linux-kernel - RE: [PATCH v2 05/12] cxl/acpi: Improve debug messages in cxl_acpi

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Date:   Thu, 20 Oct 2022 18:00:15 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Robert Richter <rrichter@....com>,
        Alison Schofield <alison.schofield@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        "Ira Weiny" <ira.weiny@...el.com>,
        Ben Widawsky <bwidawsk@...nel.org>,
        "Dan Williams" <dan.j.williams@...el.com>
CC:     <linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        "Davidlohr Bueso" <dave@...olabs.net>,
        Robert Richter <rrichter@....com>
Subject: RE: [PATCH v2 05/12] cxl/acpi: Improve debug messages in
 cxl_acpi_probe()

Robert Richter wrote:
> In cxl_acpi_probe() the iterator bus_for_each_dev() walks through all
> CXL hosts. Since all dev_*() debug messages point to the ACPI0017
> device which is the CXL root for all hosts, the device information is
> pointless as it is always the same device. Change this to use the host
> device for this instead.
> 
> Also, add additional host specific information such as CXL support,
> UID and CHBCR.
> 
> This is an example log:
> 
>  acpi ACPI0016:00: UID found: 4
>  acpi ACPI0016:00: CHBCR found: 0x28090000000
>  acpi ACPI0016:00: dport added to root0
>  acpi ACPI0016:00: host-bridge: ACPI0016:00
>   pci0000:7f: host supports CXL
> 
> Signed-off-by: Robert Richter <rrichter@....com>
> ---
>  drivers/cxl/acpi.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
> index 31e104f0210f..fb9f72813067 100644
> --- a/drivers/cxl/acpi.c
> +++ b/drivers/cxl/acpi.c
> @@ -221,6 +221,8 @@ static int add_host_bridge_uport(struct device *match, void *arg)
>  	if (IS_ERR(port))
>  		return PTR_ERR(port);
>  
> +	dev_info(pci_root->bus->bridge, "host supports CXL\n");
> +

I generally advocate for drivers to be silent, but this is a fundamental
message in a place that is helpful to indicate whether platform-firmware
is doing its job correctly, and it's only once per host bridge.

Applied for v6.2.