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 1kd9Uw-0000uh-0b for barebox@lists.infradead.org; Thu, 12 Nov 2020 10:06:34 +0000 Date: Thu, 12 Nov 2020 11:06:31 +0100 From: Sascha Hauer Message-ID: <20201112100631.GG29830@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> <20201110091543.GP29830@pengutronix.de> <25af706b-3cb1-c7d0-579a-b900ef674692@pengutronix.de> <0e23114b-624f-c789-531f-1d65fd8cbf92@pengutronix.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <0e23114b-624f-c789-531f-1d65fd8cbf92@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: Ahmad Fatoum Cc: barebox@lists.infradead.org, Rouven Czerwinski On Tue, Nov 10, 2020 at 10:43:30AM +0100, Ahmad Fatoum wrote: > On 11/10/20 10:36 AM, Ahmad Fatoum wrote: > > Hi, > > > > On 11/10/20 10:15 AM, Sascha Hauer wrote: > >> 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. > > > > The device tree specification defines a "virtual-reg property [that] specifies > > an effective address that maps to the first physical address specified in > > the reg property of the device node. This property enables boot programs to > > provide client programs with virtual-to-physical mappings that have been set up". > > > > So, how about a tad more generic approach: > > > > - barebox device tree extends cfi-flash node with virtual-reg of appropriate > > location > > - Define a of_iomap() function that > > Or rather a more generic name, like dev_ioremap?.(In that case > !CONFIG_OF is the same as MMU off). I wouldn't use ioremap as name when the function has a different semantics, but other than that: Sounds good. Make it so! 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