Commit 8308510b authored by Yi Sun's avatar Yi Sun Committed by Vinod Koul
Browse files

dmaengine: idxd: Expose DSA3.0 capabilities through sysfs 

Introduce sysfs interfaces for 3 new Data Streaming Accelerator (DSA)
capability registers (dsacap0-2) to enable userspace awareness of hardware
features in DSA version 3 and later devices.

Userspace components (e.g. configure libraries, workload Apps) require this
information to:
1. Select optimal data transfer strategies based on SGL capabilities
2. Enable hardware-specific optimizations for floating-point operations
3. Configure memory operations with proper numerical handling
4. Verify compute operation compatibility before submitting jobs

The output format is <dsacap2>,<dsacap1>,<dsacap0>, where each DSA
capability value is a 64-bit hexadecimal number, separated by commas.
The ordering follows the DSA 3.0 specification layout:
 Offset:    0x190    0x188    0x180
 Reg:       dsacap2  dsacap1  dsacap0

Example:
cat /sys/bus/dsa/devices/dsa0/dsacaps
 000000000000f18d,0014000e000007aa,00fa01ff01ff03ff

According to the DSA 3.0 specification, there are 15 fields defined for
the three dsacap registers. However, there's no need to define all
register structures unless a use case requires them. At this point,
support for the Scatter-Gather List (SGL) located in dsacap0 is necessary,
so only dsacap0 is defined accordingly.

For reference, the DSA 3.0 specification is available at:
Link: https://software.intel.com/content/www/us/en/develop/articles/intel-data-streaming-accelerator-architecture-specification.html



Signed-off-by: default avatarYi Sun <yi.sun@intel.com>
Co-developed-by: default avatarAnil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: default avatarAnil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Reviewed-by: default avatarDave Jiang <dave.jiang@intel.com>
Tested-by: default avatarYi Lai <yi1.lai@intel.com>
Acked-by: default avatarVinicius Costa Gomes <vinicius.gomes@intel.com>
Link: https://patch.msgid.link/20260107-idxd-yi-sun-dsa3-sgl-size-v2-1-dbef8f559e48@intel.com


Signed-off-by: default avatarVinod Koul <vkoul@kernel.org>
parent e0c51fd0

Documentation/ABI/stable/sysfs-driver-dma-idxd

+15 −0
Original line number Diff line number Diff line
@@ -136,6 +136,21 @@ Description: The last executed device administrative command's status/error. 
		Also last configuration error overloaded.

		Writing to it will clear the status.



What:		/sys/bus/dsa/devices/dsa<m>/dsacaps

Date:		April 5, 2026

KernelVersion:	6.20.0

Contact:	dmaengine@vger.kernel.org

Description:	The DSA3 specification introduces three new capability

		registers: dsacap[0-2]. User components (e.g., configuration

		libraries and workload applications) require this information

		to properly utilize the DSA3 features.

		This includes SGL capability support, Enabling hardware-specific

		optimizations, Configuring memory, etc.

		The output format is '<dsacap2>,<dsacap1>,<dsacap0>' where each

		DSA cap value is a 64 bit hex value.

		This attribute should only be visible on DSA devices of version

		3 or later.



What:		/sys/bus/dsa/devices/dsa<m>/iaa_cap

Date:		Sept 14, 2022

KernelVersion: 6.0.0

drivers/dma/idxd/idxd.h

+3 −0
Original line number Diff line number Diff line
@@ -252,6 +252,9 @@ struct idxd_hw { 
	struct opcap opcap;

	u32 cmd_cap;

	union iaa_cap_reg iaa_cap;

	union dsacap0_reg dsacap0;

	union dsacap1_reg dsacap1;

	union dsacap2_reg dsacap2;

};



enum idxd_device_state {

drivers/dma/idxd/init.c

+6 −0
Original line number Diff line number Diff line
@@ -585,6 +585,12 @@ static void idxd_read_caps(struct idxd_device *idxd) 
	}

	multi_u64_to_bmap(idxd->opcap_bmap, &idxd->hw.opcap.bits[0], 4);



	if (idxd->hw.version >= DEVICE_VERSION_3) {

		idxd->hw.dsacap0.bits = ioread64(idxd->reg_base + IDXD_DSACAP0_OFFSET);

		idxd->hw.dsacap1.bits = ioread64(idxd->reg_base + IDXD_DSACAP1_OFFSET);

		idxd->hw.dsacap2.bits = ioread64(idxd->reg_base + IDXD_DSACAP2_OFFSET);

	}



	/* read iaa cap */

	if (idxd->data->type == IDXD_TYPE_IAX && idxd->hw.version >= DEVICE_VERSION_2)

		idxd->hw.iaa_cap.bits = ioread64(idxd->reg_base + IDXD_IAACAP_OFFSET);

drivers/dma/idxd/registers.h

+25 −0
Original line number Diff line number Diff line
@@ -18,6 +18,7 @@ 


#define DEVICE_VERSION_1		0x100

#define DEVICE_VERSION_2		0x200

#define DEVICE_VERSION_3		0x300



#define IDXD_MMIO_BAR		0

#define IDXD_WQ_BAR		2
@@ -587,6 +588,30 @@ union evl_status_reg { 
	u64 bits;

};



#define IDXD_DSACAP0_OFFSET		0x180

union dsacap0_reg {

	u64 bits;

	struct {

		u64 max_sgl_shift:4;

		u64 max_gr_block_shift:4;

		u64 ops_inter_domain:7;

		u64 rsvd1:17;

		u64 sgl_formats:16;

		u64 max_sg_process:8;

		u64 rsvd2:8;

	};

};



#define IDXD_DSACAP1_OFFSET		0x188

union dsacap1_reg {

	u64 bits;

};



#define IDXD_DSACAP2_OFFSET		0x190

union dsacap2_reg {

	u64 bits;

};



#define IDXD_MAX_BATCH_IDENT	256



struct __evl_entry {

drivers/dma/idxd/sysfs.c

+24 −0
Original line number Diff line number Diff line
@@ -1713,6 +1713,18 @@ static ssize_t event_log_size_store(struct device *dev, 
}

static DEVICE_ATTR_RW(event_log_size);



static ssize_t dsacaps_show(struct device *dev,

			    struct device_attribute *attr, char *buf)

{

	struct idxd_device *idxd = confdev_to_idxd(dev);



	return sysfs_emit(buf, "%016llx,%016llx,%016llx\n",

			  (u64)idxd->hw.dsacap2.bits,

			  (u64)idxd->hw.dsacap1.bits,

			  (u64)idxd->hw.dsacap0.bits);

}

static DEVICE_ATTR_RO(dsacaps);



static bool idxd_device_attr_max_batch_size_invisible(struct attribute *attr,

						      struct idxd_device *idxd)

{
@@ -1750,6 +1762,14 @@ static bool idxd_device_attr_event_log_size_invisible(struct attribute *attr, 
		!idxd->hw.gen_cap.evl_support);

}



static bool idxd_device_attr_dsacaps_invisible(struct attribute *attr,

					       struct idxd_device *idxd)

{

	return attr == &dev_attr_dsacaps.attr &&

		(idxd->data->type != IDXD_TYPE_DSA ||

		idxd->hw.version < DEVICE_VERSION_3);

}



static umode_t idxd_device_attr_visible(struct kobject *kobj,

					struct attribute *attr, int n)

{
@@ -1768,6 +1788,9 @@ static umode_t idxd_device_attr_visible(struct kobject *kobj, 
	if (idxd_device_attr_event_log_size_invisible(attr, idxd))

		return 0;



	if (idxd_device_attr_dsacaps_invisible(attr, idxd))

		return 0;



	return attr->mode;

}
@@ -1795,6 +1818,7 @@ static struct attribute *idxd_device_attributes[] = { 
	&dev_attr_cmd_status.attr,

	&dev_attr_iaa_cap.attr,

	&dev_attr_event_log_size.attr,

	&dev_attr_dsacaps.attr,

	NULL,

};