[PATCH v4 14/25] dmaengine: sdxi: Add unit tests for descriptor ring reservations

From: Nathan Lynch via B4 Relay

Date: Tue Nov 03 2026 - 21:52:38 EST

From: Nathan Lynch <nathan.lynch@xxxxxxx>

Add hardware-independent KUnit tests for full-ring and single-slot
reservations, invalid counts, inconsistent indices, insufficient space,
and bounded reservations and descriptor access after ring wrap.

Include the SDXI KUnit configuration and test build support. Run with:

tools/testing/kunit/kunit.py run \
--kunitconfig=drivers/dma/sdxi/.kunitconfig

Co-developed-by: Wei Huang <wei.huang2@xxxxxxx>
Signed-off-by: Wei Huang <wei.huang2@xxxxxxx>
Signed-off-by: Nathan Lynch <nathan.lynch@xxxxxxx>
---
drivers/dma/sdxi/.kunitconfig | 4 ++
drivers/dma/sdxi/Kconfig | 10 +++
drivers/dma/sdxi/Makefile | 3 +
drivers/dma/sdxi/ring_kunit.c | 147 ++++++++++++++++++++++++++++++++++++++++++
4 files changed, 164 insertions(+)

diff --git a/drivers/dma/sdxi/.kunitconfig b/drivers/dma/sdxi/.kunitconfig
new file mode 100644
index 000000000000..16a1ae04b156
--- /dev/null
+++ b/drivers/dma/sdxi/.kunitconfig
@@ -0,0 +1,4 @@
+CONFIG_KUNIT=y
+CONFIG_DMADEVICES=y
+CONFIG_SDXI_CORE=y
+CONFIG_SDXI_KUNIT_TEST=y
diff --git a/drivers/dma/sdxi/Kconfig b/drivers/dma/sdxi/Kconfig
index b91b44231a04..7217375c9216 100644
--- a/drivers/dma/sdxi/Kconfig
+++ b/drivers/dma/sdxi/Kconfig
@@ -26,3 +26,13 @@ config SDXI_PCI

To compile this driver as a module, choose M here: the module
will be named "sdxi-pci".
+
+config SDXI_KUNIT_TEST
+ tristate "SDXI unit tests" if !KUNIT_ALL_TESTS
+ depends on SDXI_CORE && KUNIT
+ default KUNIT_ALL_TESTS
+ help
+ KUnit tests for parts of the SDXI driver. Does not require
+ SDXI hardware.
+
+ If unsure, say N.
diff --git a/drivers/dma/sdxi/Makefile b/drivers/dma/sdxi/Makefile
index bfcb443f1e64..00e3f1cb0808 100644
--- a/drivers/dma/sdxi/Makefile
+++ b/drivers/dma/sdxi/Makefile
@@ -7,3 +7,6 @@ sdxi-core-y := \

