misc: fastrpc: Add support for multiple PD from one process

Memory intensive applications(which requires more tha 4GB) that wants
to offload tasks to DSP might have to split the tasks to multiple
user PD to make the resources available.

For every call to DSP, fastrpc driver passes the process tgid which
works as an identifier for the DSP to enqueue the tasks to specific PD.
With current design, if any process opens device node more than once
and makes PD init request, same tgid will be passed to DSP which will
be considered a bad request and this will result in failure as the same
identifier cannot be used for multiple DSP PD.

Assign and pass a client ID to DSP which would be assigned during device
open and will be dependent on the index of session allocated for the PD.
This will allow the same process to open the device more than once and
spawn multiple dynamic PD for ease of processing.

Signed-off-by: Ekansh Gupta <quic_ekangupt@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20250110134308.123739-2-srinivas.kandagatla@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/fastrpc.c

@@ -299,7 +299,7 @@ struct fastrpc_user {
 	struct fastrpc_session_ctx *sctx;
 	struct fastrpc_buf *init_mem;
 
-	int tgid;
+	int client_id;
 	int pd;
 	bool is_secure_dev;
 	/* Lock for lists */
@@ -614,7 +614,7 @@ static struct fastrpc_invoke_ctx *fastrpc_context_alloc(
 	ctx->sc = sc;
 	ctx->retval = -1;
 	ctx->pid = current->pid;
-	ctx->tgid = user->tgid;
+	ctx->tgid = user->client_id;
 	ctx->cctx = cctx;
 	init_completion(&ctx->work);
 	INIT_WORK(&ctx->put_work, fastrpc_context_put_wq);
@@ -1115,7 +1115,7 @@ static int fastrpc_invoke_send(struct fastrpc_session_ctx *sctx,
 	int ret;
 
 	cctx = fl->cctx;
-	msg->pid = fl->tgid;
+	msg->pid = fl->client_id;
 	msg->tid = current->pid;
 
 	if (kernel)
@@ -1293,7 +1293,7 @@ static int fastrpc_init_create_static_process(struct fastrpc_user *fl,
 		}
 	}
 
-	inbuf.pgid = fl->tgid;
+	inbuf.pgid = fl->client_id;
 	inbuf.namelen = init.namelen;
 	inbuf.pageslen = 0;
 	fl->pd = USER_PD;
@@ -1395,7 +1395,7 @@ static int fastrpc_init_create_process(struct fastrpc_user *fl,
 		goto err;
 	}
 
-	inbuf.pgid = fl->tgid;
+	inbuf.pgid = fl->client_id;
 	inbuf.namelen = strlen(current->comm) + 1;
 	inbuf.filelen = init.filelen;
 	inbuf.pageslen = 1;
@@ -1469,8 +1469,9 @@ static int fastrpc_init_create_process(struct fastrpc_user *fl,
 }
 
 static struct fastrpc_session_ctx *fastrpc_session_alloc(
-					struct fastrpc_channel_ctx *cctx)
+					struct fastrpc_user *fl)
 {
+	struct fastrpc_channel_ctx *cctx = fl->cctx;
 	struct fastrpc_session_ctx *session = NULL;
 	unsigned long flags;
 	int i;
@@ -1480,6 +1481,8 @@ static struct fastrpc_session_ctx *fastrpc_session_alloc(
 		if (!cctx->session[i].used && cctx->session[i].valid) {
 			cctx->session[i].used = true;
 			session = &cctx->session[i];
+			/* any non-zero ID will work, session_idx + 1 is the simplest one */
+			fl->client_id = i + 1;
 			break;
 		}
 	}
@@ -1504,7 +1507,7 @@ static int fastrpc_release_current_dsp_process(struct fastrpc_user *fl)
 	int tgid = 0;
 	u32 sc;
 
-	tgid = fl->tgid;
+	tgid = fl->client_id;
 	args[0].ptr = (u64)(uintptr_t) &tgid;
 	args[0].length = sizeof(tgid);
 	args[0].fd = -1;
@@ -1579,11 +1582,10 @@ static int fastrpc_device_open(struct inode *inode, struct file *filp)
 	INIT_LIST_HEAD(&fl->maps);
 	INIT_LIST_HEAD(&fl->mmaps);
 	INIT_LIST_HEAD(&fl->user);
-	fl->tgid = current->tgid;
 	fl->cctx = cctx;
 	fl->is_secure_dev = fdevice->secure;
 
-	fl->sctx = fastrpc_session_alloc(cctx);
+	fl->sctx = fastrpc_session_alloc(fl);
 	if (!fl->sctx) {
 		dev_err(&cctx->rpdev->dev, "No session available\n");
 		mutex_destroy(&fl->mutex);
@@ -1647,7 +1649,7 @@ static int fastrpc_dmabuf_alloc(struct fastrpc_user *fl, char __user *argp)
 static int fastrpc_init_attach(struct fastrpc_user *fl, int pd)
 {
 	struct fastrpc_invoke_args args[1];
-	int tgid = fl->tgid;
+	int tgid = fl->client_id;
 	u32 sc;
 
 	args[0].ptr = (u64)(uintptr_t) &tgid;
@@ -1803,7 +1805,7 @@ static int fastrpc_req_munmap_impl(struct fastrpc_user *fl, struct fastrpc_buf *
 	int err;
 	u32 sc;
 
-	req_msg.pgid = fl->tgid;
+	req_msg.pgid = fl->client_id;
 	req_msg.size = buf->size;
 	req_msg.vaddr = buf->raddr;
 
@@ -1889,7 +1891,7 @@ static int fastrpc_req_mmap(struct fastrpc_user *fl, char __user *argp)
 		return err;
 	}
 
-	req_msg.pgid = fl->tgid;
+	req_msg.pgid = fl->client_id;
 	req_msg.flags = req.flags;
 	req_msg.vaddr = req.vaddrin;
 	req_msg.num = sizeof(pages);
@@ -1978,7 +1980,7 @@ static int fastrpc_req_mem_unmap_impl(struct fastrpc_user *fl, struct fastrpc_me
 		return -EINVAL;
 	}
 
-	req_msg.pgid = fl->tgid;
+	req_msg.pgid = fl->client_id;
 	req_msg.len = map->len;
 	req_msg.vaddrin = map->raddr;
 	req_msg.fd = map->fd;
@@ -2031,7 +2033,7 @@ static int fastrpc_req_mem_map(struct fastrpc_user *fl, char __user *argp)
 		return err;
 	}
 
-	req_msg.pgid = fl->tgid;
+	req_msg.pgid = fl->client_id;
 	req_msg.fd = req.fd;
 	req_msg.offset = req.offset;
 	req_msg.vaddrin = req.vaddrin;