[PATCH v2 4/4] spi: Add KUnit coverage for DMA mapping error paths

Add KUnit tests for the __spi_map_msg() error paths. The tests verify
that a later TX or RX mapping failure clears the mapping state of
earlier transfers and leaves cur_{tx,rx}_dma_dev identifying the
current mapping device.

A zero-length transfer causes sg_alloc_table() to return -EINVAL,
providing deterministic failure injection without test hooks.
Additional cases cover successful map/unmap and a message which
requires no mapping.

Build the DMA suite as a separate translation unit, exposing the two
internal mapping helpers only for KUnit through the local internal
header. Enable SPI in the default and all-tests KUnit configurations so
the suite is exercised there.

Signed-off-by: Honghui Jiang <[email protected]>
---
 drivers/spi/.kunitconfig                     |   4 +
 drivers/spi/Kconfig                          |  13 +
 drivers/spi/Makefile                         |   1 +
 drivers/spi/internals.h                      |   9 +-
 drivers/spi/spi.c                            |   9 +-
 drivers/spi/tests/Makefile                   |   3 +
 drivers/spi/tests/spi-dma-kunit.c            | 259 +++++++++++++++++++
 tools/testing/kunit/configs/all_tests.config |   1 +
 tools/testing/kunit/configs/default.config   |   1 +
 9 files changed, 296 insertions(+), 4 deletions(-)
 create mode 100644 drivers/spi/.kunitconfig
 create mode 100644 drivers/spi/tests/Makefile
 create mode 100644 drivers/spi/tests/spi-dma-kunit.c

diff --git a/drivers/spi/.kunitconfig b/drivers/spi/.kunitconfig
new file mode 100644
index 000000000..07fa092c8
--- /dev/null
+++ b/drivers/spi/.kunitconfig
@@ -0,0 +1,4 @@
+CONFIG_KUNIT=y
+CONFIG_SPI=y
+CONFIG_SPI_MASTER=y
+CONFIG_SPI_DMA_KUNIT_TEST=y
diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index 8782514bb..74382c31e 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -1360,6 +1360,19 @@ config SPI_SPIDEV
 	help
 	  This supports user mode SPI protocol drivers.
 
+config SPI_DMA_KUNIT_TEST
+	tristate "KUnit tests for SPI core DMA mapping" if !KUNIT_ALL_TESTS
+	depends on KUNIT && HAS_DMA
+	default KUNIT_ALL_TESTS
+	help
+	  Build KUnit tests for SPI core DMA mapping. The tests exercise
+	  partial TX and RX mapping failures, verify that the mapping state is
+	  unwound, and check that the current DMA devices identify the owner of
+	  those mappings when the error is returned. They also cover a
+	  successful mapping and a message which requires no mapping.
+
+	  If unsure say N.
+
 config SPI_LOOPBACK_TEST
 	tristate "spi loopback test framework support"
 	depends on m
diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
index 9fa12498c..f693699f8 100644
--- a/drivers/spi/Makefile
+++ b/drivers/spi/Makefile
@@ -13,6 +13,7 @@ obj-$(CONFIG_SPI_MUX)			+= spi-mux.o
 obj-$(CONFIG_SPI_OFFLOAD)		+= spi-offload.o
 obj-$(CONFIG_SPI_SPIDEV)		+= spidev.o
 obj-$(CONFIG_SPI_LOOPBACK_TEST)		+= spi-loopback-test.o
+obj-$(CONFIG_SPI_DMA_KUNIT_TEST)	+= tests/
 
 # SPI master controller drivers (bus)
 obj-$(CONFIG_SPI_AIROHA_SNFI)		+= spi-airoha-snfi.o
diff --git a/drivers/spi/internals.h b/drivers/spi/internals.h
index 1f459b895..c56c190b0 100644
--- a/drivers/spi/internals.h
+++ b/drivers/spi/internals.h
@@ -5,8 +5,8 @@
  *
  * Author: Boris Brezillon <[email protected]>
  *
- * Helpers needed by the spi or spi-mem logic. Should not be used outside of
- * spi-mem.c and spi.c.
+ * Helpers needed by the SPI core and its tests. Should not be used outside
+ * drivers/spi/.
  */
 
