[PATCH 10/23] dmaengine: sdxi: Complete administrative context jump start

Nathan Lynch via B4 Relay
2026-04-10T13:07:50Z

Now that the SDXI function has been placed in active state, the admin
context can finally be started by writing its doorbell. Introduce
sdxi_cxt_push_doorbell() to pair the necessary barrier with the
doorbell update.

Co-developed-by: Wei Huang <wei.huang2@amd.com>
Signed-off-by: Wei Huang <wei.huang2@amd.com>
Signed-off-by: Nathan Lynch <nathan.lynch@amd.com>
---
drivers/dma/sdxi/context.c | 8 ++++++++
drivers/dma/sdxi/context.h | 2 ++
drivers/dma/sdxi/device.c | 15 ++++++++++++++-
3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/drivers/dma/sdxi/context.c b/drivers/dma/sdxi/context.c
index 097d871e530f..934c487b4774 100644
--- a/drivers/dma/sdxi/context.c
+++ b/drivers/dma/sdxi/context.c
@@ -16,6 +16,7 @@
#include <linux/dmapool.h>
#include <linux/errno.h>
#include <linux/iommu.h>
+#include <linux/io-64-nonatomic-lo-hi.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <asm/barrier.h>
@@ -258,6 +259,13 @@ static int sdxi_publish_cxt(const struct sdxi_cxt *cxt)
/* todo: need to send DSC_CXT_UPD to admin */
}

+void sdxi_cxt_push_doorbell(struct sdxi_cxt *cxt, u64 index)
+{
+ /* Ensure preceding write index increment is visible. */
+ dma_wmb();
+ iowrite64(index, cxt->db);
+}
+
static void free_admin_cxt(void *ptr)
{
struct sdxi_dev *sdxi = ptr;
diff --git a/drivers/dma/sdxi/context.h b/drivers/dma/sdxi/context.h
index bbde1fd49af3..c34acd730acb 100644
--- a/drivers/dma/sdxi/context.h
+++ b/drivers/dma/sdxi/context.h
@@ -58,4 +58,6 @@ struct sdxi_cxt {

int sdxi_admin_cxt_init(struct sdxi_dev *sdxi);

+void sdxi_cxt_push_doorbell(struct sdxi_cxt *cxt, u64 index);
+
#endif /* DMA_SDXI_CONTEXT_H */
diff --git a/drivers/dma/sdxi/device.c b/drivers/dma/sdxi/device.c
index 145aa098c269..15f61d1ce490 100644
--- a/drivers/dma/sdxi/device.c
+++ b/drivers/dma/sdxi/device.c
@@ -244,7 +244,20 @@ static int sdxi_fn_activate(struct sdxi_dev *sdxi)
* SDXI 1.0 4.1.8.9: Set MMIO_CTL0.fn_gsr to GSRV_ACTIVE and
* wait for MMIO_STS0.fn_gsv to reach GSV_ACTIVE or GSV_ERROR.
*/
- return sdxi_dev_start(sdxi);
+ err = sdxi_dev_start(sdxi);
+ if (err)
+ return err;
+
+ /*
+ * SDXI 1.0 4.1.8.10.b: Start the admin context using method
+ * #3 ("Jump Start 1") from 4.3.4 Starting A Context and
+ * Context Signaling. We haven't queued any descriptors to the
+ * admin context at this point, so the appropriate value for
+ * the doorbell is 0.
+ */
+ sdxi_cxt_push_doorbell(sdxi->admin_cxt, 0);
+
+ return 0;
}

static int sdxi_create_dma_pool(struct sdxi_dev *sdxi, struct dma_pool **pool,

--
2.53.0