Messages in this thread | | | Date | Tue, 6 Sep 2022 09:53:27 +0100 | From | Jonathan Cameron <> | Subject | Re: [PATCH 05/15] cxl/acpi: Add probe function to detect restricted CXL hosts in RCD mode |
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On Tue, 6 Sep 2022 09:19:49 +0200 Robert Richter <rrichter@amd.com> wrote:
> On 01.09.22 11:10:38, Jonathan Cameron wrote: > > On Thu, 1 Sep 2022 08:01:05 +0200 > > Robert Richter <rrichter@amd.com> wrote: > > > On 31.08.22 11:08:04, Jonathan Cameron wrote: > > > > On Wed, 31 Aug 2022 10:15:53 +0200 > > > > Robert Richter <rrichter@amd.com> wrote: > > > > > > The probe function is triggered by adding an own root device for RCHs. > > > > > This is different to CXL VH where an ACPI "ACPI0017" root device > > > > > exists. Its detection starts the CXL host detection. In RCD mode such > > > > > a device does not necessarily exists, so solve this by creating a > > > > > plain platform device that is not an ACPI device and is root only for > > > > > RCHs. > > > > > > > > If I read this correctly that platform device is created whether or not > > > > there are any cxl devices in the system? > > > > > > > > Can we create it only if we find some devices that will be placed > > > > under it later? > > > > > > This would move the host detection from probe to init which I wanted > > > to avoid to better control driver init order dependencies. > > > > It's a bit nasty either way. I can see your reasoning, but > > definitely not keen on it if there is a plausible way to avoid. > > > > > > I could add a put_device() at the end of a probe so that it will be > > > released in case no other references use it. This implies the refcount > > > is maintained for parent devices. Or this needs to be added to. So if > > > there are no children (hosts) attached to the root device after probe, > > > it will disappear. > > > > Unless there is precedence for that, it'll be weird enough to be > > hard to maintain. I guess I can live with the ugliness if we can't > > add something new to ACPI to base this off. > > Let's stay with a put_device() for now. Then, we wont have a stale cxl > root device in the system in case there are no RCD children. > > -Robert Kind of obvious, but... Make sure to call that out as an unusual thing to do via cover letter / patch description so we hopefully get more eyes on this detail..
Jonathan
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