linux-kernel - Re: [PATCH 1/3] cyber2000fb: fix machine hang on module load

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4C5493DD.7010402@garzik.org>
Date:	Sat, 31 Jul 2010 17:21:33 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	Ondrej Zary <linux@...nbow-software.org>
CC:	Russell King - ARM Linux <linux@....linux.org.uk>,
	linux-fbdev@...r.kernel.org,
	Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] cyber2000fb: fix machine hang on module load

On 07/31/2010 04:55 PM, Ondrej Zary wrote:
> I was testing two CyberPro 2000 based PCI cards on x86 and the machine always
> hanged completely when the cyber2000fb module was loaded. It seems that the
> card hangs when some registers are accessed too quickly after writing RAMDAC
> control register. With this patch, both card work.
>
> Add delay after RAMDAC control register write to prevent hangs on module load.
>
> Signed-off-by: Ondrej Zary<linux@...nbow-software.org>
>
> --- linux-2.6.35-rc2-orig/drivers/video/cyber2000fb.c	2010-06-06 05:43:24.000000000 +0200
> +++ linux-2.6.35-rc3/drivers/video/cyber2000fb.c	2010-07-27 23:12:37.000000000 +0200
> @@ -436,6 +436,8 @@ static void cyber2000fb_write_ramdac_ctr
>   	cyber2000fb_writeb(i | 4, 0x3cf, cfb);
>   	cyber2000fb_writeb(val, 0x3c6, cfb);
>   	cyber2000fb_writeb(i, 0x3cf, cfb);
> +	/* prevent card lock-up observed on x86 with CyberPro 2000 */
> +	cyber2000fb_readb(0x3cf, cfb);
>   }

IIRC, cyber2000 is basically an S3 graphics chip.  When working on s3fb, 
over a decade ago, ISTR needing a lot of MMIO register flushes -- dummy 
register reads -- to flush out just-written register writes.


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/