diff mbox series

[12/23] cxl: Introduce endpoint decoders

Message ID 20211120000250.1663391-13-ben.widawsky@intel.com
State Superseded
Headers show
Series Add drivers for CXL ports and mem devices | expand

Commit Message

Ben Widawsky Nov. 20, 2021, 12:02 a.m. UTC
Endpoints have decoders too. It is useful to share the same
infrastructure from cxl_core. Endpoints do not have dports (downstream
targets), only the underlying physical medium. As a result, some special
casing is needed.

There is no functional change introduced yet as endpoints don't actually
enumerate decoders yet.

Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
---
 drivers/cxl/core/bus.c | 41 +++++++++++++++++++++++++++++++++--------
 1 file changed, 33 insertions(+), 8 deletions(-)

Comments

Jonathan Cameron Nov. 22, 2021, 4:20 p.m. UTC | #1
On Fri, 19 Nov 2021 16:02:39 -0800
Ben Widawsky <ben.widawsky@intel.com> wrote:

> Endpoints have decoders too. It is useful to share the same
> infrastructure from cxl_core. Endpoints do not have dports (downstream
> targets), only the underlying physical medium. As a result, some special
> casing is needed.
> 
> There is no functional change introduced yet as endpoints don't actually
> enumerate decoders yet.
> 
> Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>

I'm not a fan of special values like using 0 here to indicate endpoint
device.  I'd rather see a base cxl_decode_alloc(..., bool ep)
and possibly wrappers for the non ep case and ep one.

