Re: [PATCH v8 7/9] PCI: endpoint: pci-epf-vntb: Reuse pre-exposed doorbells and IRQ flags

On Tue, Feb 17, 2026 at 11:54:29AM -0500, Frank Li wrote:
> On Tue, Feb 17, 2026 at 05:05:59PM +0900, Koichiro Den wrote:
> > Support doorbell backends where the doorbell target is already exposed
> > via a platform-owned fixed BAR mapping and/or where the doorbell IRQ
> > must be requested with specific flags.
> >
> > When pci_epf_alloc_doorbell() provides db_msg[].bar/offset, reuse the
> > pre-exposed BAR window and skip programming a new inbound mapping. Also
> > honor db_msg[].irq_flags when requesting the doorbell IRQ.
> >
> > Multiple doorbells may share the same Linux IRQ. Avoid duplicate
> > request_irq() calls by requesting each unique virq once.
> >
> > This makes pci-epf-vntb work with platform-defined or embedded doorbell
> 
> Nit: Make pci-epf-vntb work with ...
> 
> > backends without exposing backend-specific details to the consumer
> > layer.
> >
> > Signed-off-by: Koichiro Den <[email protected]>
> > ---
> > Changes since v7:
> >   - Deduplicate request_irq()/free_irq() calls based on virq (shared
> >     IRQ) rather than doorbell type.
> >
> >  drivers/pci/endpoint/functions/pci-epf-vntb.c | 61 ++++++++++++++++++-
> >  1 file changed, 58 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/pci/endpoint/functions/pci-epf-vntb.c b/drivers/pci/endpoint/functions/pci-epf-vntb.c
> > index 52cf442ca1d9..b1e8414c4e43 100644
> > --- a/drivers/pci/endpoint/functions/pci-epf-vntb.c
> > +++ b/drivers/pci/endpoint/functions/pci-epf-vntb.c
> > @@ -134,6 +134,11 @@ struct epf_ntb {
> >  	u16 vntb_vid;
> >
> >  	bool linkup;
> > +
> > +	/*
> > +	 * True when doorbells are interrupt-driven (MSI or embedded), false
> > +	 * when polled.
> > +	 */
> >  	bool msi_doorbell;
> >  	u32 spad_size;
> >
> > @@ -517,6 +522,17 @@ static int epf_ntb_configure_interrupt(struct epf_ntb *ntb)
> >  	return 0;
> >  }
> >
> > +static bool epf_ntb_db_irq_is_first(const struct pci_epf *epf, unsigned int idx)
> 
> epf_ntb_db_irq_is_duplicated() look better, below 'if' needn't !

Agreed. I'll rename it and update the usage in the next revision.

Thanks for the review,
Koichiro

> 
> Frank
> 
> > +{
> > +	unsigned int i;
> > +
> > +	for (i = 0; i < idx; i++)
> > +		if (epf->db_msg[i].virq == epf->db_msg[idx].virq)
> > +			return false;
> > +
> > +	return true;
> > +}
> > +
> >  static int epf_ntb_db_bar_init_msi_doorbell(struct epf_ntb *ntb,
> >  					    struct pci_epf_bar *db_bar,
> >  					    const struct pci_epc_features *epc_features,
> > @@ -533,9 +549,24 @@ static int epf_ntb_db_bar_init_msi_doorbell(struct epf_ntb *ntb,
> >  	if (ret)
> >  		return ret;
> >
> > +	/*
> > +	 * The doorbell target may already be exposed by a platform-owned fixed
> > +	 * BAR. In that case, we must reuse it and the requested db_bar must
> > +	 * match.
> > +	 */
> > +	if (epf->db_msg[0].bar != NO_BAR && epf->db_msg[0].bar != barno) {
> > +		ret = -EINVAL;
> > +		goto err_free_doorbell;
> > +	}
> > +
> >  	for (req = 0; req < ntb->db_count; req++) {
> > +		/* Avoid requesting duplicate handlers */
> > +		if (!epf_ntb_db_irq_is_first(epf, req))
> > +			continue;
> > +
> >  		ret = request_irq(epf->db_msg[req].virq, epf_ntb_doorbell_handler,
> > -				  0, "pci_epf_vntb_db", ntb);
> > +				  epf->db_msg[req].irq_flags, "pci_epf_vntb_db",
> > +				  ntb);
> >
> >  		if (ret) {
> >  			dev_err(&epf->dev,
> > @@ -545,6 +576,22 @@ static int epf_ntb_db_bar_init_msi_doorbell(struct epf_ntb *ntb,
> >  		}
> >  	}
> >
> > +	if (epf->db_msg[0].bar != NO_BAR) {
> > +		for (i = 0; i < ntb->db_count; i++) {
> > +			msg = &epf->db_msg[i].msg;
> > +
> > +			if (epf->db_msg[i].bar != barno) {
> > +				ret = -EINVAL;
> > +				goto err_free_irq;
> > +			}
> > +
> > +			ntb->reg->db_data[i] = msg->data;
> > +			ntb->reg->db_offset[i] = epf->db_msg[i].offset;
> > +		}
> > +		goto out;
> > +	}
> > +
> > +	/* Program inbound mapping for the doorbell */
> >  	msg = &epf->db_msg[0].msg;
> >
> >  	high = 0;
> > @@ -591,6 +638,7 @@ static int epf_ntb_db_bar_init_msi_doorbell(struct epf_ntb *ntb,
> >  		ntb->reg->db_offset[i] = offset;
> >  	}
> >
> > +out:
> >  	ntb->reg->db_entry_size = 0;
> >
> >  	ntb->msi_doorbell = true;
> > @@ -598,9 +646,13 @@ static int epf_ntb_db_bar_init_msi_doorbell(struct epf_ntb *ntb,
> >  	return 0;
> >
> >  err_free_irq:
> > -	for (req--; req >= 0; req--)
> > +	for (req--; req >= 0; req--) {
> > +		if (!epf_ntb_db_irq_is_first(epf, req))
> > +			continue;
> >  		free_irq(epf->db_msg[req].virq, ntb);
> > +	}
> >
> > +err_free_doorbell:
> >  	pci_epf_free_doorbell(ntb->epf);
> >  	return ret;
> >  }
> > @@ -666,8 +718,11 @@ static void epf_ntb_db_bar_clear(struct epf_ntb *ntb)
> >  	if (ntb->msi_doorbell) {
> >  		int i;
> >
> > -		for (i = 0; i < ntb->db_count; i++)
> > +		for (i = 0; i < ntb->db_count; i++) {
> > +			if (!epf_ntb_db_irq_is_first(ntb->epf, i))
> > +				continue;
> >  			free_irq(ntb->epf->db_msg[i].virq, ntb);
> > +		}
> >  	}
> >
> >  	if (ntb->epf->db_msg)
> > --
> > 2.51.0
> >