 #ifndef __LINUX_SPI_INTERNALS_H
@@ -20,6 +20,11 @@
 void spi_flush_queue(struct spi_controller *ctrl);
 
 #ifdef CONFIG_HAS_DMA
+#if IS_ENABLED(CONFIG_KUNIT)
+int __spi_map_msg(struct spi_controller *ctlr, struct spi_message *msg);
+int __spi_unmap_msg(struct spi_controller *ctlr, struct spi_message *msg);
+#endif
+
 int spi_map_buf(struct spi_controller *ctlr, struct device *dev,
 		struct sg_table *sgt, void *buf, size_t len,
 		enum dma_data_direction dir);
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index e5b1531b9..6be7987ed 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -4,6 +4,7 @@
 // Copyright (C) 2005 David Brownell
 // Copyright (C) 2008 Secret Lab Technologies Ltd.
 
+#include <kunit/visibility.h>
 #include <linux/acpi.h>
 #include <linux/cache.h>
 #include <linux/clk/clk-conf.h>
@@ -1231,7 +1232,8 @@ void spi_unmap_buf(struct spi_controller *ctlr, struct device *dev,
 	spi_unmap_buf_attrs(ctlr, dev, sgt, dir, 0);
 }
 
-static int __spi_unmap_msg(struct spi_controller *ctlr, struct spi_message *msg)
+VISIBLE_IF_KUNIT
+int __spi_unmap_msg(struct spi_controller *ctlr, struct spi_message *msg)
 {
 	struct device *rx_dev = ctlr->cur_rx_dma_dev;
 	struct device *tx_dev = ctlr->cur_tx_dma_dev;
@@ -1254,8 +1256,10 @@ static int __spi_unmap_msg(struct spi_controller *ctlr, struct spi_message *msg)
 
 	return 0;
 }
+EXPORT_SYMBOL_IF_KUNIT(__spi_unmap_msg);
 
-static int __spi_map_msg(struct spi_controller *ctlr, struct spi_message *msg)
+VISIBLE_IF_KUNIT
+int __spi_map_msg(struct spi_controller *ctlr, struct spi_message *msg)
 {
 	struct device *tx_dev, *rx_dev;
 	struct spi_transfer *xfer;
@@ -1321,6 +1325,7 @@ static int __spi_map_msg(struct spi_controller *ctlr, struct spi_message *msg)
 
 	return ret;
 }
+EXPORT_SYMBOL_IF_KUNIT(__spi_map_msg);
 
