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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. My previous understanding was that ioread64() would ensure safe behavior on DSA1.0 and DSA2.0. However, I'm fine with Fenghua's suggestion adding the condition version >= DSA_VERSION_3. It can provide future-proofing in case the behavior of ioread64() changes. Thanks --Sun, Yi