linux-kernel - [PATCH] drivers/serial/sunzilog: Interrupt enable before ISR handler installed

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Message-ID: <Pine.LNX.4.61.0705091858490.29173@mtfhpc.demon.co.uk>
Date:	Wed, 9 May 2007 19:17:29 +0100 (BST)
From:	Mark Fortescue <mark@...hpc.demon.co.uk>
To:	David Miller <davem@...emloft.net>
cc:	wli@...omorphy.com, linux-kernel@...r.kernel.org,
	sparclinux@...r.kernel.org, linux-serial@...r.kernel.org
Subject: [PATCH] drivers/serial/sunzilog: Interrupt enable before ISR handler
 installed

Hi all,

I have added a from line, comment and signed-off-by line to the attached 
patch file.

Regards
 	Mark Fortescue.

On Mon, 7 May 2007, David Miller wrote:

Regards
 	Mark Fortescue.

> From: Mark Fortescue <mark@...hpc.demon.co.uk>
> Date: Sun, 29 Apr 2007 23:00:29 +0100 (BST)
>
>> I have altered the patch as advised and I have attached it to prevent my
>> email client from making a mess of it.
>>
>> The attached patch changes the interrupt enable sequence for the sunzilog
>> driver so that interrupts are not enabled untill after the interrupt
>> handler has been installed. If this is not done, some SS1 and SS2 sun4c
>> systems panic on un-handled interrupt before the handler gets installed
>> preventing boot.
>>
>> It also adds in support for the ESCC version of the zilog chips. The ESCC
>> detection works but the FIFO enable may cause issues with modem and
>> receive character status. My interpretation of the SCC manual and the code
>> is that it sould be OK.
>
> Your patch looks good, thanks for working on this.  As other's
> have mentioned you should provide a proper "Signed-off-by: "
> line with your patch changelog as describe in
> linux/Documentation/SubmittingPatches.
>
> I wonder if there is a way to get rid of all of that MIE twiddling
> logic during the probe.
>
> The chicken-and-egg problem in this driver is that we need to get
> all the chips mostly functional before we let the IRQ handler get
> at the chips in the sunzilog_irq_chain.  That list is setup very
> early, so it isn't a datastructure problem.
>
> One thing we could do is check in the IRQ handler is skip chips
> which don't have their registers mapped yet.
>
> But that'd put silly logic in the fast path of this driver, whereas
> your solution does all of this out-of-line.  So your patch is
> probably the best.
>
> Please resubmit with the proper "Signed-off-by: " line and I will
> apply your patch, thanks!
>
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View attachment "sunzilog.patch" of type "TEXT/PLAIN" (12074 bytes)