 static void spi_dma_sync_for_device(struct spi_controller *ctlr,
 				    struct spi_transfer *xfer)
diff --git a/drivers/spi/tests/Makefile b/drivers/spi/tests/Makefile
new file mode 100644
index 000000000..26689e0cb
--- /dev/null
+++ b/drivers/spi/tests/Makefile
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+obj-$(CONFIG_SPI_DMA_KUNIT_TEST) += spi-dma-kunit.o
diff --git a/drivers/spi/tests/spi-dma-kunit.c b/drivers/spi/tests/spi-dma-kunit.c
new file mode 100644
index 000000000..ee5476ff3
--- /dev/null
+++ b/drivers/spi/tests/spi-dma-kunit.c
@@ -0,0 +1,259 @@
+// SPDX-License-Identifier: GPL-2.0
+// KUnit tests for the SPI core DMA mapping error paths.
+//
+// A mapping error must clear all SG tables and *_sg_mapped flags while
+// cur_{tx,rx}_dma_dev identify the devices used for the attempted mapping.
+// Zero-length transfers make sg_alloc_table() fail with -EINVAL, providing
+// deterministic failure injection without test hooks.
+
+#include <kunit/device.h>
+#include <kunit/test.h>
+#include <linux/dma-mapping.h>
+#include <linux/limits.h>
+#include <linux/spi/spi.h>
+
+#include "../internals.h"
+
+MODULE_IMPORT_NS("EXPORTED_FOR_KUNIT_TESTING");
+
+#define SPI_DMA_TEST_LEN		256
+#define SPI_DMA_TEST_XFERS		2
+
+struct spi_dma_test_ctx {
+	struct spi_controller	*ctlr;
+	struct spi_device	*spi;
+	struct device		*dma_dev;
+	struct device		*stale_dma_dev;
+	struct spi_transfer	xfer[SPI_DMA_TEST_XFERS];
+	struct spi_message	msg;
+	void			*buf[SPI_DMA_TEST_XFERS * 2];
+};
+
+static bool spi_dma_test_can_dma(struct spi_controller *ctlr,
+				 struct spi_device *spi,
+				 struct spi_transfer *xfer)
+{
+	/* Opt every transfer into the core DMA mapping path. */
+	return true;
+}
+
+/*
+ * A bare controller is sufficient because the mapping helpers do not
+ * dereference ctlr->dev. With dma_tx and dma_rx unset, both directions use
+ * dma_map_dev, so the controller need not be registered.
+ */
+static struct spi_dma_test_ctx *spi_dma_test_ctx_new(struct kunit *test)
+{
+	struct spi_dma_test_ctx *ctx;
+
+	ctx = kunit_kzalloc(test, sizeof(*ctx), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ctx);
+
+	ctx->dma_dev = kunit_device_register(test, "spi-dma-error-path");
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ctx->dma_dev);
+	ctx->stale_dma_dev =
+		kunit_device_register(test, "spi-dma-stale-device");
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ctx->stale_dma_dev);
+
+	/* Keep both devices valid if an assertion aborts the test. */
+	KUNIT_ASSERT_EQ(test, 0,
+			dma_coerce_mask_and_coherent(ctx->dma_dev,
+						     DMA_BIT_MASK(64)));
+	KUNIT_ASSERT_EQ(test, 0,
+			dma_coerce_mask_and_coherent(ctx->stale_dma_dev,
+						     DMA_BIT_MASK(64)));
+
+	ctx->ctlr = kunit_kzalloc(test, sizeof(*ctx->ctlr), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ctx->ctlr);
+
+	ctx->spi = kunit_kzalloc(test, sizeof(*ctx->spi), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ctx->spi);
+
+	ctx->ctlr->can_dma = spi_dma_test_can_dma;
+	ctx->ctlr->dma_map_dev = ctx->dma_dev;
+	/* Normally initialized by spi_register_controller(). */
+	ctx->ctlr->max_dma_len = INT_MAX;
+
+	ctx->spi->controller = ctx->ctlr;
+	spi_message_init(&ctx->msg);
+	ctx->msg.spi = ctx->spi;
+
+	return ctx;
+}
+
