netdev - Re: [PATCH v2 03/15] net: rnpgbe: Add basic mbx ops support

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Message-ID: <e66591a1-0ffa-4135-9347-52dc7745728f@lunn.ch>
Date: Mon, 21 Jul 2025 17:43:41 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Dong Yibo <dong100@...se.com>
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,
	netdev@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 03/15] net: rnpgbe: Add basic mbx ops support

>  #define MAX_VF_NUM (8)

> +	hw->max_vfs = 7;

???


>  }
>  
>  /**
> @@ -117,6 +119,7 @@ static void rnpgbe_get_invariants_n210(struct mucse_hw *hw)
>  	/* update hw feature */
>  	hw->feature_flags |= M_HW_FEATURE_EEE;
>  	hw->usecstocount = 62;
> +	hw->max_vfs_noari = 7;

???

> +int mucse_read_mbx(struct mucse_hw *hw, u32 *msg, u16 size,
> +		   enum MBX_ID mbx_id)
> +{
> +	struct mucse_mbx_info *mbx = &hw->mbx;
> +
> +	/* limit read to size of mailbox */
> +	if (size > mbx->size)
> +		size = mbx->size;
> +
> +	if (!mbx->ops.read)
> +		return -EIO;

How would that happen?

> +
> +	return mbx->ops.read(hw, msg, size, mbx_id);

> +int mucse_write_mbx(struct mucse_hw *hw, u32 *msg, u16 size,
> +		    enum MBX_ID mbx_id)
> +{
> +	struct mucse_mbx_info *mbx = &hw->mbx;
> +
> +	if (size > mbx->size)
> +		return -EINVAL;
> +
> +	if (!mbx->ops.write)
> +		return -EIO;

How would either of these two conditions happen.

> +static u16 mucse_mbx_get_req(struct mucse_hw *hw, int reg)
> +{
> +	/* force memory barrier */
> +	mb();
> +	return ioread32(hw->hw_addr + reg) & GENMASK(15, 0);

I'm no expert on memory barriers, but what are you trying to achieve
here? Probably the most used pattern of an mb() is to flush out writes
to hardware before doing a special write which triggers the hardware
to do something. That is not what is happening here.

> +static void mucse_mbx_inc_pf_req(struct mucse_hw *hw,
> +				 enum MBX_ID mbx_id)
> +{
> +	struct mucse_mbx_info *mbx = &hw->mbx;
> +	u32 reg, v;
> +	u16 req;
> +
> +	reg = (mbx_id == MBX_FW) ? PF2FW_COUNTER(mbx) :
> +				   PF2VF_COUNTER(mbx, mbx_id);
> +	v = mbx_rd32(hw, reg);
> +	req = (v & GENMASK(15, 0));
> +	req++;
> +	v &= GENMASK(31, 16);
> +	v |= req;
> +	/* force before write to hw */
> +	mb();
> +	mbx_wr32(hw, reg, v);
> +	/* update stats */
> +	hw->mbx.stats.msgs_tx++;

What are you forcing? As i said, i'm no expert on memory barriers, but
to me, it looks like whoever wrote this code also does not understand
memory barriers.

> +static int mucse_obtain_mbx_lock_pf(struct mucse_hw *hw, enum MBX_ID mbx_id)
> +{
> +	struct mucse_mbx_info *mbx = &hw->mbx;
> +	int try_cnt = 5000, ret;
> +	u32 reg;
> +
> +	reg = (mbx_id == MBX_FW) ? PF2FW_MBOX_CTRL(mbx) :
> +				   PF2VF_MBOX_CTRL(mbx, mbx_id);
> +	while (try_cnt-- > 0) {
> +		/* Take ownership of the buffer */
> +		mbx_wr32(hw, reg, MBOX_PF_HOLD);
> +		/* force write back before check */
> +		wmb();
> +		if (mbx_rd32(hw, reg) & MBOX_PF_HOLD)
> +			return 0;
> +		udelay(100);
> +	}
> +	return ret;

I've not compiled this, but isn't ret uninitialized here? I would also
expect it to return -ETIMEDOUT?

	Andrew