Jonathan

> ---
>  drivers/cxl/core/bus.c | 41 +++++++++++++++++++++++++++++++++--------
>  1 file changed, 33 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/cxl/core/bus.c b/drivers/cxl/core/bus.c
> index 1ee12a60f3f4..16b15f54fb62 100644
> --- a/drivers/cxl/core/bus.c
> +++ b/drivers/cxl/core/bus.c
> @@ -187,6 +187,12 @@ static const struct attribute_group *cxl_decoder_switch_attribute_groups[] = {
>  	NULL,
>  };
>  
> +static const struct attribute_group *cxl_decoder_endpoint_attribute_groups[] = {
> +	&cxl_decoder_base_attribute_group,
> +	&cxl_base_attribute_group,
> +	NULL,
> +};
> +
>  static void cxl_decoder_release(struct device *dev)
>  {
>  	struct cxl_decoder *cxld = to_cxl_decoder(dev);
> @@ -196,6 +202,12 @@ static void cxl_decoder_release(struct device *dev)
>  	kfree(cxld);
>  }
>  
> +static const struct device_type cxl_decoder_endpoint_type = {
> +	.name = "cxl_decoder_endpoint",
> +	.release = cxl_decoder_release,
> +	.groups = cxl_decoder_endpoint_attribute_groups,
> +};
> +
>  static const struct device_type cxl_decoder_switch_type = {
>  	.name = "cxl_decoder_switch",
>  	.release = cxl_decoder_release,
> @@ -208,6 +220,11 @@ static const struct device_type cxl_decoder_root_type = {
>  	.groups = cxl_decoder_root_attribute_groups,
>  };
>  
> +static bool is_endpoint_decoder(struct device *dev)
> +{
> +	return dev->type == &cxl_decoder_endpoint_type;
> +}
> +
>  bool is_root_decoder(struct device *dev)
>  {
>  	return dev->type == &cxl_decoder_root_type;
> @@ -499,7 +516,9 @@ static int decoder_populate_targets(struct cxl_decoder *cxld,
>   * cxl_decoder_alloc - Allocate a new CXL decoder
>   * @port: owning port of this decoder
>   * @nr_targets: downstream targets accessible by this decoder. All upstream
> - *		ports and root ports must have at least 1 target.
> + *		ports and root ports must have at least 1 target. Endpoint
> + *		devices will have 0 targets. Callers wishing to register an
> + *		endpoint device should specify 0.
>   *
>   * A port should contain one or more decoders. Each of those decoders enable
>   * some address space for CXL.mem utilization. A decoder is expected to be
> @@ -516,7 +535,7 @@ struct cxl_decoder *cxl_decoder_alloc(struct cxl_port *port,
>  	struct device *dev;
>  	int rc = 0;
>  
> -	if (nr_targets > CXL_DECODER_MAX_INTERLEAVE || nr_targets == 0)
> +	if (nr_targets > CXL_DECODER_MAX_INTERLEAVE)
>  		return ERR_PTR(-EINVAL);
>  
>  	cxld = kzalloc(struct_size(cxld, target, nr_targets), GFP_KERNEL);
> @@ -535,8 +554,11 @@ struct cxl_decoder *cxl_decoder_alloc(struct cxl_port *port,
>  	dev->parent = &port->dev;
>  	dev->bus = &cxl_bus_type;
>  
> +	/* Endpoints don't have a target list */
> +	if (nr_targets == 0)
> +		dev->type = &cxl_decoder_endpoint_type;
>  	/* root ports do not have a cxl_port_type parent */
> -	if (port->dev.parent->type == &cxl_port_type)
> +	else if (port->dev.parent->type == &cxl_port_type)
>  		dev->type = &cxl_decoder_switch_type;
>  	else
>  		dev->type = &cxl_decoder_root_type;
> @@ -579,12 +601,15 @@ int cxl_decoder_add(struct cxl_decoder *cxld, int *target_map)
>  	if (cxld->interleave_ways < 1)
>  		return -EINVAL;
>  
> -	port = to_cxl_port(cxld->dev.parent);
> -	rc = decoder_populate_targets(cxld, port, target_map);
> -	if (rc)
> -		return rc;
> -
>  	dev = &cxld->dev;
> +
> +	port = to_cxl_port(cxld->dev.parent);
> +	if (!is_endpoint_decoder(dev)) {
> +		rc = decoder_populate_targets(cxld, port, target_map);
> +		if (rc)
> +			return rc;
> +	}
> +
>  	rc = dev_set_name(dev, "decoder%d.%d", port->id, cxld->id);
>  	if (rc)
>  		return rc;
Ben Widawsky Nov. 22, 2021, 7:37 p.m. UTC | #2
On 21-11-22 16:20:39, Jonathan Cameron wrote:
> On Fri, 19 Nov 2021 16:02:39 -0800
> Ben Widawsky <ben.widawsky@intel.com> wrote:
> 
> > Endpoints have decoders too. It is useful to share the same
> > infrastructure from cxl_core. Endpoints do not have dports (downstream
> > targets), only the underlying physical medium. As a result, some special
> > casing is needed.
> > 
> > There is no functional change introduced yet as endpoints don't actually
> > enumerate decoders yet.
> > 
> > Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
> 
> I'm not a fan of special values like using 0 here to indicate endpoint
> device.  I'd rather see a base cxl_decode_alloc(..., bool ep)
> and possibly wrappers for the non ep case and ep one.
> 
> Jonathan
> 

My inclination is the opposite. However, I think you and Dan both brought up
something to this effect in the previous RFCs.

Dan, do you have a preference here?