+static void *spi_dma_test_buf(struct kunit *test, struct spi_dma_test_ctx *ctx,
+			      unsigned int slot)
+{
+	KUNIT_ASSERT_LT(test, slot, ARRAY_SIZE(ctx->buf));
+
+	ctx->buf[slot] = kunit_kzalloc(test, SPI_DMA_TEST_LEN, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ctx->buf[slot]);
+
+	return ctx->buf[slot];
+}
+
+/*
+ * Emulate DMA devices retained from an earlier message. Using valid devices
+ * also lets the unfixed path reach the assertions instead of dereferencing
+ * NULL during cleanup.
+ */
+static void spi_dma_test_pin_stale_dma_devs(struct spi_dma_test_ctx *ctx)
+{
+	ctx->ctlr->cur_tx_dma_dev = ctx->stale_dma_dev;
+	ctx->ctlr->cur_rx_dma_dev = ctx->stale_dma_dev;
+}
+
+static void spi_dma_test_assert_dma_devs_published(struct kunit *test,
+						   struct spi_dma_test_ctx *ctx)
+{
+	KUNIT_ASSERT_PTR_EQ(test, ctx->ctlr->cur_tx_dma_dev, ctx->dma_dev);
+	KUNIT_ASSERT_PTR_EQ(test, ctx->ctlr->cur_rx_dma_dev, ctx->dma_dev);
+}
+
+static void spi_dma_test_assert_nothing_mapped(struct kunit *test,
+					       struct spi_dma_test_ctx *ctx,
+					       unsigned int nr_xfers)
+{
+	unsigned int i;
+
+	for (i = 0; i < nr_xfers; i++) {
+		KUNIT_ASSERT_FALSE_MSG(test, ctx->xfer[i].tx_sg_mapped,
+				       "xfer[%u] still claims a TX mapping after __spi_map_msg() failed",
+				       i);
+		KUNIT_ASSERT_FALSE_MSG(test, ctx->xfer[i].rx_sg_mapped,
+				       "xfer[%u] still claims an RX mapping after __spi_map_msg() failed",
+				       i);
+		KUNIT_EXPECT_NULL(test, ctx->xfer[i].tx_sg.sgl);
+		KUNIT_EXPECT_EQ(test, ctx->xfer[i].tx_sg.orig_nents, 0U);
+		KUNIT_EXPECT_EQ(test, ctx->xfer[i].tx_sg.nents, 0U);
+		KUNIT_EXPECT_NULL(test, ctx->xfer[i].rx_sg.sgl);
+		KUNIT_EXPECT_EQ(test, ctx->xfer[i].rx_sg.orig_nents, 0U);
+		KUNIT_EXPECT_EQ(test, ctx->xfer[i].rx_sg.nents, 0U);
+	}
+}
+
+/*
+ * xfer0 maps TX and RX; zero-length xfer1 then fails its TX mapping.
+ * The failure must unwind xfer0 and update cur_*_dma_dev.
+ */
+static void spi_dma_later_tx_fail_rolls_back_earlier(struct kunit *test)
+{
+	struct spi_dma_test_ctx *ctx = spi_dma_test_ctx_new(test);
+	int ret;
+
+	ctx->xfer[0].tx_buf = spi_dma_test_buf(test, ctx, 0);
+	ctx->xfer[0].rx_buf = spi_dma_test_buf(test, ctx, 1);
+	ctx->xfer[0].len = SPI_DMA_TEST_LEN;
+
+	ctx->xfer[1].tx_buf = spi_dma_test_buf(test, ctx, 2);
+	ctx->xfer[1].rx_buf = NULL;
+	ctx->xfer[1].len = 0;			/* forces -EINVAL */
+
+	spi_message_add_tail(&ctx->xfer[0], &ctx->msg);
+	spi_message_add_tail(&ctx->xfer[1], &ctx->msg);
+
+	spi_dma_test_pin_stale_dma_devs(ctx);
+
+	ret = __spi_map_msg(ctx->ctlr, &ctx->msg);
+	KUNIT_ASSERT_EQ(test, ret, -EINVAL);
+
+	spi_dma_test_assert_dma_devs_published(test, ctx);
+	spi_dma_test_assert_nothing_mapped(test, ctx, SPI_DMA_TEST_XFERS);
+
+	KUNIT_EXPECT_EQ(test, 0, __spi_unmap_msg(ctx->ctlr, &ctx->msg));
+}
+
+/*
+ * xfer0 maps TX and RX; zero-length RX-only xfer1 then fails.
+ * The failure must unwind xfer0 without leaving either mapping flag set.
+ */
+static void spi_dma_later_rx_fail_rolls_back_earlier(struct kunit *test)
+{
+	struct spi_dma_test_ctx *ctx = spi_dma_test_ctx_new(test);
+	int ret;
+
+	ctx->xfer[0].tx_buf = spi_dma_test_buf(test, ctx, 0);
+	ctx->xfer[0].rx_buf = spi_dma_test_buf(test, ctx, 1);
+	ctx->xfer[0].len = SPI_DMA_TEST_LEN;
+
+	ctx->xfer[1].tx_buf = NULL;
+	ctx->xfer[1].rx_buf = spi_dma_test_buf(test, ctx, 2);
