linux-kernel - Re: [PATCH v7 01/27] cxl/acpi: Probe RCRB later during RCH downstream port creation

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Message-ID: <649896e15db5a_1dff294b2@dwillia2-mobl3.amr.corp.intel.com.notmuch>
Date:   Sun, 25 Jun 2023 12:34:57 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Terry Bowman <terry.bowman@....com>, <alison.schofield@...el.com>,
        <vishal.l.verma@...el.com>, <ira.weiny@...el.com>,
        <bwidawsk@...nel.org>, <dan.j.williams@...el.com>,
        <dave.jiang@...el.com>, <Jonathan.Cameron@...wei.com>,
        <linux-cxl@...r.kernel.org>
CC:     <terry.bowman@....com>, <rrichter@....com>,
        <linux-kernel@...r.kernel.org>, <bhelgaas@...gle.com>
Subject: Re: [PATCH v7 01/27] cxl/acpi: Probe RCRB later during RCH
 downstream port creation

Terry Bowman wrote:
> From: Robert Richter <rrichter@....com>
> 
> The RCRB is extracted already during ACPI CEDT table parsing while the
> data of this is needed not earlier than dport creation. This
> implementation comes with drawbacks: During ACPI table scan there is
> already MMIO access including mapping and unmapping, but only ACPI
> data should be collected here. The collected data must be transferred
> through a couple of interfaces until it is finally consumed when
> creating the dport. This causes complex data structures and function
> interfaces. Additionally, RCRB parsing will be extended to also
> extract AER data, it would be much easier do this at a later point
> during port and dport creation when the data structures are available
> to hold that data.
> 
> To simplify all that, probe the RCRB at a later point during RCH
> downstream port creation. Change ACPI table parser to only extract the
> base address of either the component registers or the RCRB. Parse and
> extract the RCRB in devm_cxl_add_rch_dport().
> 
> This is in preparation to centralize all RCRB scanning.

This patch by itself causes cxl_test build bisection breakage:

depmod: ERROR: Cycle detected: cxl_mock -> cxl_core -> cxl_mock
depmod: ERROR: Cycle detected: encrypted_keys
depmod: ERROR: Found 2 modules in dependency cycles!
make: *** [Makefile:1956: modules_install] Error 1

...so I will just squash it with the next patch and add a
co-developed-by.