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Date: Wed, 8 Jun 2022 12:39:49 -0700
From: Ira Weiny <ira.weiny@...el.com>
To: Ben Widawsky <bwidawsk@...nel.org>
CC: Dan Williams <dan.j.williams@...el.com>,
Bjorn Helgaas <bhelgaas@...gle.com>,
Jonathan Cameron <Jonathan.Cameron@...wei.com>,
Alison Schofield <alison.schofield@...el.com>,
Vishal Verma <vishal.l.verma@...el.com>,
Dave Jiang <dave.jiang@...el.com>,
<linux-kernel@...r.kernel.org>, <linux-cxl@...r.kernel.org>,
<linux-pci@...r.kernel.org>
Subject: Re: [PATCH V10 5/9] cxl/port: Find a DOE mailbox which supports CDAT
On Mon, Jun 06, 2022 at 10:48:19AM -0700, Ben Widawsky wrote:
> On 22-06-04 17:50:45, ira.weiny@...el.com wrote:
> > From: Ira Weiny <ira.weiny@...el.com>
> >
> > Each CXL device may have multiple DOE mailbox capabilities and each
> > mailbox may support multiple protocols. CXL port devices need to query
> > the CDAT information specifically.
> >
> > Search the DOE mailboxes for one which supports the CDAT protocol.
> > Cache that mailbox to be used for future queries.
> >
> > Only support memory devices at this time.
> >
> > Cc: Ben Widawsky <ben.widawsky@...el.com>
> > Cc: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> > Signed-off-by: Ira Weiny <ira.weiny@...el.com>
> >
> > ---
> > Changes from V9
> > Ben Widawsky
> > s/cxl_find_cdat_mb/cxl_cache_cdat_mb/; add kdoc
> > Jonathan Cameron
> > Move cache_cdat to port probe [Not 100% necessary but it
> > goes along with reading the cdat data.]
> >
> > Changes from V8
> > Incorporate feedback from Jonathan
> > Move all this to the cxl_port object
> >
> > Changes from V7
> > Minor code clean ups
> >
> > Changes from V6
> > Adjust for aux devices being a CXL only concept
> > Update commit msg.
> > Ensure devices iterated by auxiliary_find_device() are checked
> > to be DOE devices prior to checking for the CDAT
> > protocol
> > From Ben
> > Ensure reference from auxiliary_find_device() is dropped
> > ---
> > drivers/cxl/core/pci.c | 35 +++++++++++++++++++++++++++++++++++
> > drivers/cxl/cxl.h | 2 ++
> > drivers/cxl/cxlpci.h | 1 +
> > drivers/cxl/port.c | 2 ++
> > 4 files changed, 40 insertions(+)
> >
> > diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
> > index c4c99ff7b55e..d814d8317975 100644
> > --- a/drivers/cxl/core/pci.c
> > +++ b/drivers/cxl/core/pci.c
> > @@ -4,11 +4,14 @@
> > #include <linux/device.h>
> > #include <linux/delay.h>
> > #include <linux/pci.h>
> > +#include <linux/pci-doe.h>
> > #include <cxlpci.h>
> > #include <cxlmem.h>
> > #include <cxl.h>
> > #include "core.h"
> >
> > +#define CXL_DOE_PROTOCOL_TABLE_ACCESS 2
> > +
> > /**
> > * DOC: cxl core pci
> > *
> > @@ -458,3 +461,35 @@ int cxl_hdm_decode_init(struct cxl_dev_state *cxlds, struct cxl_hdm *cxlhdm)
> > return 0;
> > }
> > EXPORT_SYMBOL_NS_GPL(cxl_hdm_decode_init, CXL);
> > +
> > +/**
> > + * cxl_cache_cdat_mb() -- cache the DOE mailbox which suports the CDAT protocol
> > + *
> > + * @port: Port to containing DOE Mailboxes
> > + *
> > + * Cache a pointer to the doe mailbox which supports CDAT.
