Re: [PATCH] mmc: core: Kioxia 016G01 does not enter boot mode after SLEEP

[Ulf Hansson]

On Tue, Jun 16, 2026 at 8:58 PM Kamal Dasu <kamal.dasu@xxxxxxxxxxxx> wrote:
>
>
>
> On Thu, Jun 11, 2026 at 5:53 PM Ulf Hansson <ulf.hansson@xxxxxxxxxxxxxxxx> wrote:
>>
>> On Tue, May 19, 2026 at 5:27 AM Florian Fainelli
>> <florian.fainelli@xxxxxxxxxxxx> wrote:
>> >
>> > On 5/12/26 06:33, Ulf Hansson wrote:
>> > > On Mon, 11 May 2026 at 18:01, Florian Fainelli
>> > > <florian.fainelli@xxxxxxxxxxxx> wrote:
>> > >>
>> > >> On 5/11/26 07:18, Ulf Hansson wrote:
>> > >>> On Mon, 13 Apr 2026 at 20:06, Florian Fainelli
>> > >>> <florian.fainelli@xxxxxxxxxxxx> wrote:
>> > >>>>
>> > >>>> The Kioxia 016G01 eMMC device does not exit SLEEP mode when sending CMD0
>> > >>>> which prevents the system from properly resuming from S3 warm boot where
>> > >>>> the eMMC is necessary to pull in the boot components.
>> > >>>
>> > >>> Is the bug confirmed by Kioxia?
>> > >>
>> > >> We've been going back and forth with them without much progress as far
>> > >> as a resolution goes. Since there was no progress and I would like to
>> > >> get this included in downstream kernels at some point, this was submitted.
>> > >>
>> > >>>
>> > >>> If not, can you explain a bit more what is actually happening during
>> > >>> system resume?
>> > >>
>> > >> Upon entering Suspend-to-DRAM, the eMMC will be put into sleep mode.
>> > >> When our systems resume, one of our hardware cores driving the eMMC (HIF
>> > >> block) in command mode will send a CMD0 command for the eMMC device to
>> > >
>> > > Is the CMD0 sent solely by HW/FW before the mmc core executes
>> > > _mmc_resume() during system resume?
>> >
>> > That is correct. The sequence basically goes like this: HW sends CMD0,
>> > then FW pulls in boot code, identifies this is a Suspend to DRAM, does
>> > its steps, and eventually Linux resumes and calls _mmc_resume().
>>
>> Okay, so it seems like this problem boils down to the fact that the FW
>> decides to send a CMD0 command for no good reason at system resume.
>> Unless I am missing a point here?
>>
> The JEDEC JESD84-B51 boot sequence is normative.
> The host sends CMD0 (0xF0F0F0F0 / GO_PRE_IDLE_STATE) to enter pre-idle/boot mode
> Broadcom mmc controller does not skip CMD0 and has no knowledge of the power
> State that the kernel left the device; it runs before DRAM is initialized and before Linux resumes,
> before any kernel state is accessible.

I understand the CMD0 generally works to wakeup/initialize the eMMC,
but that isn't really sufficient.

Please, consider these scenarios:
1) If the kernel decides to turn off clocks/regulators (VCC/VCCQ) at
suspend for the eMMC, then how does the FW know that it needs to
restore these before sending CMD0?
2) At resume the kernel wants to wake up the eMMC by sending a CMD5
(awake) instead of CMD0 (not implemented, but since it is faster we
may decide to add this at some point). If the FW already sent CMD0, a
CMD5 path would fail.

>
>
>>
>> The problem is that the FW doesn't know what low power state the
>> kernel decided to put the eMMC device into at system suspend, hence it
>> should really leave the decision to the kernel to wake up the eMMC at
>> system resume.
>>
>> Would it be possible to fix the FW instead?
>>
>> >
>> > >
>> > >> exit SLEEP mode. The Kioxia 016G01 device takes 10ms rather than the
>> > >> tSLEEP_EXIT value of 1ms which is advertised and so our HIF block does
>> > >
>> > > Can you please clarify what tSLEEP_EXIT refers to? Are you referring
>> > > to the S_A_TIMEOUT in the EXT_CSD register for the eMMC card?
>> >
>> > Yes, sorry I am referring to S_A_TIMEOUT in the EXT_CSD register.
>> >
>> > >
>> > > Anyway, waking up an eMMC from sleep state in just 1ms sounds a bit
>> > > optimistic to me.
>> >
>> > Fair enough, but AFAIR we wait up to 30ms before declaring a timeout,
>> > every other vendor we have seen exits and acknowledges boot within
>> > 1-10ms at most. Similarly if the device is not in SLEEP, then it
>> > acknowledges boot within 1ms.
>>
>> The S_A_TIMEOUT specifies the time the eMMC needs to complete the wake
>> up from its sleep state.
>>
>> If the device isn't in sleep state but fully powered-on (as it seems
>> to be what you have been playing with), the eMMC should just respond
>> immediately as with any other command when the eMMC is in "TRAN"
>> state. I assume that's why it works if we don't send the CMD5 (sleep)
>> command at system suspend.
>>
>> >
>> > >
>> > >> not see the Boot ACK pattern in time and does not service the read
>> > >> request from the processor that wanted to read from eMMC, we get a reset
>> > >> of the system, rather than continue booting.
>> > >>
>> > >> When SLEEP is not enabled, the eMMC device responds within tSLEEP_EXIT
>> > >> as advertised and we don't have that problem.
>> > >
>> > > Okay, I see.
>> > >
>> > > In this regard, it's important to understand for me how the mmc host
>> > > driver (and the HW/FW) manages VCC and VCCQ when the mmc core calls
>> > > mmc_power_off() from _mmc_suspend()?
>> > >
>> > > Does this turn off any of these regulators or what happens to them
>> > > during system suspend?
>> >
>> > We don't have software controlled regulators for VCC and VCCQ and our
>> > reference boards using that specific eMMC device keep it powered on
>> > through suspend-to-DRAM. This is the very reason why if it stays in
>> > sleep mode, powered on, and then we attempt to boot from eMMC we have
>> > this issue.
>>
>> Okay, thanks for elaborating.
>>
>> So you are mixing the system suspend/resume scenarios with boot here.
>> Is the problem for both?
>>
> No the problem only occurs when we suspend/resume if we put the device in suspend as per spec,
> subsequent resume fails.

Okay, thanks for clarifying!

>
>>
>> I understand the timeout problem, but not why the FW needs to send the
>> CMD0 to wake up the eMMC from system suspend. In regards to boot, that
>> is an entirely different scenario.
>>
>
> Vendor datasheets implementing JESD84-B51 quote from spec :
> "In the Sleep state, the power consumption of the memory device is minimized.
> In this state, the memory device reacts only to the commands RESET (CMD0 with
> argument of either 0x00000000 or 0xF0F0F0F0 or H/W reset) and SLEEP/AWAKE
> (CMD5). All other commands are ignored by the memory device."

Yes, that's correct but doesn't explain why the FW needs to send CMD0,
rather than relying on the kernel to do it.

>
>> Does the FW need to read something from the eMMC before the system
>> resumes? Or that is just during boot?
>
>
>   It's just booting up on resume and reads bootcode.

Would you mind elaborating what "reads bootcode" really means here? Is
it reading data from the eMMC?

To me, it looks like we may have two ways forward to fix this problem:
1) Fix the FW so it doesn't need to send the CMD0 at resume. If that
is possible, this would be the best option.
2) Instruct the kernel to keep the eMMC powered on at suspend, while
still doing a regular re-initialization of it at resume.

Kind regards
Uffe