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From: Finn Thain <fthain@telegraphics.com.au>
To: Guenter Roeck <linux@roeck-us.net>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Joshua Thompson <funaho@jurai.org>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	linux-m68k@lists.linux-m68k.org,
	Laurent Vivier <lvivier@redhat.com>,
	Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>,
	linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/9] macintosh/via-macii: Poll the device most likely to respond
Date: Mon, 10 Aug 2020 08:58:43 +1000 (AEST)
Message-ID: <alpine.LNX.2.23.453.2008100844450.8@nippy.intranet> (raw)
In-Reply-To: <20200809185541.GA133779@roeck-us.net>

On Sun, 9 Aug 2020, Guenter Roeck wrote:

> Hi,
> 
> On Sun, Jun 28, 2020 at 02:23:12PM +1000, Finn Thain wrote:
> > Poll the most recently polled device by default, rather than the lowest
> > device address that happens to be enabled in autopoll_devs. This improves
> > input latency. Re-use macii_queue_poll() rather than duplicate that logic.
> > This eliminates a static struct and function.
> > 
> > Fixes: d95fd5fce88f0 ("m68k: Mac II ADB fixes") # v5.0+
> > Tested-by: Stan Johnson <userm57@yahoo.com>
> > Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
> 
> With this patch applied, the qemu "q800" emulation no longer works and 
> is stuck in early boot. Any idea why that might be the case, and/or how 
> to debug it ?
> 

The problem you're seeing was mentioned in the cover letter,
https://lore.kernel.org/linux-m68k/cover.1593318192.git.fthain@telegraphics.com.au/

Since this series was merged, Linus' tree is no longer compatible with 
long-standing QEMU bugs.

The best way to fix this is to upgrade QEMU (latest is 5.1.0-rc3). Or use 
the serial console instead of the framebuffer console.

I regret the inconvenience but the alternative was worse: adding code to 
Linux to get compatibility with QEMU bugs (which were added to QEMU due to 
Linux bugs).

My main concern is correct operation on actual hardware, as always. But 
some QEMU developers are working on support for operating systems besides 
Linux.

Therefore, I believe that both QEMU and Linux should aim for compatibility 
with actual hardware and not bug compatibility with each other.

  reply index

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-28  4:23 [PATCH 0/9] Macintosh II ADB driver fixes Finn Thain
2020-06-28  4:23 ` [PATCH 2/9] macintosh/via-macii: Poll the device most likely to respond Finn Thain
2020-08-09 18:55   ` Guenter Roeck
2020-08-09 22:58     ` Finn Thain [this message]
2020-08-10  1:16       ` Guenter Roeck
2020-06-28  4:23 ` [PATCH 7/9] macintosh/via-macii: Use unsigned type for autopoll_devs variable Finn Thain
2020-06-28  4:23 ` [PATCH 6/9] macintosh/via-macii: Use bool type for reading_reply variable Finn Thain
2020-06-28  4:23 ` [PATCH 1/9] macintosh/via-macii: Access autopoll_devs when inside lock Finn Thain
2020-08-09 19:01   ` Guenter Roeck
2020-08-09 23:15     ` Finn Thain
2020-06-28  4:23 ` [PATCH 9/9] macintosh/via-macii: Clarify definition of macii_init() Finn Thain
2020-06-28  4:23 ` [PATCH 5/9] macintosh/via-macii: Handle poll replies correctly Finn Thain
2020-06-28  4:23 ` [PATCH 4/9] macintosh/via-macii: Remove read_done state Finn Thain
2020-06-28  4:23 ` [PATCH 3/9] macintosh/via-macii: Handle /CTLR_IRQ signal correctly Finn Thain
2020-06-28  4:23 ` [PATCH 8/9] macintosh/via-macii: Use the stack for reset request storage Finn Thain
2020-07-27  7:26 ` [PATCH 0/9] Macintosh II ADB driver fixes Michael Ellerman

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