From mboxrd@z Thu Jan  1 00:00:00 1970
From: thomas.petazzoni@free-electrons.com (Thomas Petazzoni)
Date: Fri, 21 Feb 2014 16:11:08 +0100
Subject: pci-mvebu driver on km_kirkwood
In-Reply-To: <2193926.ls2teBqnfK@wuerfel>
References: <53039894.10905@keymile.com> <53074584.5010202@keymile.com>
 <20140221144708.48559045@skate> <2193926.ls2teBqnfK@wuerfel>
Message-ID: <20140221161108.50a4c932@skate>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

Dear Arnd Bergmann,

On Fri, 21 Feb 2014 16:05:16 +0100, Arnd Bergmann wrote:

> >  *) I don't know if the algorithm to split the BAR into multiple
> >     windows is going to be trivial.
> 
> The easiest solution would be to special case 'size is between
> 128MB+1 and 192MB' if that turns out to be the most interesting
> case. It's easy enough to make the second window smaller than 64MB
> if we want.
> 
> If we want things to be a little fancier, we could use:
> 
> 	switch (size) {
> 		case (SZ_32M+1) ... (SZ_32M+SZ_16M):
> 			size2 = size - SZ_32M;
> 			size -= SZ_32M;
> 			break;
> 		case (SZ_64M+1) ... (SZ_64M+SZ_32M):
> 			size2 = size - SZ_64M;
> 			size -= SZ_64M;
> 			break;
> 		case (SZ_128M+1) ... (SZ_128M+SZ_64M):
> 			size2 = size - SZ_128M;
> 			size -= SZ_128M;
> 			break;
> 	};

What if the size of your BAR is 128 MB + 64 MB + 32 MB ? Then you need
three windows, and your algorithm doesn't work :-)

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com