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Re : Waking up the AHCI device
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From: |
Paul Dufresne |
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Subject: |
Re : Waking up the AHCI device |
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Date: |
Sun, 07 Feb 2021 13:27:22 -0500 |
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User-agent: |
Zoho Mail |
---- Le dim., 07 févr. 2021 13:02:58 -0500 Paul Dufresne <dufresnep@zoho.com>
écrit ----
> I suspect CAP.SAM was 0 in previous versions... did not check.
> But that most computers now have CAP.SAM to 1, so that GHC.AE should be
> written, even if already to 1, to "wake up" the device.
> I suspect current implementation of AHCI in Mach does not it.
>
I guess I was confused there.
CAP.SAM means Supports AHCI mode only.
So if CAP.SAM=1, GHC.AhciEnable is read-only, and always to 1.
If CAP.SAM is 0, GHC.AhciEnable is writable, and 0 'by default'. Meaning no
commands should be sent to AHCI before putting it to 1.
BTW my main computer have no option to disable AHCI in firmware... but does
show the phy device offline error.
But don't know if CAP.SAM is really 1.