On 4/4/2022 4:50 PM, Sergey Ryazanov wrote:
Hello Ricardo,
On Tue, Apr 5, 2022 at 2:29 AM Martinez, Ricardo
<ricardo.martinez@xxxxxxxxxxxxxxx> wrote:
On 3/6/2022 6:58 PM, Sergey Ryazanov wrote:
On Thu, Feb 24, 2022 at 1:35 AM Ricardo Martinez
<ricardo.martinez@xxxxxxxxxxxxxxx> wrote:
From: Haijun Liu <haijun.liu@xxxxxxxxxxxx>
Data Path Modem AP Interface (DPMAIF) HIF layer provides methods
for initialization, ISR, control and event handling of TX/RX flows.
DPMAIF TX
Exposes the `dmpaif_tx_send_skb` function which can be used by the
network device to transmit packets.
The uplink data management uses a Descriptor Ring Buffer (DRB).
First DRB entry is a message type that will be followed by 1 or more
normal DRB entries. Message type DRB will hold the skb information
and each normal DRB entry holds a pointer to the skb payload.
DPMAIF RX
The downlink buffer management uses Buffer Address Table (BAT) and
Packet Information Table (PIT) rings.
The BAT ring holds the address of skb data buffer for the HW to use,
while the PIT contains metadata about a whole network packet including
a reference to the BAT entry holding the data buffer address.
The driver reads the PIT and BAT entries written by the modem, when
reaching a threshold, the driver will reload the PIT and BAT rings.
...
+static int t7xx_dpmaif_add_skb_to_ring(struct dpmaif_ctrl *dpmaif_ctrl, struct sk_buff *skb)
+{
+ unsigned short cur_idx, drb_wr_idx_backup;
...
+ txq = &dpmaif_ctrl->txq[skb_cb->txq_number];
...
+ cur_idx = txq->drb_wr_idx;
+ drb_wr_idx_backup = cur_idx;
...
+ for (wr_cnt = 0; wr_cnt < payload_cnt; wr_cnt++) {
...
+ bus_addr = dma_map_single(dpmaif_ctrl->dev, data_addr, data_len, DMA_TO_DEVICE);
+ if (dma_mapping_error(dpmaif_ctrl->dev, bus_addr)) {
+ dev_err(dpmaif_ctrl->dev, "DMA mapping fail\n");
+ atomic_set(&txq->tx_processing, 0);
+
+ spin_lock_irqsave(&txq->tx_lock, flags);
+ txq->drb_wr_idx = drb_wr_idx_backup;
+ spin_unlock_irqrestore(&txq->tx_lock, flags);
What is the purpose of locking here?
The intention is to protect against concurrent access of drb_wr_idx by t7xx_txq_drb_wr_available()
t7xx_txq_drb_wr_available() only reads the drb_wr_idx field, why would
you serialize that concurrent read?
Good point, drb_wr_idx has only 1 writer which is this thread.
+ return -ENOMEM;
+ }
...
+ }
...
+}
