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From: Dave Jiang <dave.jiang@intel.com>
To: linux-cxl@vger.kernel.org,
	linux-pci@vger.kernel.org
Cc: dan.j.williams@intel.com,
	ira.weiny@intel.com,
	vishal.l.verma@intel.com,
	alison.schofield@intel.com,
	Jonathan.Cameron@huawei.com,
	dave@stgolabs.net
Subject: [PATCH v5 0/2] cxl: Region bandwidth calculation for targets with
 shared upstream link
Date: Tue, 18 Jun 2024 16:16:39 -0700
Message-ID: <20240618231730.2533819-1-dave.jiang@intel.com>
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v5:
- Adjust calculation of RPs under HB to only active RPs (Jonathan)
- See patches for specific change log

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 trasverses 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))))