linux-kernel - Re: [PATCH v4 3/5] cxl/pci: Find and register CXL PMU devices

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Date:   Wed, 5 Apr 2023 11:48:05 +0100
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Dan Williams <dan.j.williams@...el.com>
CC:     Liang Kan <kan.liang@...ux.intel.com>, <linux-cxl@...r.kernel.org>,
        <peterz@...radead.org>, <mingo@...hat.com>, <acme@...nel.org>,
        <mark.rutland@....com>, <will@...nel.org>, <linuxarm@...wei.com>,
        <linux-perf-users@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Davidlohr Bueso <dave@...olabs.net>,
        Dave Jiang <dave.jiang@...el.com>
Subject: Re: [PATCH v4 3/5] cxl/pci: Find and register CXL PMU devices

On Tue, 4 Apr 2023 12:17:01 -0700
Dan Williams <dan.j.williams@...el.com> wrote:

> Jonathan Cameron wrote:
> > CXL PMU devices can be found from entries in the Register
> > Locator DVSEC.
> > 
> > In order to register the minimum number of IRQ vectors necessary
> > to support all CPMUs found, separate the registration into two
> > steps.  First find the devices, and query the IRQs used and then
> > register the devices. Between these two steps, request the
> > IRQ vectors necessary and enable bus master support.  
> 
> It's not clear why this patch is talking about irq vectors and bus
> mastering when there is no irq query/setup logic in this patch?
> 

> > Future IRQ users for CXL type 3 devices (e.g. DOEs) will need to
> > follow a similar pattern the number of vectors necessary is known
> > before any parts of the driver stack rely on their availability.  
> 
> With the new pci_msix_alloc_irq_at() it's not clear that this 2 step
> approach is required, right?

Stale description. Will drop all that garbage.

> 
> > Reviewed-by: Dave Jiang <dave.jiang@...el.com>
> > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> > ---
> > v4:
> > - No change.
> > ---
> >  drivers/cxl/core/Makefile |  1 +
> >  drivers/cxl/core/core.h   |  1 +
> >  drivers/cxl/core/cpmu.c   | 72 +++++++++++++++++++++++++++++++++++++++  
> 
> A quibble with the naming, I prefer:
> 
> drivers/cxl/core/pmu.c
> 
> ...since "cxl" is in the directory path. Also, usages of cpmu
> already have a cxl in their symbol names, so just s/cpmu/pmu/ throught.
> The usage of CPMU_ for register macros would seem be more clear, or at
> least more consistent, as CXL_PMU_ like the other register offset
> definitions in cxlpci.h.

Makes sense. I'll leave the register defs as
CPMU_XXX to keep them compact but use the pmu naming for pretty much everything else.

> 
> >  drivers/cxl/core/port.c   |  2 ++
> >  drivers/cxl/core/regs.c   | 16 +++++++++
> >  drivers/cxl/cpmu.h        | 56 ++++++++++++++++++++++++++++++  
> 
> drivers/cxl/pmu.h
> 
> >  drivers/cxl/cxl.h         | 14 ++++++++
> >  drivers/cxl/cxlpci.h      |  1 +
> >  drivers/cxl/pci.c         | 25 +++++++++++++-
> >  9 files changed, 187 insertions(+), 1 deletion(-)  
> 
> Other than those minor issues above, this looks good to me, with those
> fixed up.
> 
> Reviewed-by: Dan Williams <dan.j.williams@...el.com>
Thanks,