netdev - Re: [PATCH net-next v4 02/13] net: wwan: t7xx: Add control DMA interface

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Date:   Tue, 18 Jan 2022 14:22:08 -0800
From:   "Martinez, Ricardo" <ricardo.martinez@...ux.intel.com>
To:     Ilpo Järvinen <ilpo.jarvinen@...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 02/13] net: wwan: t7xx: Add control DMA
 interface


On 1/18/2022 6:13 AM, Ilpo Järvinen wrote:
> On Thu, 13 Jan 2022, Ricardo Martinez wrote:
...
>> +#define CLDMA_NUM 2
> I tried to understand its purpose but it seems that only one of the
> indexes is used in the arrays where this define gives the size? Related to
> this, ID_CLDMA0 is not used anywhere?

The modem HW has 2 CLDMAs, idx 0 for the app processor (SAP) and idx 1 
for the modem (MD).

CLDMA_NUM is defined as 2 to reflect the HW capabilities but mainly to 
have a cleaner upcoming

patches, which will use ID_CLDMA0.

If having array's of size 1 is not a problem then we can define 
CLDMA_NUM as 1 and

play with the CLDMA indexes.

...


>> +static void t7xx_cldma_enable_irq(struct cldma_ctrl *md_ctrl)
>> +{
>> +	t7xx_pcie_mac_set_int(md_ctrl->t7xx_dev, md_ctrl->hw_info.phy_interrupt_id);
>> +}
>> +
>> +static void t7xx_cldma_disable_irq(struct cldma_ctrl *md_ctrl)
>> +{
>> +	t7xx_pcie_mac_clear_int(md_ctrl->t7xx_dev, md_ctrl->hw_info.phy_interrupt_id);
>> +}
> t7xx_pcie_mac_set_int and t7xx_pcie_mac_clear_int are only defined
> by a later patch.
>
>> +static bool t7xx_cldma_qs_are_active(struct t7xx_cldma_hw *hw_info)
>> +{
>> +	unsigned int tx_active;
>> +	unsigned int rx_active;
>> +
>> +	tx_active = t7xx_cldma_hw_queue_status(hw_info, CLDMA_ALL_Q, MTK_TX);
>> +	rx_active = t7xx_cldma_hw_queue_status(hw_info, CLDMA_ALL_Q, MTK_RX);
>> +	if (tx_active == CLDMA_INVALID_STATUS || rx_active == CLDMA_INVALID_STATUS)
> These cannot ever be true because of mask in t7xx_cldma_hw_queue_status().

t7xx_cldma_hw_queue_status() shouldn't apply the mask for CLDMA_ALL_Q.

>> +static int t7xx_cldma_clear_rxq(struct cldma_ctrl *md_ctrl, int qnum)
>> +{
>> +	struct cldma_queue *rxq = &md_ctrl->rxq[qnum];
>> +	struct cldma_request *req;
>> +	struct cldma_rgpd *rgpd;
>> +	unsigned long flags;
>> +
>> +	spin_lock_irqsave(&rxq->ring_lock, flags);
>> +	t7xx_cldma_q_reset(rxq);
>> +	list_for_each_entry(req, &rxq->tr_ring->gpd_ring, entry) {
>> +		rgpd = req->gpd;
>> +		rgpd->gpd_flags = GPD_FLAGS_IOC | GPD_FLAGS_HWO;
>> +		rgpd->data_buff_len = 0;
>> +
>> +		if (req->skb) {
>> +			req->skb->len = 0;
>> +			skb_reset_tail_pointer(req->skb);
>> +		}
>> +	}
>> +
>> +	spin_unlock_irqrestore(&rxq->ring_lock, flags);
>> +	list_for_each_entry(req, &rxq->tr_ring->gpd_ring, entry) {
>> +		int ret;
> I find this kind of newline+unlock+more code a bit odd groupingwise.
> IMO, the newline should be after the unlock rather than just before it to
> better indicate the critical sections visually.

Agree. In general, the driver uses a newline after '}', unlock 
operations should be an

exception since it looks better to keep the critical section blocks 
together.

...

>> +/**
>> + * t7xx_cldma_send_skb() - Send control data to modem.
>> + * @md_ctrl: CLDMA context structure.
>> + * @qno: Queue number.
>> + * @skb: Socket buffer.
>> + * @blocking: True for blocking operation.
>> + *
>> + * Send control packet to modem using a ring buffer.
>> + * If blocking is set, it will wait for completion.
>> + *
>> + * Return:
>> + * * 0		- Success.
>> + * * -ENOMEM	- Allocation failure.
>> + * * -EINVAL	- Invalid queue request.
>> + * * -EBUSY	- Resource lock failure.
>> + */
>> +int t7xx_cldma_send_skb(struct cldma_ctrl *md_ctrl, int qno, struct sk_buff *skb, bool blocking)
>> +{
>> +	struct cldma_request *tx_req;
>> +	struct cldma_queue *queue;
>> +	unsigned long flags;
>> +	int ret;
>> +
>> +	if (qno >= CLDMA_TXQ_NUM)
>> +		return -EINVAL;
>> +
>> +	queue = &md_ctrl->txq[qno];
>> +
>> +	spin_lock_irqsave(&md_ctrl->cldma_lock, flags);
>> +	if (!(md_ctrl->txq_active & BIT(qno))) {
>> +		ret = -EBUSY;
>> +		spin_unlock_irqrestore(&md_ctrl->cldma_lock, flags);
>> +		goto allow_sleep;
>> +	}
> ...
>> +		if (!blocking) {
>> +			ret = -EBUSY;
>> +			break;
>> +		}
>> +
>> +		ret = wait_event_interruptible_exclusive(queue->req_wq, queue->budget > 0);
>> +	} while (!ret);
>> +
>> +allow_sleep:
>> +	return ret;
>> +}
> First of all, if I interpreted the call chains correctly, this function is
> always called with blocking=true.
>
> Second, the first codepath returning -EBUSY when not txq_active seems
> twisted/reversed logic to me (not active => busy ?!?).

What about -EINVAL?

Other codes considered: -EPERM, -ENETDOWN.

>
...