Messages in this thread | | | Date | Wed, 11 Jan 2023 07:41:20 +0100 | From | Christoph Hellwig <> | Subject | Re: [PATCH 1/2] nvme-apple: Do not try to shut down the controller twice |
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On Wed, Jan 11, 2023 at 02:44:42PM +0900, Hector Martin wrote: > The higher-level resume path can't do a disable since the firmware isn't > up at that point, and the subsequent reset (which is shared with other > conditions that cause a reset) is what brings the firmware back up. So > the disable has to either happen in the suspend path, or in the shared > reset path after we know the firmware is running.
Ok, that's the weird part where nvme-apply really isn't nvme at all. Because for actual NVMe devices the register access must work all the time.
> That's only if you issue a disable *in lieu* of a shutdown (and in fact > if you do that on Apple controllers under some conditions, they crash). > Issuing a disable *after* a shutdown is required by the NVMe spec if you > want to use the controller again (and should basically do nothing at > that point, since the controller is already cleanly shut down, but it is > required to set EN to 0 such that the subsequent 0->1 transition > actually kickstarts the controller again). If you don't do that, the > controller never leaves the shutdown state (how would it know?).
Yes. Although I would not call this a disable after shutdown, but a disable (or rather reset) before using it again.
> To be clear, the sequence I was attempting to describe (which is what we > were doing before the patch that regressed this) was: > > (on sleep) > - NVMe shutdown > - NVMe disable > - Firmware shutdown > > After the firmware shutdown, we can't do anything with NVMe again until > we start firmware back up, which requires going through the reset flow. > > Right now we're doing: > > (on sleep) > - NVMe shutdown > - Firmware shutdown > (wakeup) > - Oops, NVMe is enabled, let's disable it! (times out due to FW being > down but failure isn't propagated) > - Firmware startup > - NVMe enable (thinks it succeeds but actually the controller is still > in the shutdown state since it was never disabled and this persists > across the firmware cycle!) > - I/O (never completes)
Yes, so I guess due to the weird firmware issues doing the disable after shutdown instead of before setting up might be the right thing for nvme-apple, unlike real NVMe. So I guess we need to do that in the driver, and add a big fat comment explaining why.
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