From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 14049B6F15 for ; Mon, 30 Nov 2009 17:14:57 +1100 (EST) Subject: Re: [RFC PATCH v2 08/11] powerpc: gamecube/wii: early debugging using usbgecko From: Benjamin Herrenschmidt To: Albert Herranz In-Reply-To: <4B135D3D.9030006@yahoo.es> References: <1259441037-15725-1-git-send-email-albert_herranz@yahoo.es> <1259441037-15725-9-git-send-email-albert_herranz@yahoo.es> <1259536695.2076.40.camel@pasglop> <4B135D3D.9030006@yahoo.es> Content-Type: text/plain; charset="UTF-8" Date: Mon, 30 Nov 2009 17:14:52 +1100 Message-ID: <1259561692.2076.78.camel@pasglop> Mime-Version: 1.0 Cc: linuxppc-dev@lists.ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Mon, 2009-11-30 at 06:50 +0100, Albert Herranz wrote: > Benjamin Herrenschmidt wrote: > > On Sat, 2009-11-28 at 21:43 +0100, Albert Herranz wrote: > >> + * Prepare again the same BAT for MMU_init. > >> + * This allows udbg I/O to continue working after the MMU is > >> + * turned on for real. > >> + * > >> + * We are assuming here that exi_io_base is identity mapped. > >> + */ > >> + addr = ((unsigned long)exi_io_base) & 0xffff0000; > >> + setbat(1, addr, addr, 128*1024, PAGE_KERNEL_NCG); > > > > How do you prevent that from overlapping otherwise valid kernel > > mappings ? > > > > ug_udbg_init() is called from ppc_md.init_early. > It doesn't overlap any valid kernel mappings because exi_io_base is > hardcoded to an i/o region not used yet by the kernel. But that doesn't allocate virtual space does it ? > See udbg_early_grab_exi_io_base(). Yeah, I see that: +#if defined(CONFIG_GAMECUBE) + return (void __iomem *)0x0c006800; +#elif defined(CONFIG_WII) + return (void __iomem *)0x0d006800; +#else So you'll have BATs floating over user addresses ? That sounds fishy :-) It should be trivial to just create a fixmap entry instead. That will give you a virtual address that is known at compile time (so you can use it from head_32.S as well for setting up your BAT). Actually you probably need more than one entry in there since it needs to be big enough to cover a BAT min size and be aligned, but it's not -that- hard to do (I think x86 does similar tricks in their fixmap iirc) > The setbat just prepares again, exactly in the same way, the same BAT that we got > setup by setup_usbgecko_bat in head_32.S. .../... > > You need to allocate the virtual space. For a debug thing like that, you > > could use the fixmap. In fact, I think we should create a fixmap entry > > or two always available for use by early debug. > > > > Or give us back ppc_md.setup_io_mappings :) Not happening :-) Or if you get one, it will allocate virtual addresses and so you cannot rely on an identity mapping.