[PATCH v4 12/25] dmaengine: sdxi: Add client context allocation API
From: Nathan Lynch via B4 Relay
Date: Tue Nov 03 2026 - 22:04:02 EST
From: Nathan Lynch <nathan.lynch@xxxxxxx>
Allocate and publish client contexts, track their IDs in a per-device
xarray, and release them during device teardown.
Signed-off-by: Nathan Lynch <nathan.lynch@xxxxxxx>
---
drivers/dma/sdxi/context.c | 95 ++++++++++++++++++++++++++++++++++++++++++++++
drivers/dma/sdxi/context.h | 12 ++++++
drivers/dma/sdxi/device.c | 4 ++
drivers/dma/sdxi/sdxi.h | 2 +
4 files changed, 113 insertions(+)
diff --git a/drivers/dma/sdxi/context.c b/drivers/dma/sdxi/context.c
index ebce30dc462a..f52479ecf96a 100644
--- a/drivers/dma/sdxi/context.c
+++ b/drivers/dma/sdxi/context.c
@@ -44,6 +44,10 @@ static void sdxi_free_cxt(struct sdxi_cxt *cxt)
{
struct sdxi_dev *sdxi = cxt->sdxi;
+ /* Release the id if this is a client context. */
+ if (cxt->id)
+ WARN_ON(xa_erase(&sdxi->client_cxts, cxt->id) != cxt);
+
if (cxt->cxt_ctl)
dma_pool_free(sdxi->cxt_ctl_pool, cxt->cxt_ctl,
cxt->cxt_ctl_dma);
@@ -248,3 +252,94 @@ int sdxi_admin_cxt_init(struct sdxi_dev *sdxi)
return devm_add_action_or_reset(sdxi->dev, free_admin_cxt, sdxi);
}
+
+/*
+ * Temporary owner for context id until it can be assigned to a
+ * context object; enables scope-based cleanup.
+ */
+struct sdxi_cxt_id {
+ struct sdxi_dev *sdxi;
+ u16 index;
+};
+
+static void sdxi_cxt_id_dtor(const struct sdxi_cxt_id *cxt_id)
+{
+ if (cxt_id->index == 0)
+ return;
+ WARN_ON(xa_erase(&cxt_id->sdxi->client_cxts, cxt_id->index) != NULL);
+}
+
+static struct sdxi_cxt_id sdxi_cxt_id_ctor(struct sdxi_dev *sdxi)
+{
+ struct xa_limit limit = XA_LIMIT(1, sdxi->max_cxtid);
+ u32 index;
+
+ return (struct sdxi_cxt_id) {
+ .sdxi = sdxi,
+ .index = xa_alloc(&sdxi->client_cxts, &index, NULL,
+ limit, GFP_KERNEL) ? 0 : (u16)index,
+ };
+}
+
+DEFINE_CLASS(sdxi_cxt_id, struct sdxi_cxt_id, sdxi_cxt_id_dtor(&_T),
+ sdxi_cxt_id_ctor(sdxi), struct sdxi_dev *sdxi)
+
+static bool sdxi_cxt_id_valid(const struct sdxi_cxt_id *cxt_id)
+{
+ return cxt_id->index > 0;
+}
+
+/*
+ * Transfer the reserved ID to the context and store its pointer in client_cxts.
+ * sdxi_free_cxt() releases the ID.
+ */
+static void sdxi_cxt_id_assign(struct sdxi_cxt *cxt, struct sdxi_cxt_id *cxt_id)
+{
+ /* We reserved the space in the constructor so this should not fail. */
+ WARN_ON(xa_store(&cxt_id->sdxi->client_cxts,
+ cxt_id->index, cxt, GFP_KERNEL));
+ cxt->id = cxt_id->index;
+ cxt_id->index = 0;
+}
+
+/*
+ * Allocate a context for in-kernel use. Starting the context is the
+ * caller's responsibility.
+ */
+struct sdxi_cxt *sdxi_cxt_new(struct sdxi_dev *sdxi)
+{
+ /*
+ * Ensure an ID is available before allocating memory for the
+ * context and its control structures.
