netdev - Re: [PATCH net-next v4 08/13] net: wwan: t7xx: Add data path interface

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Date:   Thu, 3 Feb 2022 16:23:49 +0200 (EET)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     Ricardo Martinez <ricardo.martinez@...ux.intel.com>
cc:     Netdev <netdev@...r.kernel.org>, linux-wireless@...r.kernel.org,
        kuba@...nel.org, davem@...emloft.net, johannes@...solutions.net,
        ryazanov.s.a@...il.com, loic.poulain@...aro.org,
        m.chetan.kumar@...el.com, chandrashekar.devegowda@...el.com,
        linuxwwan@...el.com, chiranjeevi.rapolu@...ux.intel.com,
        haijun.liu@...iatek.com, amir.hanania@...el.com,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        dinesh.sharma@...el.com, eliot.lee@...el.com,
        moises.veleta@...el.com, pierre-louis.bossart@...el.com,
        muralidharan.sethuraman@...el.com, Soumya.Prakash.Mishra@...el.com,
        sreehari.kancharla@...el.com
Subject: Re: [PATCH net-next v4 08/13] net: wwan: t7xx: Add data path
 interface

On Thu, 13 Jan 2022, Ricardo Martinez wrote:

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

> +	unsigned short		last_ch_id;
Values is never used.

> +	if (old_rl_idx > old_wr_idx && new_wr_idx >= old_rl_idx) {
> +		dev_err(dpmaif_ctrl->dev, "RX BAT flow check fail\n");
> +		return -EINVAL;
> +	}
> +
> +	if (new_wr_idx >= bat_req->bat_size_cnt) {
> +		new_wr_idx -= bat_req->bat_size_cnt;
> +		if (new_wr_idx >= old_rl_idx) {
> +			dev_err(dpmaif_ctrl->dev, "RX BAT flow check fail\n");
> +			return -EINVAL;
> +		}

Make a label for the identical block and goto there.

> +static void t7xx_unmap_bat_skb(struct device *dev, struct dpmaif_bat_skb *bat_skb_base,
> +			       unsigned int index)
> +{
> +	struct dpmaif_bat_skb *bat_skb = bat_skb_base + index;
> +
> +	if (bat_skb->skb) {
> +		dma_unmap_single(dev, bat_skb->data_bus_addr, bat_skb->data_len, DMA_FROM_DEVICE);
> +		kfree_skb(bat_skb->skb);

For consistency, dev_kfree_skb?

> + * @initial: Indicates if the ring is being populated for the first time.
> + *
> + * Allocate skb and store the start address of the data buffer into the BAT ring.
> + * If this is not the initial call, notify the HW about the new entries.
> + *
> + * Return:
> + * * 0		- Success.
> + * * -ERROR	- Error code from failure sub-initializations.
> + */
> +int t7xx_dpmaif_rx_buf_alloc(struct dpmaif_ctrl *dpmaif_ctrl,
> +			     const struct dpmaif_bat_request *bat_req,
> +			     const unsigned char q_num, const unsigned int buf_cnt,
> +			     const bool initial)

vs its prototype:

+int t7xx_dpmaif_rx_buf_alloc(struct dpmaif_ctrl *dpmaif_ctrl,
+                            const struct dpmaif_bat_request *bat_req, const unsigned char q_num,
+                            const unsigned int buf_cnt, const bool first_time);

> +int t7xx_dpmaif_rx_frag_alloc(struct dpmaif_ctrl *dpmaif_ctrl, struct dpmaif_bat_request *bat_req,
> +			      const unsigned int buf_cnt, const bool initial)
> +{
> +	struct dpmaif_bat_page *bat_skb = bat_req->bat_skb;
> +	unsigned short cur_bat_idx = bat_req->bat_wr_idx;
> +	unsigned int buf_space;
> +	int ret, i;
...
> +	ret = i < buf_cnt ? -ENOMEM : 0;
> +	if (ret && initial) {

int ret = 0, i;
...
if (i < buf_cnt) {
	ret = -ENOMEM;
	if (initial) {
		...
	}
}

> +	if (!tx_drb_available || txq->tx_submit_skb_cnt >= txq->tx_list_max_len) {
> +		cb = dpmaif_ctrl->callbacks;
> +		cb->state_notify(dpmaif_ctrl->t7xx_dev, DMPAIF_TXQ_STATE_FULL, txqt);
> +		return -EBUSY;
> +	}
> +
> +	skb->cb[TX_CB_QTYPE] = txqt;
> +	skb->cb[TX_CB_DRB_CNT] = send_drb_cnt;
> +
> +	spin_lock_irqsave(&txq->tx_skb_lock, flags);
> +	list_add_tail(&skb->list, &txq->tx_skb_queue);
> +	txq->tx_submit_skb_cnt++;
> +	spin_unlock_irqrestore(&txq->tx_skb_lock, flags);

Perhaps the critical section needs to start earlier to enforce that 
tx_list_max_len check?


(I'm yet to read half of this patch...)

-- 
 i.