On Mon, 6 Dec 2021, Ricardo Martinez wrote:

From: Haijun Liu <haijun.liu@mediatek.com>

Cross Layer DMA (CLDMA) Hardware interface (HIF) enables the control
path of Host-Modem data transfers. CLDMA HIF layer provides a common
interface to the Port Layer.

CLDMA manages 8 independent RX/TX physical channels with data flow
control in HW queues. CLDMA uses ring buffers of General Packet
Descriptors (GPD) for TX/RX. GPDs can represent multiple or single
data buffers (DB).

CLDMA HIF initializes GPD rings, registers ISR handlers for CLDMA
interrupts, and initializes CLDMA HW registers.

CLDMA TX flow:
1. Port Layer write
2. Get DB address
3. Configure GPD
4. Triggering processing via HW register write

CLDMA RX flow:
1. CLDMA HW sends a RX "done" to host
2. Driver starts thread to safely read GPD
3. DB is sent to Port layer
4. Create a new buffer for GPD ring

Signed-off-by: Haijun Liu <haijun.liu@mediatek.com>
Signed-off-by: Chandrashekar Devegowda <chandrashekar.devegowda@intel.com>
Co-developed-by: Ricardo Martinez <ricardo.martinez@linux.intel.com>
Signed-off-by: Ricardo Martinez <ricardo.martinez@linux.intel.com>

+static struct cldma_request *t7xx_cldma_ring_step_forward(struct cldma_ring *ring,
+							  struct cldma_request *req)
+{
+	if (req->entry.next == &ring->gpd_ring)
+		return list_first_entry(&ring->gpd_ring, struct cldma_request, entry);
+
+	return list_next_entry(req, entry);
+}
+
+static struct cldma_request *t7xx_cldma_ring_step_backward(struct cldma_ring *ring,
+							   struct cldma_request *req)
+{
+	if (req->entry.prev == &ring->gpd_ring)
+		return list_last_entry(&ring->gpd_ring, struct cldma_request, entry);
+
+	return list_prev_entry(req, entry);
+}

Wouldn't these two seems generic enough to warrant adding something like 
list_next/prev_entry_circular(...) to list.h?

+static int t7xx_cldma_alloc_and_map_skb(struct cldma_ctrl *md_ctrl, struct cldma_request *req,
+					size_t size)
+{
+	req->skb = __dev_alloc_skb(size, GFP_KERNEL);
+	if (!req->skb)
+		return -ENOMEM;
+
+	req->mapped_buff = dma_map_single(md_ctrl->dev, req->skb->data,
+					  t7xx_skb_data_size(req->skb), DMA_FROM_DEVICE);

t7xx_skb_data_size() is not defined by this patch but only in a later 
patch in the series.

Also, I'd prefer its name to be changed to e.g. t7xx_skb_data_area_size() 
given what it calculates. IHMO, "data size" refers to actual 
frame/packet/payload and does not include the reserves/*rooms around it
so the name is bit misleading as is.


-- 
 i.