From: Sudeep Holla <sudeep.holla@arm.com>
To: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, coresight@lists.linaro.org,
suzuki.poulose@arm.com,
Ganapatrao Kulkarni <gankulkarni@os.amperecomputing.com>,
Steve Clevenger <scclevenger@os.amperecomputing.com>,
Rob Herring <robh+dt@kernel.org>,
Frank Rowand <frowand.list@gmail.com>,
Russell King <linux@armlinux.org.uk>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"Rafael J. Wysocki" <rafael@kernel.org>,
Len Brown <lenb@kernel.org>, Sudeep Holla <sudeep.holla@arm.com>,
Lorenzo Pieralisi <lpieralisi@kernel.org>,
Mathieu Poirier <mathieu.poirier@linaro.org>,
Mike Leach <mike.leach@linaro.org>, Leo Yan <leo.yan@linaro.org>,
devicetree@vger.kernel.org, linux-acpi@vger.kernel.org
Subject: Re: [PATCH V4 0/6] coresight: etm4x: Migrate ACPI AMBA devices to platform driver
Date: Tue, 23 May 2023 16:51:59 +0100 [thread overview]
Message-ID: <20230523155159.na2wfhuhb7fqr3cy@bogus> (raw)
In-Reply-To: <20230523044553.1525048-1-anshuman.khandual@arm.com>
On Tue, May 23, 2023 at 10:15:47AM +0530, Anshuman Khandual wrote:
> CoreSight ETM4x devices could be accessed either via MMIO (handled via
> amba_driver) or CPU system instructions (handled via platform driver). But
> this has the following issues :
>
> - Each new CPU comes up with its own PID and thus we need to keep on
> adding the "known" PIDs to get it working with AMBA driver. While
> the ETM4 architecture (and CoreSight architecture) defines way to
> identify a device as ETM4. Thus older kernels won't be able to
> "discover" a newer CPU, unless we add the PIDs.
>
> - With ACPI, the ETM4x devices have the same HID to identify the device
> irrespective of the mode of access. This creates a problem where two
> different drivers (both AMBA based driver and platform driver) would
> hook into the "HID" and could conflict. e.g., if AMBA driver gets
> hold of a non-MMIO device, the probe fails. If we have single driver
> hooked into the given "HID", we could handle them seamlessly,
> irrespective of the mode of access.
>
> - CoreSight is heavily dependent on the runtime power management. With
> ACPI, amba_driver doesn't get us anywhere with handling the power
> and thus one need to always turn the power ON to use them. Moving to
> platform driver gives us the power management for free.
>
> Due to all of the above, we are moving ACPI MMIO based etm4x devices to be
> supported via tha platform driver. The series makes the existing platform
> driver generic to handle both type of the access modes. Although existing
> AMBA driver would still continue to support DT based etm4x MMIO devices.
> Although some problems still remain, such as manually adding PIDs for all
> new AMBA DT based devices.
>
> The series applies on 6.4-rc3.
>
Tested on Juno with some hacked up UEFI f/w.
Tested-by: Sudeep Holla <sudeep.holla@arm.com>
--
Regards,
Sudeep
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
prev parent reply other threads:[~2023-05-23 15:52 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-23 4:45 [PATCH V4 0/6] coresight: etm4x: Migrate ACPI AMBA devices to platform driver Anshuman Khandual
2023-05-23 4:45 ` [PATCH V4 1/6] coresight: etm4x: Allocate and device assign 'struct etmv4_drvdata' earlier Anshuman Khandual
2023-05-23 4:45 ` [PATCH V4 2/6] coresight: etm4x: Drop iomem 'base' argument from etm4_probe() Anshuman Khandual
2023-05-23 4:45 ` [PATCH V4 3/6] coresight: etm4x: Drop pid " Anshuman Khandual
2023-05-23 4:45 ` [PATCH V4 4/6] coresight: etm4x: Change etm4_platform_driver driver for MMIO devices Anshuman Khandual
2023-05-23 15:15 ` Sudeep Holla
2023-05-25 21:23 ` Suzuki K Poulose
2023-05-29 2:50 ` Anshuman Khandual
2023-05-23 4:45 ` [PATCH V4 5/6] coresight: platform: acpi: Ignore the absence of graph Anshuman Khandual
2023-05-23 4:45 ` [PATCH V4 6/6] coresight: etm4x: Add ACPI support in platform driver Anshuman Khandual
2023-05-23 15:51 ` Sudeep Holla [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20230523155159.na2wfhuhb7fqr3cy@bogus \
--to=sudeep.holla@arm.com \
--cc=anshuman.khandual@arm.com \
--cc=coresight@lists.linaro.org \
--cc=devicetree@vger.kernel.org \
--cc=frowand.list@gmail.com \
--cc=gankulkarni@os.amperecomputing.com \
--cc=gregkh@linuxfoundation.org \
--cc=lenb@kernel.org \
--cc=leo.yan@linaro.org \
--cc=linux-acpi@vger.kernel.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux@armlinux.org.uk \
--cc=lpieralisi@kernel.org \
--cc=mathieu.poirier@linaro.org \
--cc=mike.leach@linaro.org \
--cc=rafael@kernel.org \
--cc=robh+dt@kernel.org \
--cc=scclevenger@os.amperecomputing.com \
--cc=suzuki.poulose@arm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox