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Message-ID: <50e151ed-af26-49f6-86c8-ebb7b1ad43ca@intel.com>
Date: Fri, 13 Jun 2025 13:59:25 -0700
From: Dave Jiang <dave.jiang@...el.com>
To: Yi Sun <yi.sun@...el.com>, vinicius.gomes@...el.com,
dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: gordon.jin@...el.com, fenghuay@...dia.com,
anil.s.keshavamurthy@...el.com, philip.lantz@...el.com
Subject: Re: [PATCH 1/2] dmaengine: idxd: Expose DSA3.0 capabilities through
sysfs
On 6/13/25 9:18 AM, Yi Sun wrote:
> 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 consists of values from the three dsacap registers, concatenated
> in order and separated by commas.
>
> Example:
> cat /sys/bus/dsa/devices/dsa0/dsacap
> 0014000e000007aa,00fa01ff01ff03ff,000000000000f18d
>
> Signed-off-by: Yi Sun <yi.sun@...el.com>
> Co-developed-by: Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>
> Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>
Would be good to provide a link to the 3.0 spec. Otherwise
Reviewed-by: Dave Jiang <dave.jiang@...el.com>
>
> diff --git a/Documentation/ABI/stable/sysfs-driver-dma-idxd b/Documentation/ABI/stable/sysfs-driver-dma-idxd
> index 4a355e6747ae..f9568ea52b2f 100644
> --- a/Documentation/ABI/stable/sysfs-driver-dma-idxd
> +++ b/Documentation/ABI/stable/sysfs-driver-dma-idxd
> @@ -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>/dsacap
> +Date: June 1, 2025
> +KernelVersion: 6.17.0
> +Contact: dmaengine@...r.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 consists of values from the three dsacap registers,
> + concatenated in order and separated by commas.
> + 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
> diff --git a/drivers/dma/idxd/idxd.h b/drivers/dma/idxd/idxd.h
> index 74e6695881e6..cc0a3fe1c957 100644
> --- a/drivers/dma/idxd/idxd.h
> +++ b/drivers/dma/idxd/idxd.h
> @@ -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 {
> diff --git a/drivers/dma/idxd/init.c b/drivers/dma/idxd/init.c
> index 80355d03004d..cc8203320d40 100644
> --- a/drivers/dma/idxd/init.c
> +++ b/drivers/dma/idxd/init.c
> @@ -582,6 +582,10 @@ static void idxd_read_caps(struct idxd_device *idxd)
> }
> multi_u64_to_bmap(idxd->opcap_bmap, &idxd->hw.opcap.bits[0], 4);
>
> + 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);
> diff --git a/drivers/dma/idxd/registers.h b/drivers/dma/idxd/registers.h
> index 006ba206ab1b..45485ecd7bb6 100644
> --- a/drivers/dma/idxd/registers.h
> +++ b/drivers/dma/idxd/registers.h
> @@ -13,6 +13,7 @@
>
> #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
> @@ -582,6 +583,21 @@ union evl_status_reg {
> u64 bits;
> } __packed;
>
> +#define IDXD_DSACAP0_OFFSET 0x180
> +union dsacap0_reg {
> + u64 bits;
> +};
> +
> +#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 {
> diff --git a/drivers/dma/idxd/sysfs.c b/drivers/dma/idxd/sysfs.c
> index 9f0701021af0..624b7d1b193f 100644
> --- a/drivers/dma/idxd/sysfs.c
> +++ b/drivers/dma/idxd/sysfs.c
> @@ -1713,6 +1713,21 @@ static ssize_t event_log_size_store(struct device *dev,
> }
> static DEVICE_ATTR_RW(event_log_size);
>
> +static ssize_t dsacap_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct idxd_device *idxd = confdev_to_idxd(dev);
> +
> + return sysfs_emit(buf, "%08x,%08x,%08x,%08x,%08x,%08x\n",
> + upper_32_bits(idxd->hw.dsacap0.bits),
> + lower_32_bits(idxd->hw.dsacap0.bits),
> + upper_32_bits(idxd->hw.dsacap1.bits),
> + lower_32_bits(idxd->hw.dsacap1.bits),
> + upper_32_bits(idxd->hw.dsacap2.bits),
> + lower_32_bits(idxd->hw.dsacap2.bits));
> +}
> +static DEVICE_ATTR_RO(dsacap);
> +
> static bool idxd_device_attr_max_batch_size_invisible(struct attribute *attr,
> struct idxd_device *idxd)
> {
> @@ -1750,6 +1765,14 @@ static bool idxd_device_attr_event_log_size_invisible(struct attribute *attr,
> !idxd->hw.gen_cap.evl_support);
> }
>
> +static bool idxd_device_attr_dsacap_invisible(struct attribute *attr,
> + struct idxd_device *idxd)
> +{
> + return attr == &dev_attr_dsacap.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 +1791,9 @@ 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_dsacap_invisible(attr, idxd))
> + return 0;
> +
> return attr->mode;
> }
>
> @@ -1795,6 +1821,7 @@ static struct attribute *idxd_device_attributes[] = {
> &dev_attr_cmd_status.attr,
> &dev_attr_iaa_cap.attr,
> &dev_attr_event_log_size.attr,
> + &dev_attr_dsacap.attr,
> NULL,
> };
>
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