obj-$(CONFIG_SDXI_PCI) += sdxi-pci.o
sdxi-pci-y := pci.o
+
+obj-$(CONFIG_SDXI_KUNIT_TEST) += \
+ ring_kunit.o
diff --git a/drivers/dma/sdxi/ring_kunit.c b/drivers/dma/sdxi/ring_kunit.c
new file mode 100644
index 000000000000..7df85fc5549c
--- /dev/null
+++ b/drivers/dma/sdxi/ring_kunit.c
@@ -0,0 +1,147 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * SDXI descriptor ring management tests.
+ *
+ * Copyright Advanced Micro Devices, Inc.
+ */
+#include <kunit/device.h>
+#include <kunit/test-bug.h>
+#include <kunit/test.h>
+#include <linux/container_of.h>
+#include <linux/dma-mapping.h>
+#include <linux/module.h>
+#include <linux/overflow.h>
+#include <linux/packing.h>
+#include <linux/string.h>
+
+#include "ring.h"
+#include "submission.h"
+
+MODULE_IMPORT_NS("EXPORTED_FOR_KUNIT_TESTING");
+
+/* A submission queue backed by plain memory; no device or DMA required. */
+static struct sdxi_sq *alloc_sq(struct kunit *t, u32 count)
+{
+ struct sdxi_sq *sq;
+
+ sq = kunit_kmalloc(t, struct_size(sq, ring, count),
+ GFP_KERNEL | __GFP_ZERO);
+ if (sq)
+ sq->count = count;
+ return sq;
+}
+
+static void valid(struct kunit *t)
+{
+ struct sdxi_ring_state r;
+ struct sdxi_ring_resv resv;
+ struct sdxi_sq *sq;
+
+ sq = alloc_sq(t, SZ_1K);
+ KUNIT_ASSERT_NOT_NULL(t, sq);
+
+ sdxi_ring_state_init(&r, sq);
+
+ KUNIT_EXPECT_EQ(t, sdxi_ring_try_reserve(&r, sq->count, &resv), 0);
+ KUNIT_EXPECT_EQ(t, resv.range.start, 0);
+ KUNIT_EXPECT_EQ(t, resv.range.end, sq->count - 1);
+ KUNIT_EXPECT_EQ(t, sdxi_ring_resv_count(&resv), sq->count);
+ KUNIT_EXPECT_EQ(t, le64_to_cpu(sq->write_index), sq->count);
+
+ /* A ring-sized reservation maps slot i onto ring entry i. */
+ for (unsigned int i = 0; i < sq->count; i++) {
+ KUNIT_EXPECT_EQ(t, sdxi_ring_resv_index(&resv, i), i);
+ KUNIT_EXPECT_PTR_EQ(t, sdxi_ring_desc(&r, i), &sq->ring[i]);
+ }
+
+ sq->cxt_sts.read_index = cpu_to_le64(1);
+ KUNIT_EXPECT_EQ(t, sdxi_ring_try_reserve(&r, 1, &resv), 0);
+ KUNIT_EXPECT_EQ(t, le64_to_cpu(sq->write_index), sq->count + 1);
+ KUNIT_EXPECT_EQ(t, sdxi_ring_resv_count(&resv), 1);
+
+ /* The index space is unwrapped: index sq->count is entry 0. */
+ KUNIT_EXPECT_EQ(t, sdxi_ring_resv_index(&resv, 0), sq->count);
+ KUNIT_EXPECT_PTR_EQ(t, sdxi_ring_desc(&r, sq->count), &sq->ring[0]);
+}
+
+static void invalid(struct kunit *t)
+{
+ struct sdxi_ring_state rs;
+ struct sdxi_ring_resv resv;
+ struct sdxi_sq *sq;
+
+ sq = alloc_sq(t, SZ_1K);
+ KUNIT_ASSERT_NOT_NULL(t, sq);
+
+ sdxi_ring_state_init(&rs, sq);
+
+ KUNIT_EXPECT_EQ(t, sdxi_ring_try_reserve(&rs, 0, &resv), -EINVAL);
+ KUNIT_EXPECT_EQ(t, sdxi_ring_try_reserve(&rs, sq->count + 1, &resv), -EINVAL);
+
+ sq->cxt_sts.read_index = cpu_to_le64(1);
+ KUNIT_EXPECT_EQ(t, sdxi_ring_try_reserve(&rs, 1, &resv), -EIO);
+
+ sq->cxt_sts.read_index = 0;
+ sq->write_index = cpu_to_le64(sq->count);
+ sdxi_ring_state_init(&rs, sq);
+ KUNIT_EXPECT_EQ(t, sdxi_ring_try_reserve(&rs, 1, &resv), -EBUSY);
+
+ sq->cxt_sts.read_index = cpu_to_le64(sq->count);
+ sq->write_index = cpu_to_le64(sq->count + 1);
+ sdxi_ring_state_init(&rs, sq);
+ KUNIT_EXPECT_EQ(t, sdxi_ring_try_reserve(&rs, sq->count, &resv), -EBUSY);
+}
+
+static void bounded_reservations(struct kunit *t)
+{
+ struct sdxi_ring_state rs;
+ struct sdxi_ring_resv resv;
+ struct sdxi_sq *sq = alloc_sq(t, SZ_1K);
+
+ KUNIT_ASSERT_NOT_NULL(t, sq);
+ sdxi_ring_state_init(&rs, sq);
+ KUNIT_EXPECT_EQ(t, sdxi_ring_try_reserve_range(&rs, 0, 2, &resv), -EINVAL);
+ KUNIT_EXPECT_EQ(t, sdxi_ring_try_reserve_range(&rs, 3, 2, &resv), -EINVAL);
+ KUNIT_EXPECT_EQ(t, sdxi_ring_try_reserve_range(&rs, 2, sq->count + 1, &resv),
+ -EINVAL);
+
+ sq->write_index = cpu_to_le64(sq->count - 2);
+ KUNIT_ASSERT_EQ(t, sdxi_ring_try_reserve_range(&rs, 2, 10, &resv), 0);
+ KUNIT_EXPECT_EQ(t, sdxi_ring_resv_count(&resv), 2);
+ KUNIT_EXPECT_EQ(t, resv.range.start, sq->count - 2);
+ KUNIT_EXPECT_EQ(t, sdxi_ring_try_reserve_range(&rs, 2, 10, &resv), -EBUSY);
+ sq->cxt_sts.read_index = cpu_to_le64(1);
+ KUNIT_EXPECT_EQ(t, sdxi_ring_try_reserve_range(&rs, 2, 10, &resv), -EBUSY);
+ sq->cxt_sts.read_index = cpu_to_le64(5);
+ KUNIT_ASSERT_EQ(t, sdxi_ring_try_reserve_range(&rs, 2, 10, &resv), 0);
+ KUNIT_EXPECT_EQ(t, sdxi_ring_resv_count(&resv), 5);
+ KUNIT_EXPECT_PTR_EQ(t, sdxi_slot_desc(sdxi_ring_resv_slot(&resv, 0)),
+ &sq->ring[0]);
+}
+
+static struct kunit_case testcases[] = {
+ KUNIT_CASE(valid),
+ KUNIT_CASE(invalid),
+ KUNIT_CASE(bounded_reservations),
+ {}
+};
+
+static int setup_device(struct kunit *t)
+{
+ struct device *dev = kunit_device_register(t, "sdxi-mock-device");
+
+ KUNIT_ASSERT_NOT_ERR_OR_NULL(t, dev);
+ t->priv = dev;
+ return 0;
+}
+
+static struct kunit_suite generic_desc_ts = {
+ .name = "SDXI descriptor ring management",
+ .test_cases = testcases,
+ .init = setup_device,
+};
+kunit_test_suite(generic_desc_ts);
+
+MODULE_DESCRIPTION("SDXI descriptor ring tests");
+MODULE_AUTHOR("Nathan Lynch");
+MODULE_LICENSE("GPL");

--
2.56.0