> > ---
> >  drivers/cxl/core/bus.c | 41 +++++++++++++++++++++++++++++++++--------
> >  1 file changed, 33 insertions(+), 8 deletions(-)
> > 
> > diff --git a/drivers/cxl/core/bus.c b/drivers/cxl/core/bus.c
> > index 1ee12a60f3f4..16b15f54fb62 100644
> > --- a/drivers/cxl/core/bus.c
> > +++ b/drivers/cxl/core/bus.c
> > @@ -187,6 +187,12 @@ static const struct attribute_group *cxl_decoder_switch_attribute_groups[] = {
> >  	NULL,
> >  };
> >  
> > +static const struct attribute_group *cxl_decoder_endpoint_attribute_groups[] = {
> > +	&cxl_decoder_base_attribute_group,
> > +	&cxl_base_attribute_group,
> > +	NULL,
> > +};
> > +
> >  static void cxl_decoder_release(struct device *dev)
> >  {
> >  	struct cxl_decoder *cxld = to_cxl_decoder(dev);
> > @@ -196,6 +202,12 @@ static void cxl_decoder_release(struct device *dev)
> >  	kfree(cxld);
> >  }
> >  
> > +static const struct device_type cxl_decoder_endpoint_type = {
> > +	.name = "cxl_decoder_endpoint",
> > +	.release = cxl_decoder_release,
> > +	.groups = cxl_decoder_endpoint_attribute_groups,
> > +};
> > +
> >  static const struct device_type cxl_decoder_switch_type = {
> >  	.name = "cxl_decoder_switch",
> >  	.release = cxl_decoder_release,
> > @@ -208,6 +220,11 @@ static const struct device_type cxl_decoder_root_type = {
> >  	.groups = cxl_decoder_root_attribute_groups,
> >  };
> >  
> > +static bool is_endpoint_decoder(struct device *dev)
> > +{
> > +	return dev->type == &cxl_decoder_endpoint_type;
> > +}
> > +
> >  bool is_root_decoder(struct device *dev)
> >  {
> >  	return dev->type == &cxl_decoder_root_type;
> > @@ -499,7 +516,9 @@ static int decoder_populate_targets(struct cxl_decoder *cxld,
> >   * cxl_decoder_alloc - Allocate a new CXL decoder
> >   * @port: owning port of this decoder
> >   * @nr_targets: downstream targets accessible by this decoder. All upstream
> > - *		ports and root ports must have at least 1 target.
> > + *		ports and root ports must have at least 1 target. Endpoint
> > + *		devices will have 0 targets. Callers wishing to register an
> > + *		endpoint device should specify 0.
> >   *
> >   * A port should contain one or more decoders. Each of those decoders enable
> >   * some address space for CXL.mem utilization. A decoder is expected to be
> > @@ -516,7 +535,7 @@ struct cxl_decoder *cxl_decoder_alloc(struct cxl_port *port,
> >  	struct device *dev;
> >  	int rc = 0;
> >  
> > -	if (nr_targets > CXL_DECODER_MAX_INTERLEAVE || nr_targets == 0)
> > +	if (nr_targets > CXL_DECODER_MAX_INTERLEAVE)
> >  		return ERR_PTR(-EINVAL);
> >  
> >  	cxld = kzalloc(struct_size(cxld, target, nr_targets), GFP_KERNEL);
> > @@ -535,8 +554,11 @@ struct cxl_decoder *cxl_decoder_alloc(struct cxl_port *port,
> >  	dev->parent = &port->dev;
> >  	dev->bus = &cxl_bus_type;
> >  
> > +	/* Endpoints don't have a target list */
> > +	if (nr_targets == 0)
> > +		dev->type = &cxl_decoder_endpoint_type;
> >  	/* root ports do not have a cxl_port_type parent */
> > -	if (port->dev.parent->type == &cxl_port_type)
> > +	else if (port->dev.parent->type == &cxl_port_type)
> >  		dev->type = &cxl_decoder_switch_type;
> >  	else
> >  		dev->type = &cxl_decoder_root_type;
> > @@ -579,12 +601,15 @@ int cxl_decoder_add(struct cxl_decoder *cxld, int *target_map)
> >  	if (cxld->interleave_ways < 1)
> >  		return -EINVAL;
> >  
> > -	port = to_cxl_port(cxld->dev.parent);
> > -	rc = decoder_populate_targets(cxld, port, target_map);
> > -	if (rc)
> > -		return rc;
> > -
> >  	dev = &cxld->dev;
> > +
> > +	port = to_cxl_port(cxld->dev.parent);
> > +	if (!is_endpoint_decoder(dev)) {
> > +		rc = decoder_populate_targets(cxld, port, target_map);
> > +		if (rc)
> > +			return rc;
> > +	}
> > +
> >  	rc = dev_set_name(dev, "decoder%d.%d", port->id, cxld->id);
> >  	if (rc)
> >  		return rc;
>
Dan Williams Nov. 25, 2021, 12:07 a.m. UTC | #3
On Mon, Nov 22, 2021 at 11:38 AM Ben Widawsky <ben.widawsky@intel.com> wrote:
>
> On 21-11-22 16:20:39, Jonathan Cameron wrote:
> > On Fri, 19 Nov 2021 16:02:39 -0800
> > Ben Widawsky <ben.widawsky@intel.com> wrote:
> >
> > > Endpoints have decoders too. It is useful to share the same
> > > infrastructure from cxl_core. Endpoints do not have dports (downstream
> > > targets), only the underlying physical medium. As a result, some special
> > > casing is needed.
> > >
> > > There is no functional change introduced yet as endpoints don't actually
> > > enumerate decoders yet.
> > >
> > > Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
> >
> > I'm not a fan of special values like using 0 here to indicate endpoint
> > device.  I'd rather see a base cxl_decode_alloc(..., bool ep)
> > and possibly wrappers for the non ep case and ep one.
> >
> > Jonathan
> >
>
> My inclination is the opposite. However, I think you and Dan both brought up
> something to this effect in the previous RFCs.
>
> Dan, do you have a preference here?

