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

On Thu, Sep 04, 2025 at 02:05:57PM +0200, Andrew Lunn wrote:

On Thu, Sep 04, 2025 at 11:19:48AM +0800, Yibo Dong wrote:

quoted

On Thu, Sep 04, 2025 at 12:24:17AM +0200, Andrew Lunn wrote:

quoted

quoted

 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;

quoted

+/**
+ * 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);

As i said, functions like this come in pairs. obtain/release,
lock/unlock. When reading code, you want to be able to see both of the
pair in a function, to know the unlock is not missing. The kernel even
has tools which will validate all paths through a function releasing
locks. Often error paths get this wrong.

So please make this a function, give it a name which makes it obvious
it is the opposite of mucse_obtain_mbx_lock_pf().

	Andrew

Got it, I will update this.

Thanks for your feedback.