cyber2000fb: fix machine hang on module load

Ondrej Zary · Russell King · commit 00b4703f03ce · 2010-07-30T23:29:33.000+01:00
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 &lt;linux@rainbow-software.org&gt;
Signed-off-by: Russell King &lt;rmk+kernel@arm.linux.org.uk&gt;
diff --git a/drivers/video/cyber2000fb.c b/drivers/video/cyber2000fb.c
@@ -436,6 +436,8 @@ static void cyber2000fb_write_ramdac_ctrl(struct cfb_info *cfb)
 	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);
 }
 
 static void cyber2000fb_set_timing(struct cfb_info *cfb, struct par_info *hw)

Original file line number	Diff line number	Diff line change
`@@ -436,6 +436,8 @@ static void cyber2000fb_write_ramdac_ctrl(struct cfb_info *cfb)`
`436`	`436`	`cyber2000fb_writeb(i \| 4, 0x3cf, cfb);`
`437`	`437`	`cyber2000fb_writeb(val, 0x3c6, cfb);`
`438`	`438`	`cyber2000fb_writeb(i, 0x3cf, cfb);`
	`439`	`+ /* prevent card lock-up observed on x86 with CyberPro 2000 */`
	`440`	`+ cyber2000fb_readb(0x3cf, cfb);`
`439`	`441`	`}`
`440`	`442`
`441`	`443`	`static void cyber2000fb_set_timing(struct cfb_info cfb, struct par_info hw)`