I was thinking something along the lines of what Jonathan wants,
explicit per-type APIs, but internal / private to the core can use
heuristics like nr_targets == 0 == endpoint.

So unexport cxl_decoder_alloc() and have separate:

cxl_root_decoder_alloc()
cxl_switch_decoder_alloc()
cxl_endpoint_decoder_alloc()

...apis that use a static cxl_decoder_alloc() internally. Probably
also wants a cxl_endpoint_decoder_add() that drops the need to pass a
NULL @target_map.
Ben Widawsky Nov. 29, 2021, 8:05 p.m. UTC | #4
On 21-11-24 16:07:23, Dan Williams wrote:
> On Mon, Nov 22, 2021 at 11:38 AM Ben Widawsky <ben.widawsky@intel.com> wrote:
> >
> > On 21-11-22 16:20:39, Jonathan Cameron wrote:
> > > On Fri, 19 Nov 2021 16:02:39 -0800
> > > Ben Widawsky <ben.widawsky@intel.com> wrote:
> > >
> > > > Endpoints have decoders too. It is useful to share the same
> > > > infrastructure from cxl_core. Endpoints do not have dports (downstream
> > > > targets), only the underlying physical medium. As a result, some special
> > > > casing is needed.
> > > >
> > > > There is no functional change introduced yet as endpoints don't actually
> > > > enumerate decoders yet.
> > > >
> > > > Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
> > >
> > > I'm not a fan of special values like using 0 here to indicate endpoint
> > > device.  I'd rather see a base cxl_decode_alloc(..., bool ep)
> > > and possibly wrappers for the non ep case and ep one.
> > >
> > > Jonathan
> > >
> >
> > My inclination is the opposite. However, I think you and Dan both brought up
> > something to this effect in the previous RFCs.
> >
> > Dan, do you have a preference here?
> 
> I was thinking something along the lines of what Jonathan wants,
> explicit per-type APIs, but internal / private to the core can use
> heuristics like nr_targets == 0 == endpoint.
> 
> So unexport cxl_decoder_alloc() and have separate:
> 
> cxl_root_decoder_alloc()
> cxl_switch_decoder_alloc()
> cxl_endpoint_decoder_alloc()
> 
> ...apis that use a static cxl_decoder_alloc() internally. Probably
> also wants a cxl_endpoint_decoder_add() that drops the need to pass a
> NULL @target_map.

