[PATCH char-misc-next v2 3/4] issei: host_client: add dma allocation support

[Alexander Usyskin <alexander.usyskin@intel.com>]

Add functions to allow dedicated DMA buffer allocated on current
hardware device per host client.

Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
---
 drivers/misc/issei/host_client.c | 66 ++++++++++++++++++++++++++++++++++++++++
 drivers/misc/issei/host_client.h | 12 ++++++++
 drivers/misc/issei/issei_dev.h   |  3 ++
 3 files changed, 81 insertions(+)

diff --git a/drivers/misc/issei/host_client.c b/drivers/misc/issei/host_client.c
index d16b5835c619..751296e3dc25 100644
--- a/drivers/misc/issei/host_client.c
+++ b/drivers/misc/issei/host_client.c
@@ -2,6 +2,7 @@
 /* Copyright (C) 2023-2026 Intel Corporation */
 #include <linux/cleanup.h>
 #include <linux/dev_printk.h>
+#include <linux/dma-mapping.h>
 #include <linux/err.h>
 #include <linux/fs.h>
 #include <linux/kobject.h>
@@ -112,6 +113,17 @@ static void __issei_cl_disconnect(struct issei_device *idev, struct issei_host_c
 	cl_dbg(idev, cl, "Disconnected\n");
 }
 
+static void __issei_cl_dma_unmap(struct issei_host_client *cl)
+{
+	if (!cl->dma_size)
+		return;
+
+	dma_free_coherent(cl->idev->parent, cl->dma_size, cl->dma_vaddr, cl->dma_daddr);
+	cl->dma_size = 0;
+	cl->dma_vaddr = NULL;
+	cl->dma_daddr = 0;
+}
+
 static void __issei_cl_init(struct issei_host_client *cl, struct issei_device *idev,
 			    u16 id, struct file *fp)
 {
@@ -185,6 +197,8 @@ void issei_cl_remove(struct issei_host_client *cl)
 
 	__issei_cl_disconnect(idev, cl);
 
+	__issei_cl_dma_unmap(cl);
+
 	cl_dbg(idev, cl, "Removed\n");
 	kfree(cl);
 }
@@ -521,3 +535,55 @@ void issei_cl_clean_all_wbuf(struct issei_host_client *cl)
 
 	__issei_cl_clean_all_wbuf(idev, cl);
 }
+
+/**
+ * issei_cl_dma_map - allocate DMA mapping for client
+ *
+ * @cl: host client
+ * @size: memory size to allocate
+ * @daddr: pointer for buffer DMA address
+ * @vaddr: pointer for buffer virtual address
+ *
+ * Return: 0 on success, < 0 on error
+ */
+int issei_cl_dma_map(struct issei_host_client *cl, size_t size,
+		     dma_addr_t *daddr, void **vaddr)
+{
+	struct issei_device *idev = cl->idev;
+
+	if (size == 0 || size > ISSEI_HOST_DMA_MAX_SIZE) {
+		cl_err(idev, cl, "The size is out of bounds.\n");
+		return -EINVAL;
+	}
+
+	guard(mutex)(&idev->client_lock);
+
+	if (cl->dma_size) {
+		cl_err(idev, cl, "DMA already allocated.\n");
+		return -EALREADY;
+	}
+
+	cl->dma_vaddr = dma_alloc_coherent(cl->idev->parent, size, &cl->dma_daddr, GFP_KERNEL);
+	if (!cl->dma_vaddr)
+		return -ENOMEM;
+
+	cl->dma_size = size;
+
+	*daddr = cl->dma_daddr;
+	*vaddr = cl->dma_vaddr;
+	return 0;
+}
+
+/**
+ * issei_cl_dma_unmap - deallocate DMA mapping for client
+ *
+ * @cl: host client
+ */
+void issei_cl_dma_unmap(struct issei_host_client *cl)
+{
+	struct issei_device *idev = cl->idev;
+
+	guard(mutex)(&idev->client_lock);
+
+	__issei_cl_dma_unmap(cl);
+}
diff --git a/drivers/misc/issei/host_client.h b/drivers/misc/issei/host_client.h
index 05e2f4ade9c3..987cee609676 100644
--- a/drivers/misc/issei/host_client.h
+++ b/drivers/misc/issei/host_client.h
@@ -38,6 +38,10 @@ enum issei_host_client_state {
  * @read_wait: waitqueue for read object
  * @read_data: received data pointer
  * @read_data_size: received data size
+ *
+ * @dma_vaddr: allocated DMA buffer virtual address
+ * @dma_daddr: allocated DMA buffer DMA address
+ * @dma_size: allocated DMA buffer size, zero if no buffer allocated
  */
 struct issei_host_client {
 	struct list_head list;
@@ -54,6 +58,10 @@ struct issei_host_client {
 	wait_queue_head_t read_wait;
 	u8 *read_data;
 	size_t read_data_size;
+
+	void *dma_vaddr;
+	dma_addr_t dma_daddr;
+	size_t dma_size;
 };
 
 struct issei_host_client *issei_cl_create(struct issei_device *idev, struct file *fp);
@@ -72,4 +80,8 @@ int issei_cl_check_read(struct issei_host_client *cl);
 int issei_cl_check_write(struct issei_host_client *cl);
 void issei_cl_clean_all_wbuf(struct issei_host_client *cl);
 
+int issei_cl_dma_map(struct issei_host_client *cl, size_t size,
+		     dma_addr_t *daddr, void **vaddr);
+void issei_cl_dma_unmap(struct issei_host_client *cl);
+
 #endif /* ISSEI_HOST_CLIENT_H_ */
diff --git a/drivers/misc/issei/issei_dev.h b/drivers/misc/issei/issei_dev.h
index b47c4a7c2da4..244dc62ad85f 100644
--- a/drivers/misc/issei/issei_dev.h
+++ b/drivers/misc/issei/issei_dev.h
@@ -6,6 +6,7 @@
 #include <linux/device.h>
 #include <linux/mutex.h>
 #include <linux/sched.h>
+#include <linux/sizes.h>
 #include <linux/time64.h>
 #include <linux/types.h>
 #include <linux/wait.h>
@@ -31,6 +32,8 @@ extern struct class *issei_class;
 #define ISSEI_STOP_TIMEOUT_MSEC         500
 #define ISSEI_WRITE_TIMEOUT_MSEC        (MSEC_PER_SEC)
 
+#define ISSEI_HOST_DMA_MAX_SIZE	        SZ_64M
+
 /**
  * struct issei_write_buf - write buffer object
  * @list: linked list pointer

-- 
2.53.0