> > + */
> > +void cxl_cache_cdat_mb(struct cxl_port *port)
> > +{
> > + struct device *dev = port->uport;
> > + struct cxl_memdev *cxlmd;
> > + struct cxl_dev_state *cxlds;
> > + int i;
> > +
> > + if (!is_cxl_memdev(dev))
> > + return;
> > +
> > + cxlmd = to_cxl_memdev(dev);
> > + cxlds = cxlmd->cxlds;
> > +
> > + for (i = 0; i < cxlds->num_mbs; i++) {
> > + struct pci_doe_mb *cur = cxlds->doe_mbs[i];
> > +
> > + if (pci_doe_supports_prot(cur, PCI_DVSEC_VENDOR_ID_CXL,
> > + CXL_DOE_PROTOCOL_TABLE_ACCESS)) {
> > + port->cdat_mb = cur;
>
> What happens if cxl_pci is unloaded after this? Would it be better to copy out
> the CDAT info? Otherwise, I think you need to hold a ref on the PCI device
> (though I only took a quick look).
<sigh> I thought that could not happen but I see I was wrong.
A reference will need to be taken for at least the duration of the query.
Originally I had this set up to try and make it easier to query later. But I
think that is a waste ATM.
I'm going to rework this ownership.
Thanks for the review,
Ira
>
> > + return;
> > + }
> > + }
> > +}
> > +EXPORT_SYMBOL_NS_GPL(cxl_cache_cdat_mb, CXL);
> > diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> > index 140dc3278cde..0a86be589ffc 100644
> > --- a/drivers/cxl/cxl.h
> > +++ b/drivers/cxl/cxl.h
> > @@ -267,6 +267,7 @@ struct cxl_nvdimm {
> > * @component_reg_phys: component register capability base address (optional)
> > * @dead: last ep has been removed, force port re-creation
> > * @depth: How deep this port is relative to the root. depth 0 is the root.
> > + * @cdat_mb: Mailbox which supports the CDAT protocol
> > */
> > struct cxl_port {
> > struct device dev;
> > @@ -278,6 +279,7 @@ struct cxl_port {
> > resource_size_t component_reg_phys;
> > bool dead;
> > unsigned int depth;
> > + struct pci_doe_mb *cdat_mb;
> > };
> >
> > /**
> > diff --git a/drivers/cxl/cxlpci.h b/drivers/cxl/cxlpci.h
> > index fce1c11729c2..ddbb8b77752e 100644
> > --- a/drivers/cxl/cxlpci.h
> > +++ b/drivers/cxl/cxlpci.h
> > @@ -74,4 +74,5 @@ static inline resource_size_t cxl_regmap_to_base(struct pci_dev *pdev,
> > int devm_cxl_port_enumerate_dports(struct cxl_port *port);
> > struct cxl_dev_state;
> > int cxl_hdm_decode_init(struct cxl_dev_state *cxlds, struct cxl_hdm *cxlhdm);
> > +void cxl_cache_cdat_mb(struct cxl_port *port);
> > #endif /* __CXL_PCI_H__ */
> > diff --git a/drivers/cxl/port.c b/drivers/cxl/port.c
> > index 3cf308f114c4..04f3d1fc6e07 100644
> > --- a/drivers/cxl/port.c
> > +++ b/drivers/cxl/port.c
> > @@ -49,6 +49,8 @@ static int cxl_port_probe(struct device *dev)
> > if (IS_ERR(cxlhdm))
> > return PTR_ERR(cxlhdm);
> >
> > + cxl_cache_cdat_mb(port);
> > +
> > if (is_cxl_endpoint(port)) {
> > struct cxl_memdev *cxlmd = to_cxl_memdev(port->uport);
> > struct cxl_dev_state *cxlds = cxlmd->cxlds;
> > --
> > 2.35.1
> >
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