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
backends without exposing backend-specific details to the consumer
layer.

Signed-off-by: Koichiro Den <den@valinux.co.jp>
---
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)
+{
+	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

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 <den@valinux.co.jp>
> ---
> 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 !

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
>

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 <den@valinux.co.jp>
> > ---
> > 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
> >