netdev - Re: [PATCH net-next v10 3/5] net: rnpgbe: Add basic mbx ops support

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Message-ID: <AF92025D9CBFCF3B+20250904031948.GA1022066@nic-Precision-5820-Tower>
Date: Thu, 4 Sep 2025 11:19:48 +0800
From: Yibo Dong <dong100@...se.com>
To: Andrew Lunn <andrew@...n.ch>
Cc: andrew+netdev@...n.ch, davem@...emloft.net, edumazet@...gle.com,
	kuba@...nel.org, pabeni@...hat.com, horms@...nel.org,
	corbet@....net, gur.stavi@...wei.com, maddy@...ux.ibm.com,
	mpe@...erman.id.au, danishanwar@...com, lee@...ger.us,
	gongfan1@...wei.com, lorenzo@...nel.org, geert+renesas@...der.be,
	Parthiban.Veerasooran@...rochip.com, lukas.bulwahn@...hat.com,
	alexanderduyck@...com, richardcochran@...il.com, kees@...nel.org,
	gustavoars@...nel.org, rdunlap@...radead.org,
	vadim.fedorenko@...ux.dev, netdev@...r.kernel.org,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH net-next v10 3/5] net: rnpgbe: Add basic mbx ops support

On Thu, Sep 04, 2025 at 12:24:17AM +0200, Andrew Lunn wrote:
> >  struct mucse_mbx_info {
> > +	struct mucse_mbx_stats stats;
> > +	u32 timeout;
> > +	u32 usec_delay;
> > +	u16 size;
> > +	u16 fw_req;
> > +	u16 fw_ack;
> > +	/* lock for only one use mbx */
> > +	struct mutex lock;
> >  	/* fw <--> pf mbx */
> >  	u32 fw_pf_shm_base;
> >  	u32 pf2fw_mbox_ctrl;
> 
> > +/**
> > + * mucse_obtain_mbx_lock_pf - Obtain mailbox lock
> > + * @hw: pointer to the HW structure
> > + *
> > + * This function maybe used in an irq handler.
> > + *
> > + * Return: 0 if we obtained the mailbox lock or else -EIO
> > + **/
> > +static int mucse_obtain_mbx_lock_pf(struct mucse_hw *hw)
> > +{
> > +	struct mucse_mbx_info *mbx = &hw->mbx;
> > +	int try_cnt = 5000;
> > +	u32 reg;
> > +
> > +	reg = PF2FW_MBOX_CTRL(mbx);
> > +	while (try_cnt-- > 0) {
> > +		mbx_ctrl_wr32(mbx, reg, MBOX_PF_HOLD);
> > +		/* force write back before check */
> > +		wmb();
> > +		if (mbx_ctrl_rd32(mbx, reg) & MBOX_PF_HOLD)
> > +			return 0;
> > +		udelay(100);
> > +	}
> > +	return -EIO;
> > +}
> 
> If there is a function which obtains a lock, there is normally a
> function which releases a lock. But i don't see it.
> 

The lock is relased when send MBOX_CTRL_REQ in mucse_write_mbx_pf:

mbx_ctrl_wr32(mbx, ctrl_reg, MBOX_CTRL_REQ);

Set MBOX_PF_HOLD(bit3) to hold the lock, clear bit3 to release, and set
MBOX_CTRL_REQ(bit0) to send the req. req and lock are different bits in
one register. So we send the req along with releasing lock (set bit0 and
clear bit3).
Maybe I should add comment like this?

/* send the req along with releasing the lock */
mbx_ctrl_wr32(mbx, ctrl_reg, MBOX_CTRL_REQ);

> > +void mucse_init_mbx_params_pf(struct mucse_hw *hw)
> > +{
> > +	struct mucse_mbx_info *mbx = &hw->mbx;
> > +
> > +	mbx->usec_delay = 100;
> > +	mbx->timeout = (4 * USEC_PER_SEC) / mbx->usec_delay;
> > +	mbx->stats.msgs_tx = 0;
> > +	mbx->stats.msgs_rx = 0;
> > +	mbx->stats.reqs = 0;
> > +	mbx->stats.acks = 0;
> > +	mbx->size = MUCSE_MAILBOX_BYTES;
> > +	mutex_init(&mbx->lock);
> 
> And this mutex never seems to be used anywhere. What is it supposed to
> be protecting?
> 

mbx->lock is used in patch5, to ensure that only one uses mbx.
I will move it to patch5.

>     Andrew
> 
> ---
> pw-bot: cr
> 

Thanks for your feedback.