Re: [PATCH V10 5/9] cxl/port: Find a DOE mailbox which supports CDAT

[Ira Weiny]

On Mon, Jun 06, 2022 at 10:48:19AM -0700, Ben Widawsky wrote:
> On 22-06-04 17:50:45, ira.weiny@xxxxxxxxx wrote:
> > From: Ira Weiny <ira.weiny@xxxxxxxxx>
> > 
> > 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@xxxxxxxxx>
> > Cc: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
> > Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx>
> > 
> > ---
> > 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
> >