linux-kernel - Re: [PATCH V2 04/11] cxl/mem: Clear events on driver load

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Date:   Fri, 2 Dec 2022 08:34:02 -0800
From:   Ira Weiny <ira.weiny@...el.com>
To:     Dan Williams <dan.j.williams@...el.com>
CC:     Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Alison Schofield <alison.schofield@...el.com>,
        "Vishal Verma" <vishal.l.verma@...el.com>,
        Ben Widawsky <bwidawsk@...nel.org>,
        "Steven Rostedt" <rostedt@...dmis.org>,
        Davidlohr Bueso <dave@...olabs.net>,
        <linux-kernel@...r.kernel.org>, <linux-cxl@...r.kernel.org>
Subject: Re: [PATCH V2 04/11] cxl/mem: Clear events on driver load

On Thu, Dec 01, 2022 at 06:48:12PM -0800, Dan Williams wrote:
> cxl/mem is cxl_mem.ko, This is cxl/pci.
> 
> ira.weiny@ wrote:
> > From: Ira Weiny <ira.weiny@...el.com>
> > 
> > The information contained in the events prior to the driver loading can
> > be queried at any time through other mailbox commands.
> > 
> > Ensure a clean slate of events by reading and clearing the events.  The
> > events are sent to the trace buffer but it is not anticipated to have
> > anyone listening to it at driver load time.
> 
> This is easy to guarantee with modprobe policy, so I am not sure it is
> worth stating.

Fair enough.  But there was some discussion early on regarding why reading and
clearing on startup was a good thing.  This showed that we chose to do that and
why we don't care.  I'll remove it.

> 
> This breakdown feels odd. I would split the trace event definitions into
> its own lead in patch since that is a pile of definitions that can be
> merged on their own. Then squash get, clear, and this patch into one
> patch as they don't have much reason to go in separately.

I agree that splitting the Get/Clear/and this patch was odd.  However,
splitting Get/Clear made the discussion on those operations easier IMO.

As a result this did not really belong in either of those patches on their own.

It is also very clearly a do one thing per patch situation.

> 
> > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> > Reviewed-by: Dave Jiang <dave.jiang@...el.com>
> > Signed-off-by: Ira Weiny <ira.weiny@...el.com>
> > ---
> >  drivers/cxl/pci.c            | 2 ++
> >  tools/testing/cxl/test/mem.c | 2 ++
> >  2 files changed, 4 insertions(+)
> > 
> > diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
> > index 8f86f85d89c7..11e95a95195a 100644
> > --- a/drivers/cxl/pci.c
> > +++ b/drivers/cxl/pci.c
> > @@ -521,6 +521,8 @@ static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> >  	if (IS_ERR(cxlmd))
> >  		return PTR_ERR(cxlmd);
> >  
> > +	cxl_mem_get_event_records(cxlds);
> > +
> >  	if (resource_size(&cxlds->pmem_res) && IS_ENABLED(CONFIG_CXL_PMEM))
> >  		rc = devm_cxl_add_nvdimm(&pdev->dev, cxlmd);
> >  
> > diff --git a/tools/testing/cxl/test/mem.c b/tools/testing/cxl/test/mem.c
> > index aa2df3a15051..e2f5445d24ff 100644
> > --- a/tools/testing/cxl/test/mem.c
> > +++ b/tools/testing/cxl/test/mem.c
> > @@ -285,6 +285,8 @@ static int cxl_mock_mem_probe(struct platform_device *pdev)
> >  	if (IS_ERR(cxlmd))
> >  		return PTR_ERR(cxlmd);
> >  
> > +	cxl_mem_get_event_records(cxlds);
> > +
> 
> This hunk likely goes with the first patch that actually implements some
> mocked events.

If this patch was squashed into the other patches yes.  But as a patch which
does exactly 1 thing "Clear events on driver load" it works IMO.  I could just
have well put this patch at the very end.

Now that the Get/Clear operations are more settled I'll split this out and
squash it as you suggest.  Jonathan suggested squashing Get/Clear too but again
I really prefer the 1 thing/patch and each of those operations seemed like a
good breakdown.

Ira

> 
> >  	if (resource_size(&cxlds->pmem_res) && IS_ENABLED(CONFIG_CXL_PMEM))
> >  		rc = devm_cxl_add_nvdimm(dev, cxlmd);
> >  
> > -- 
> > 2.37.2
> > 
> 
>