+ */
+ CLASS(sdxi_cxt_id, id)(sdxi);
+ if (!sdxi_cxt_id_valid(&id))
+ return NULL;
+
+ struct sdxi_cxt *cxt __free(sdxi_cxt) = sdxi_alloc_cxt(sdxi);
+ if (!cxt)
+ return NULL;
+
+ sdxi_cxt_id_assign(cxt, &id);
+
+ cxt->sq->doorbell = sdxi->dbs + cxt->id * sdxi->db_stride;
+
+ if (sdxi_publish_cxt(cxt))
+ return NULL;
+
+ return_ptr(cxt);
+}
+
+/*
+ * Release all tracked client contexts during device teardown. Hardware access
+ * to client resources must have ceased before release.
+ */
+void sdxi_client_cxts_exit(struct sdxi_dev *sdxi)
+{
+ struct sdxi_cxt *cxt;
+ unsigned long index;
+
+ xa_for_each(&sdxi->client_cxts, index, cxt)
+ sdxi_free_cxt(cxt);
+ xa_destroy(&sdxi->client_cxts);
+}
diff --git a/drivers/dma/sdxi/context.h b/drivers/dma/sdxi/context.h
index ae1584d00b54..28cd7ed401f8 100644
--- a/drivers/dma/sdxi/context.h
+++ b/drivers/dma/sdxi/context.h
@@ -39,5 +39,17 @@ struct sdxi_cxt {
};
int sdxi_admin_cxt_init(struct sdxi_dev *sdxi);
+struct sdxi_cxt *sdxi_cxt_new(struct sdxi_dev *sdxi);
+void sdxi_client_cxts_exit(struct sdxi_dev *sdxi);
+
+static inline struct sdxi_cxt *to_admin_cxt(const struct sdxi_cxt *cxt)
+{
+ return cxt->sdxi->admin_cxt;
+}
+
+static inline bool sdxi_cxt_is_admin(const struct sdxi_cxt *cxt)
+{
+ return cxt == to_admin_cxt(cxt);
+}
#endif /* DMA_SDXI_CONTEXT_H */
diff --git a/drivers/dma/sdxi/device.c b/drivers/dma/sdxi/device.c
index d5a5b8d43391..8786be71d3e3 100644
--- a/drivers/dma/sdxi/device.c
+++ b/drivers/dma/sdxi/device.c
@@ -19,6 +19,7 @@
#include <linux/sizes.h>
#include <linux/slab.h>
#include <linux/time.h>
+#include <linux/xarray.h>
#include "context.h"
#include "hw.h"
@@ -436,6 +437,7 @@ int sdxi_register(struct device *dev, const struct sdxi_bus_ops *ops)
sdxi->dev = dev;
sdxi->bus_ops = ops;
+ xa_init_flags(&sdxi->client_cxts, XA_FLAGS_ALLOC1);
dev_set_drvdata(dev, sdxi);
err = sdxi->bus_ops->init(sdxi);
@@ -454,7 +456,9 @@ void sdxi_unregister(struct device *dev)
{
struct sdxi_dev *sdxi = dev_get_drvdata(dev);
+ /* Stop/reset is best effort if the hardware cannot be quiesced. */
sdxi_dev_stop(sdxi);
+ sdxi_client_cxts_exit(sdxi);
}
EXPORT_SYMBOL_NS_GPL(sdxi_unregister, "SDXI");
diff --git a/drivers/dma/sdxi/sdxi.h b/drivers/dma/sdxi/sdxi.h
index 631a605ea62f..aaa43eab00b3 100644
--- a/drivers/dma/sdxi/sdxi.h
+++ b/drivers/dma/sdxi/sdxi.h
@@ -12,6 +12,7 @@
#include <linux/dev_printk.h>
#include <linux/io.h>
#include <linux/types.h>
+#include <linux/xarray.h>
#include "mmio.h"
@@ -61,6 +62,7 @@ struct sdxi_dev {
struct dma_pool *cxt_ctl_pool;
struct sdxi_cxt *admin_cxt;
+ struct xarray client_cxts; /* context id -> (struct sdxi_cxt *) */
bool has_mailbox;
--
2.56.0