linux-kernel - Re: [PATCH net-next v1] net: microchip: lan743x: Reduce PTP timeout on HW failure

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Message-ID: <01145749-30a7-47a3-a5e6-03f4d0ee1264@lunn.ch>
Date: Tue, 7 May 2024 03:33:01 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Rengarajan S <rengarajan.s@...rochip.com>
Cc: bryan.whitehead@...rochip.com, UNGLinuxDriver@...rochip.com,
	davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
	pabeni@...hat.com, richardcochran@...il.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v1] net: microchip: lan743x: Reduce PTP timeout
 on HW failure

On Thu, May 02, 2024 at 10:33:00AM +0530, Rengarajan S wrote:
> The PTP_CMD_CTL is a self clearing register which controls the PTP clock
> values. In the current implementation driver waits for a duration of 20
> sec in case of HW failure to clear the PTP_CMD_CTL register bit. This
> timeout of 20 sec is very long to recognize a HW failure, as it is
> typically cleared in one clock(<16ns). Hence reducing the timeout to 1 sec
> would be sufficient to conclude if there is any HW failure observed. The
> usleep_range will sleep somewhere between 1 msec to 20 msec for each
> iteration. By setting the PTP_CMD_CTL_TIMEOUT_CNT to 50 the max timeout
> is extended to 1 sec.

This patch has already been merged, so this is just for my
curiosity. The hardware is dead. Does it really matter if we wait 1s
or 20 seconds. It is still dead? This is a void function. Other than
reporting that the hardware is dead, nothing is done. So this change
seems pointless?

	Andrew