Would you a like a prep patch to set up the APIs first, or just do it all in
one?
Dan Williams Nov. 29, 2021, 8:07 p.m. UTC | #5
On Mon, Nov 29, 2021 at 12:05 PM Ben Widawsky <ben.widawsky@intel.com> wrote:
>
> On 21-11-24 16:07:23, Dan Williams wrote:
> > On Mon, Nov 22, 2021 at 11:38 AM Ben Widawsky <ben.widawsky@intel.com> wrote:
> > >
> > > On 21-11-22 16:20:39, Jonathan Cameron wrote:
> > > > On Fri, 19 Nov 2021 16:02:39 -0800
> > > > Ben Widawsky <ben.widawsky@intel.com> wrote:
> > > >
> > > > > Endpoints have decoders too. It is useful to share the same
> > > > > infrastructure from cxl_core. Endpoints do not have dports (downstream
> > > > > targets), only the underlying physical medium. As a result, some special
> > > > > casing is needed.
> > > > >
> > > > > There is no functional change introduced yet as endpoints don't actually
> > > > > enumerate decoders yet.
> > > > >
> > > > > Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
> > > >
> > > > I'm not a fan of special values like using 0 here to indicate endpoint
> > > > device.  I'd rather see a base cxl_decode_alloc(..., bool ep)
> > > > and possibly wrappers for the non ep case and ep one.
> > > >
> > > > Jonathan
> > > >
> > >
> > > My inclination is the opposite. However, I think you and Dan both brought up
> > > something to this effect in the previous RFCs.
> > >
> > > Dan, do you have a preference here?
> >
> > I was thinking something along the lines of what Jonathan wants,
> > explicit per-type APIs, but internal / private to the core can use
> > heuristics like nr_targets == 0 == endpoint.
> >
> > So unexport cxl_decoder_alloc() and have separate:
> >
> > cxl_root_decoder_alloc()
> > cxl_switch_decoder_alloc()
> > cxl_endpoint_decoder_alloc()
> >
> > ...apis that use a static cxl_decoder_alloc() internally. Probably
> > also wants a cxl_endpoint_decoder_add() that drops the need to pass a
> > NULL @target_map.
>
> Would you a like a prep patch to set up the APIs first, or just do it all in
> one?

Prep patch to switch over the current usages to the new style before
introducing more helpers sounds good to me.
Ben Widawsky Nov. 29, 2021, 8:12 p.m. UTC | #6
On 21-11-29 12:07:00, Dan Williams wrote:
> On Mon, Nov 29, 2021 at 12:05 PM Ben Widawsky <ben.widawsky@intel.com> wrote:
> >
> > On 21-11-24 16:07:23, Dan Williams wrote:
> > > On Mon, Nov 22, 2021 at 11:38 AM Ben Widawsky <ben.widawsky@intel.com> wrote:
> > > >
> > > > On 21-11-22 16:20:39, Jonathan Cameron wrote:
> > > > > On Fri, 19 Nov 2021 16:02:39 -0800
> > > > > Ben Widawsky <ben.widawsky@intel.com> wrote:
> > > > >
> > > > > > Endpoints have decoders too. It is useful to share the same
> > > > > > infrastructure from cxl_core. Endpoints do not have dports (downstream
> > > > > > targets), only the underlying physical medium. As a result, some special
> > > > > > casing is needed.
> > > > > >
> > > > > > There is no functional change introduced yet as endpoints don't actually
> > > > > > enumerate decoders yet.
> > > > > >
> > > > > > Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
> > > > >
> > > > > I'm not a fan of special values like using 0 here to indicate endpoint
> > > > > device.  I'd rather see a base cxl_decode_alloc(..., bool ep)
> > > > > and possibly wrappers for the non ep case and ep one.
> > > > >
> > > > > Jonathan
> > > > >
> > > >
> > > > My inclination is the opposite. However, I think you and Dan both brought up
> > > > something to this effect in the previous RFCs.
> > > >
> > > > Dan, do you have a preference here?
> > >
> > > I was thinking something along the lines of what Jonathan wants,
> > > explicit per-type APIs, but internal / private to the core can use
> > > heuristics like nr_targets == 0 == endpoint.
> > >
> > > So unexport cxl_decoder_alloc() and have separate:
> > >
> > > cxl_root_decoder_alloc()
> > > cxl_switch_decoder_alloc()
> > > cxl_endpoint_decoder_alloc()
> > >
> > > ...apis that use a static cxl_decoder_alloc() internally. Probably
> > > also wants a cxl_endpoint_decoder_add() that drops the need to pass a
> > > NULL @target_map.
> >
> > Would you a like a prep patch to set up the APIs first, or just do it all in
> > one?
> 
> Prep patch to switch over the current usages to the new style before
> introducing more helpers sounds good to me.

