From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from metis.ext.pengutronix.de ([2001:67c:670:201:290:27ff:fe1d:cc33]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kcPkf-0001sO-AO for barebox@lists.infradead.org; Tue, 10 Nov 2020 09:15:46 +0000 Date: Tue, 10 Nov 2020 10:15:43 +0100 From: Sascha Hauer Message-ID: <20201110091543.GP29830@pengutronix.de> References: <20201109134430.21156-1-r.czerwinski@pengutronix.de> <20201109134430.21156-3-r.czerwinski@pengutronix.de> <907efaaf5e29ed99229c20ad2398e13b26965827.camel@lynxeye.de> <8df4ad110b83b139381e58bad3e7db82426f9371.camel@pengutronix.de> <20201110074811.GM29830@pengutronix.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20201110074811.GM29830@pengutronix.de> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "barebox" Errors-To: barebox-bounces+u.kleine-koenig=pengutronix.de@lists.infradead.org Subject: Re: [PATCH 2/8] mtd: cfi_flash: allow 0x0 mapping To: Rouven Czerwinski Cc: barebox@lists.infradead.org On Tue, Nov 10, 2020 at 08:48:11AM +0100, Sascha Hauer wrote: > On Tue, Nov 10, 2020 at 07:33:53AM +0100, Rouven Czerwinski wrote: > > On Mon, 2020-11-09 at 14:52 +0100, Lucas Stach wrote: > > > Am Montag, den 09.11.2020, 14:44 +0100 schrieb Rouven Czerwinski: > > > > Annotate the different read and write functions with > > > > zero_page_{access/faulting}. This allows the cfi_flash driver to be used > > > > on the QEMU virt machine with an enabled MMU. > > > > > > I don't like this zero-page access allow in a driver at all. If you > > > have some free address space somewhere, you could also solve this issue > > > by remapping the IO resource to somewhere else in the address space, > > > deviating from the 1:1 mapping. The Tegra PCIe host driver does this, > > > if you need some inspiration. > > > > I totally agree, remapping the IO region sounds like a much better > > choice. > > But where should it be mapped to? Just 4k upwards and hope that the area > just above the cfi flash isn't occupied by something else? Ok, here's the plan: In a board specific initcall map the memory to wherever it's convenient, modify the address of the CFI flash in the device node and add a big comment that there's nothing to see here. Sascha -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox