. Possible Wifi/SD card issues...known?

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    [USEFUL] Interesting Bay Trail bug list. Possible Wifi/SD card issues...known?

    Document here http://www.intel.com/content/dam/www...pec-update.pdf

    It's Intel's full list of known problems, including description near the end of the document, and whether it is fixed in current steppings, planned to be fixed, no known solution or not planned to be fixed.

    A number of the SDIO VLTs may well be impacting functionality for someone people, depending on how the Broadcom drivers are handling things. I see some occurances, like VLT40 which summed up is that if the SDIO is using asynchronous interupts, it can cause it to fail to initialize, but asynchronous interupts are not typically used by OS drivers (which doesn't mean no one does it with their drivers).

    VLT55 SD Card UHS-I Mode is Not Fully Supported
    Problem: The SD Card Specification rev 3.01 Addendum 1 specifies a relaxed NCRC (Number of clocks to Cyclic Redundancy Check) timing specification for UHS-I (DDR50) mode. Due to this erratum, the SD Host Controller is not fully compatible with this relaxed timing specification.

    Implication: Using UHS-I mode with SD devices that rely upon relaxed NCRC may cause SD host commands to fail to complete, resulting in device access failures.
    BIOS and driver code changes have been identified and may be implemented as a workaround for this erratum.

    This actually may be why some people are having issues with micro SD cards in their T100, and it would imply issues in other bay trail based tablets/devices. UHS-I (DDR50) mode is what is used by ALL MICRO SD CARDS THAT ARE UHS-I! So if they also happen to be using NCRC, its likely not going to work. I am cross posting this in the micro SD card failure thread. Implication, you may well just be up a creek with your specific micro SD card and should try another one. This is not a T100 bug, this is a BAY TRAIL BUG! I'd assumed fixed in future Atom chips, but appears to be not planned to be fixed in future Bay Trail steppings.

    VLT60 Power-On Reset Sequence May Not Complete Under Certain Conditions
    Problem: Under certain conditions, the SoC may not complete initialization either during a reset issued while the system is running or from the G3 (mechanically off) global system state.

    Implication: When this erratum occurs, the SoC will detect an initialization problem and halt the initialization sequence prior to normal operation, leading to a system hang. The system will subsequently require a power cycle via the system power button.

    Workaround:A firmware workaround has been identified that significantly reduces the likelihood of this erratum for a reset issued while the system is running.

    THIS ONE EXPLAINS A LOT! I have noticed every once in awhile when reseting my T100, or rarer, when booting from off state, that it just doesn't boot. I have to hold down the power button for a hard reset, and then hit it for a normal boot. Its uncommon, especially if the device has been OFF for a bit. However, maybe 1 in 20 times I've just shut it down and then go to almost immediately turn it back on, it'll hang (as in fails to initialize at all, no web cam light, nothing), maybe about the same 1 in 20 on a regular reboot, it goes to screen blank and never comes back up. I have to hard reset with the power button and then boot it normally.

    A very interesting read through, though I've only skimmed the known problems.

    Oh if wondering, Intel has this for all their chips. Most issues tend to be relatively minor, obscure or are "one in a million". Occasionally an issue is a bit more common. For things like VLT60, it mentions a firmware workaround, I wonder when/if Asus will implement it in a future BIOS update.
    Tor and TonySon like this.

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    This is a useful post for those with these issues. I'm going to make this a "sticky" for everyone to easily find for a while.
    OWNER OF ASUS 64GB T100TA w/128GB microSD, and now running Windows 10

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    Also if anyone is curious by looking at the list, I wouldn't consider Bay Trail particularly more bugged than most other CPUs/SoCs.

    For example, here is Intel's published specification updates for Haswell.

    http://www.intel.com/content/dam/www...ion-update.pdf

    Its more just that, especially the one on SD card NCRC not supported correctly may be a bit more of a prominent issue (since we are up to 12 or so pages on the micro SD card help thread) and I can almost guarantee that the hung reboot/boot is something I have noticed on mine a number of times. The wifi is a bit more, "not sure", but there are several SDIO issues listed in the known problems and it is possible that if Broadcom isn't coding the drivers with it in mind, it may be what is impacting some T100 devices.

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    This little gem...

    VLT37 SDIO Host Controller Does Not Control The SDIO Bus Power
    Problem: The SD Bus Power bit in Power Control Register (Bus 0; Device 17; Function 0; Offset 029H) is not connected to any SOC IO pin that can reset the SDIO bus power. Due to this erratum, SDIO device Power-On-Reset cannot be controlled by Power Control Register. SDIO Controller may fail to comply with SD Host Controller Specification Version 3.00.

    Implication: SDIO devices may not be powered up and initialized correctly.
    Software should be configured to use a GPIO pin on the platform to enable or disable the SDIO bus power.

    I've found this and a couple of others that really sound like they could be driving a lot of the Wifi issues (other ones the SD card issues), a lot dependent upon how the drivers are written and the OS is working. Some of it very well may depend on the very specific device (not just model) that is used in the machine in question in regards to the micro SD card, or the SDIO wifi adpater.

    A large number of the issues have implications about "dependent upon driver implementation" and similar, or sometimes "BIOS workaround indicated"

  5. #5
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    Does any of this have anything to do with Bluetooth not staying connected.

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    Its a least possible. There are a few SDIO Bay Trail issues listed. That said, I'd think anything that would cause bluetooth problems, would also be causing wifi issues in general at the same time (as both are integrated in to the SDIO adapter). A number of them have to do with improper initialization of the SDIO adapter and/or failure to initialize depending on a few different things (mostly uncommon driver calls/modes that most drivers don't use).

    Most likely, from what I can see in the issues, if one of them is causing a bluetooth problem, the wifi should also be on the fritz at the same time.

    In theory. It may just be poor drivers and/or the SDIO adapter itself with an issue.

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    I confess to not being able to fully grok this issue, but this

    Quote Originally Posted by azazel1024 View Post
    THIS ONE EXPLAINS A LOT! I have noticed every once in awhile when reseting my T100, or rarer, when booting from off state, that it just doesn't boot. I have to hold down the power button for a hard reset, and then hit it for a normal boot. Its uncommon, especially if the device has been OFF for a bit. However, maybe 1 in 20 times I've just shut it down and then go to almost immediately turn it back on, it'll hang (as in fails to initialize at all, no web cam light, nothing), maybe about the same 1 in 20 on a regular reboot, it goes to screen blank and never comes back up. I have to hard reset with the power button and then boot it normally.
    is a relief to see. I'm glad to see that the cause of this is identified. Now I'm just keeping my fingers crossed for a BIOS update to rectify it.

    Is this the same issue that is casing the memory card slot to drain battery while the computer is in sleep?

    No, but one of the issues listed is that the SoC cannot disable power to the SD slot as no/default GPIO pins can control it. The solution is use a different method to power it down (I think tying the power to a different GPIO pin).

    That may be causing it, but that is a little more suspect as I'd suspect that would effect all T100's if Asus hadn't mitigated it (it does not seem mitigatable in software, but has to be done through hardware). There are a couple of others though that might point toward the micro SD card slot not being able to be properly powered off or reach minimum power states, that might be more of a firmware/driver issue. But again, seems like it would impact most/all units if the T100 suffered from it.

    Doesn't mean it doesn't impact only a few units though.

    The failing the boot issue I understand fully what Intel has written...but it seems a little...uh...devoid of causation in the issue report. Just simply that sometimes it fails to initialize during boot, sometimes, and requires a hard reset, a BIOS workaround is possible and allieviates the majority of the occurances.
    Last edited by azazel1024; 01-17-2014 at 12:51 PM.

 

 

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