Re: [patch 2.6] don't put IDE disks in standby mode on halt on Alpha

[Ivan Kokshaysky <ink@jurassic.park.msu.ru>]

On Fri, May 28, 2004 at 05:40:50PM +0200, Bartlomiej Zolnierkiewicz wrote:
> - AFAIR there are some buggy disks having flush cache
>   bits that need standby anyway

Oh horror. I wouldn't be surprised if some drives don't flush
the cache even on standby...

> - you will hit 'halt problem' on alpha if your disk has
>   write cache enabled and it doesn't have flush cache bits
> 
> -EAGAIN ;)

Yep... :-(

Here's variant of the first patch with CONFIG_ALPHA and a Very Big Comment.

Ivan.

--- 2.6/drivers/ide/ide-disk.c	Sat May 29 00:43:41 2004
+++ linux/drivers/ide/ide-disk.c	Sat May 29 00:43:06 2004
@@ -1713,7 +1713,22 @@ static void ide_device_shutdown(struct d
 {
 	ide_drive_t *drive = container_of(dev, ide_drive_t, gendev);
 
+#ifdef	CONFIG_ALPHA
+	/* On Alpha, halt(8) doesn't actually turn the machine off,
+	   it puts you into the sort of firmware monitor. Typically,
+	   it's used to boot another kernel image, so it's not much
+	   different from reboot(8). Therefore, we don't need to
+	   spin down the disk in this case, especially since Alpha
+	   firmware doesn't handle disks in standby mode properly.
+	   On the other hand, it's reasonably safe to turn the power
+	   off when the shutdown process reaches the firmware prompt,
+	   as the firmware initialization takes rather long time -
+	   at least 10 seconds, which should be sufficient for
+	   the disk to expire its write cache. */
+	if (system_state != SYSTEM_POWER_OFF) {
+#else
 	if (system_state == SYSTEM_RESTART) {
+#endif
 		ide_cacheflush_p(drive);
 		return;
 	}