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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 >>> Co-developed-by: Anil S Keshavamurthy >>> Signed-off-by: Anil S Keshavamurthy >>> >>> 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/dsacap >>> +Date: June 1, 2025 >>> +KernelVersion: 6.17.0 >>> +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 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/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); >>> + >> The dsacaps are invalid for DSA 1 and 2. Not safe to read and assign the >> bits on DSA 1 and 2. >> >> Better to assign the dsacap bits only when idxd.hw.version >= DSA_VERSION_3. > The registers are architecturally guaranteed to return 0 on prior versions, so it is > safe to read them on DSA 1 and 2 and there is no need for an additional check. Although it's safe to read them here on DSA 1 and 2, reading a reserved value generally is not a good code practice in the kernel. I would still suggest to avoid to read the reserved values on DSA 1 and 2. Thanks. -Fenghua