Thanks for the suggestions... Looking again, I think it makes sense to squash it
into the patch before this which documents and tightens up this exact API.
diff mbox series

Patch

diff --git a/drivers/cxl/core/bus.c b/drivers/cxl/core/bus.c
index 1ee12a60f3f4..16b15f54fb62 100644
--- a/drivers/cxl/core/bus.c
+++ b/drivers/cxl/core/bus.c
@@ -187,6 +187,12 @@  static const struct attribute_group *cxl_decoder_switch_attribute_groups[] = {
 	NULL,
 };
 
+static const struct attribute_group *cxl_decoder_endpoint_attribute_groups[] = {
+	&cxl_decoder_base_attribute_group,
+	&cxl_base_attribute_group,
+	NULL,
+};
+
 static void cxl_decoder_release(struct device *dev)
 {
 	struct cxl_decoder *cxld = to_cxl_decoder(dev);
@@ -196,6 +202,12 @@  static void cxl_decoder_release(struct device *dev)
 	kfree(cxld);
 }
 
+static const struct device_type cxl_decoder_endpoint_type = {
+	.name = "cxl_decoder_endpoint",
+	.release = cxl_decoder_release,
+	.groups = cxl_decoder_endpoint_attribute_groups,
+};
+
 static const struct device_type cxl_decoder_switch_type = {
 	.name = "cxl_decoder_switch",
 	.release = cxl_decoder_release,
@@ -208,6 +220,11 @@  static const struct device_type cxl_decoder_root_type = {
 	.groups = cxl_decoder_root_attribute_groups,
 };
 
+static bool is_endpoint_decoder(struct device *dev)
+{
+	return dev->type == &cxl_decoder_endpoint_type;
+}
+
 bool is_root_decoder(struct device *dev)
 {
 	return dev->type == &cxl_decoder_root_type;
@@ -499,7 +516,9 @@  static int decoder_populate_targets(struct cxl_decoder *cxld,
  * cxl_decoder_alloc - Allocate a new CXL decoder
  * @port: owning port of this decoder
  * @nr_targets: downstream targets accessible by this decoder. All upstream
- *		ports and root ports must have at least 1 target.
+ *		ports and root ports must have at least 1 target. Endpoint
+ *		devices will have 0 targets. Callers wishing to register an
+ *		endpoint device should specify 0.
  *
  * A port should contain one or more decoders. Each of those decoders enable
  * some address space for CXL.mem utilization. A decoder is expected to be
@@ -516,7 +535,7 @@  struct cxl_decoder *cxl_decoder_alloc(struct cxl_port *port,
 	struct device *dev;
 	int rc = 0;
 
-	if (nr_targets > CXL_DECODER_MAX_INTERLEAVE || nr_targets == 0)
+	if (nr_targets > CXL_DECODER_MAX_INTERLEAVE)
 		return ERR_PTR(-EINVAL);
 
 	cxld = kzalloc(struct_size(cxld, target, nr_targets), GFP_KERNEL);
@@ -535,8 +554,11 @@  struct cxl_decoder *cxl_decoder_alloc(struct cxl_port *port,
 	dev->parent = &port->dev;
 	dev->bus = &cxl_bus_type;
 
+	/* Endpoints don't have a target list */
+	if (nr_targets == 0)
+		dev->type = &cxl_decoder_endpoint_type;
 	/* root ports do not have a cxl_port_type parent */
-	if (port->dev.parent->type == &cxl_port_type)
+	else if (port->dev.parent->type == &cxl_port_type)
 		dev->type = &cxl_decoder_switch_type;
 	else
 		dev->type = &cxl_decoder_root_type;
@@ -579,12 +601,15 @@  int cxl_decoder_add(struct cxl_decoder *cxld, int *target_map)
 	if (cxld->interleave_ways < 1)
 		return -EINVAL;
 
-	port = to_cxl_port(cxld->dev.parent);
-	rc = decoder_populate_targets(cxld, port, target_map);
-	if (rc)
-		return rc;
-
 	dev = &cxld->dev;
+
+	port = to_cxl_port(cxld->dev.parent);
+	if (!is_endpoint_decoder(dev)) {
+		rc = decoder_populate_targets(cxld, port, target_map);
+		if (rc)
+			return rc;
+	}
+
 	rc = dev_set_name(dev, "decoder%d.%d", port->id, cxld->id);
 	if (rc)
 		return rc;