+	ctx->xfer[1].len = 0;			/* forces -EINVAL */
+
+	spi_message_add_tail(&ctx->xfer[0], &ctx->msg);
+	spi_message_add_tail(&ctx->xfer[1], &ctx->msg);
+
+	spi_dma_test_pin_stale_dma_devs(ctx);
+
+	ret = __spi_map_msg(ctx->ctlr, &ctx->msg);
+	KUNIT_ASSERT_EQ(test, ret, -EINVAL);
+
+	spi_dma_test_assert_dma_devs_published(test, ctx);
+	spi_dma_test_assert_nothing_mapped(test, ctx, SPI_DMA_TEST_XFERS);
+
+	KUNIT_EXPECT_EQ(test, 0, __spi_unmap_msg(ctx->ctlr, &ctx->msg));
+}
+
+/* Ensure the error unwind does not affect successful mappings. */
+static void spi_dma_map_success_publishes_dma_devs(struct kunit *test)
+{
+	struct spi_dma_test_ctx *ctx = spi_dma_test_ctx_new(test);
+	int ret;
+
+	ctx->xfer[0].tx_buf = spi_dma_test_buf(test, ctx, 0);
+	ctx->xfer[0].rx_buf = spi_dma_test_buf(test, ctx, 1);
+	ctx->xfer[0].len = SPI_DMA_TEST_LEN;
+
+	spi_message_add_tail(&ctx->xfer[0], &ctx->msg);
+
+	ret = __spi_map_msg(ctx->ctlr, &ctx->msg);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+
+	KUNIT_EXPECT_TRUE(test, ctx->xfer[0].tx_sg_mapped);
+	KUNIT_EXPECT_TRUE(test, ctx->xfer[0].rx_sg_mapped);
+	KUNIT_EXPECT_PTR_EQ(test, ctx->ctlr->cur_tx_dma_dev, ctx->dma_dev);
+	KUNIT_EXPECT_PTR_EQ(test, ctx->ctlr->cur_rx_dma_dev, ctx->dma_dev);
+
+	KUNIT_EXPECT_EQ(test, 0, __spi_unmap_msg(ctx->ctlr, &ctx->msg));
+
+	KUNIT_EXPECT_FALSE(test, ctx->xfer[0].tx_sg_mapped);
+	KUNIT_EXPECT_FALSE(test, ctx->xfer[0].rx_sg_mapped);
+	KUNIT_EXPECT_NULL(test, ctx->xfer[0].tx_sg.sgl);
+	KUNIT_EXPECT_NULL(test, ctx->xfer[0].rx_sg.sgl);
+}
+
+/* A transfer without buffers requires no DMA mapping. */
+static void spi_dma_map_nothing_is_success(struct kunit *test)
+{
+	struct spi_dma_test_ctx *ctx = spi_dma_test_ctx_new(test);
+	int ret;
+
+	ctx->xfer[0].tx_buf = NULL;
+	ctx->xfer[0].rx_buf = NULL;
+	ctx->xfer[0].len = SPI_DMA_TEST_LEN;
+
+	spi_message_add_tail(&ctx->xfer[0], &ctx->msg);
+
+	ret = __spi_map_msg(ctx->ctlr, &ctx->msg);
+	KUNIT_EXPECT_EQ(test, ret, 0);
+
+	spi_dma_test_assert_nothing_mapped(test, ctx, 1);
+}
+
+static struct kunit_case spi_dma_error_path_cases[] = {
+	KUNIT_CASE(spi_dma_later_tx_fail_rolls_back_earlier),
+	KUNIT_CASE(spi_dma_later_rx_fail_rolls_back_earlier),
+	KUNIT_CASE(spi_dma_map_success_publishes_dma_devs),
+	KUNIT_CASE(spi_dma_map_nothing_is_success),
+	{}
+};
+
+static struct kunit_suite spi_dma_error_path_suite = {
+	.name = "spi_dma",
+	.test_cases = spi_dma_error_path_cases,
+};
+
+kunit_test_suite(spi_dma_error_path_suite);
+
+MODULE_DESCRIPTION("KUnit tests for SPI core DMA mapping");
+MODULE_LICENSE("GPL");
diff --git a/tools/testing/kunit/configs/all_tests.config b/tools/testing/kunit/configs/all_tests.config
index bccc2c771..7bdcbdec2 100644
--- a/tools/testing/kunit/configs/all_tests.config
+++ b/tools/testing/kunit/configs/all_tests.config
@@ -21,6 +21,7 @@ CONFIG_VFAT_FS=y
 CONFIG_PCI=y
 CONFIG_USB4=y
 CONFIG_I2C=y
+CONFIG_SPI=y
 
 CONFIG_NET=y
 CONFIG_MCTP=y
diff --git a/tools/testing/kunit/configs/default.config b/tools/testing/kunit/configs/default.config
index e67af7b9f..2f24147c9 100644
--- a/tools/testing/kunit/configs/default.config
+++ b/tools/testing/kunit/configs/default.config
@@ -1,3 +1,4 @@
 CONFIG_KUNIT=y
 CONFIG_KUNIT_EXAMPLE_TEST=y
 CONFIG_KUNIT_ALL_TESTS=y
+CONFIG_SPI=y
-- 
2.43.0