Re: [PATCH v8 0/3] cxl: Region bandwidth calculation for targets with shared upstream link

Dan Williams
2024-09-21T10:27:17Z

Dave Jiang wrote:
> v8:
> - Fixed kbot warning
> - Fix checking incorrect return value (Alison)
> - Remove goto from cxl_region-shared_upstream_bandwidth_update() (Alison)
> - Add ** for kdoc comment (Alison)
> - Fixup documentation texts (Jonathan)
> - Rebase against v6.11-rc
>
> This series provides recalculation of the CXL region bandwidth when the targets have
> shared upstream link by walking the toplogy from bottom up and clamp the bandwdith
> as the code traverses up the tree. An example topology:
>
> An example topology from Jonathan:
>
> CFMWS 0
> |
> _________|_________
> | |
> ACPI0017-0 ACPI0017-1
> GP0/HB0/ACPI0016-0 GP1/HB1/ACPI0016-1
> | | | |
> RP0 RP1 RP2 RP3
> | | | |
> SW 0 SW 1 SW 2 SW 3
> | | | | | | | |
> EP0 EP1 EP2 EP3 EP4 EP5 EP6 EP7
>
> Computation for the example topology:
>
> Min (GP0 to CPU BW,
> Min(SW 0 Upstream Link to RP0 BW,
> Min(SW0SSLBIS for SW0DSP0 (EP0), EP0 DSLBIS, EP0 Upstream Link) +
> Min(SW0SSLBIS for SW0DSP1 (EP1), EP1 DSLBIS, EP1 Upstream link)) +
> Min(SW 1 Upstream Link to RP1 BW,
> Min(SW1SSLBIS for SW1DSP0 (EP2), EP2 DSLBIS, EP2 Upstream Link) +
> Min(SW1SSLBIS for SW1DSP1 (EP3), EP3 DSLBIS, EP3 Upstream link))) +
> Min (GP1 to CPU BW,
> Min(SW 2 Upstream Link to RP2 BW,
> Min(SW2SSLBIS for SW2DSP0 (EP4), EP4 DSLBIS, EP4 Upstream Link) +
> Min(SW2SSLBIS for SW2DSP1 (EP5), EP5 DSLBIS, EP5 Upstream link)) +
> Min(SW 3 Upstream Link to RP3 BW,
> Min(SW3SSLBIS for SW3DSP0 (EP6), EP6 DSLBIS, EP6 Upstream Link) +
> Min(SW3SSLBIS for SW3DSP1 (EP7), EP7 DSLBIS, EP7 Upstream link))))
>
> ---
>
> Dave Jiang (3):
> cxl: Preserve the CDAT access_coordinate for an endpoint
> cxl: Calculate region bandwidth of targets with shared upstream link
> cxl: Add documentation to explain the shared link bandwidth calculation

For the series:

Acked-by: Dan Williams <dan.j.williams@intel.com>

I still believe it should be possible to disperse this into port
enumeration code. On the other hand this is off on the side in cdat.c
and has no reason to wait another cycle for that feeling to be proven
out.

Forgive the delay in circling back to this.