[Bug 254190] graphics/drm-kmod: I get corruption at the top of all of my consoles

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=254190

--- Comment #8 from Steven Friedrich <Steven.E.Friedrich at Gmail.com> ---
As an old hardware guy, I was curious when I saw this message:
"unknown: memory range not supported"

and this device:
none0 at pci0:0:20:2:      class=0x050000 card=0x72708086 chip=0xa36f8086 rev=0x10
hdr=0x00
    vendor     = 'Intel Corporation'
    device     = 'Cannon Lake PCH Shared SRAM'
    class      = memory
    subclass   = RAM

I thought, what is that?  Well I found a rather opaque description in an Intel
document at:
https://www.intel.com/content/dam/www/public/us/en/documents/technical-specifications/300-series-chipset-on-package-pch-datasheet-vol-1.pdf

21.7.2   SRAM
The local SRAM is used for ISH FW code storage and to read/write operational
data.  The local SRAM block includes both the physical SRAM as well as the
controller logic.  The SRAM is a total of 640 kbytes organized into banks of 32
kB each and is 32-bit wide.  The SRAM is shared with Intel CSME as shareable
memory.  To protect against memory errors, the SRAM includes ECC support.  The
ECC mechanism is able to detect multi-bit errors and correct for single bit
errors.  The ISH firmware has the ability to put unused SRAM banks into lower
power states to reduce power consumption.

That sounds to me like memory Intel uses between their OWN devices.
I would hope you would contact technical support at Intel and get clarification
of whether you should be ignoring this memory range and leave it untouched.

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