linux-kernel - Re: [PATCH] gpu:drm:Change calls to mdelay to msleep in the functions,send_pkg_prepare and send_pkg_done for the file,mdfld_dsi_pkg

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Message-ID: <20150112161233.GC16118@ulmo.nvidia.com>
Date:	Mon, 12 Jan 2015 17:12:34 +0100
From:	Thierry Reding <treding@...dia.com>
To:	Alan Cox <alan@...ux.intel.com>
CC:	Nicholas Krause <xerofoify@...il.com>, <airlied@...ux.ie>,
	<airlied@...hat.com>, <damien.lespiau@...el.com>,
	<dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] gpu:drm:Change calls to mdelay to msleep in the
 functions,send_pkg_prepare and send_pkg_done for the
 file,mdfld_dsi_pkg_sender.c

On Mon, Jan 12, 2015 at 01:29:27PM +0000, Alan Cox wrote:
> On Sat, 2015-01-10 at 23:31 -0500, Nicholas Krause wrote:
> > Changes various calls in the functions,send_pkg_prepare and send_pkg_done
> > for mdelay to msleep. These changes are needed due to use working with
> > various sleep modes supported by this hardware and thus needing to sleep
> > for a small duration instead of using the respectful delay function due
> > to the need to sleep rather then busy loop the CPU(s) and waste CPU cycles
> > on the system that could be used to handle other tasks.
> > 
> > Signed-off-by: Nicholas Krause <xerofoify@...il.com>
> 
> NAK
> 
> Like every other TODO you've been mucking with at random this one is
> there for a reason.
> 
> We can't sleep at this point.

From a quick look it seems like the only reason why we can't sleep is
because sender->lock is a spinlock. But it would seem that it could
simply be a mutex, in which case the delays could become sleeps.

Do you happen to remember if there were specific reasons to make this a
spinlock rather than a mutex?

Thierry

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