Re: [PATCH v3 22/77] ncr5380: Eliminate selecting state

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From	Hannes Reinecke <hare@suse.de>
Newsgroups	linux.kernel
Subject	Re: [PATCH v3 22/77] ncr5380: Eliminate selecting state
Date	Tue, 22 Dec 2015 08:20:01 +0100
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On 12/22/2015 02:18 AM, Finn Thain wrote:
> Linux v2.1.105 changed the algorithm for polling for the BSY signal
> in NCR5380_select() and NCR5380_main().
>
> Presently, this code has a bug. Back then, NCR5380_set_timer(hostdata, 1)
> meant reschedule main() after sleeping for 10 ms. Repeated 25 times this
> provided the recommended 250 ms selection time-out delay. This got broken
> when HZ became configurable.
>
> We could fix this but there's no need to reschedule the main loop. This
> BSY polling presently happens when the NCR5380_main() work queue item
> calls NCR5380_select(), which in turn schedules NCR5380_main(), which
> calls NCR5380_select() again, and so on.
>
> This algorithm is a deviation from the simpler one in atari_NCR5380.c.
> The extra complexity and state is pointless. There's no reason to
> stop selection half-way and return to to the main loop when the main
> loop can do nothing useful until selection completes.
>
> So just poll for BSY. We can sleep while polling now that we have a
> suitable workqueue.
>
> Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
>
Reviewed-by: Hannes Reinecke <hare@suse.com>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare@suse.de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
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[PATCH v3 22/77] ncr5380: Eliminate selecting state Finn Thain <fthain@telegraphics.com.au> - 2015-12-22 03:40 +0100
  Re: [PATCH v3 22/77] ncr5380: Eliminate selecting state Hannes Reinecke <hare@suse.de> - 2015-12-22 08:20 +0100

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