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To: linux-arm-kernel@lists.infradead.org, linux@armlinux.org.uk, Linux kernel mailing list Message-ID: Date: Tue, 6 Aug 2019 18:49:52 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190806_061959_953791_FB981371 X-CRM114-Status: GOOD ( 11.19 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: thomas.petazzoni@free-electrons.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi, I am trying to port a machine based on arm926 with MMU, having 64MB of RAM. I am trying to understand the difference between: machine specific static I/O mappings which are done via iotable_init() (done via callback .map_io in DT_MACHINE_START) and dynamic I/O mappings done via ioremap() In the kernel docs/mailing list, I have encountered a statement which states: "with machine specific static I/O mappings which are done via iotable_init(), registers can be mapped at the upper end of vmalloc area so that one can use as little of the VA space as possible so vmalloc and friends have a better chance of getting memory" I am writing board initialization C file and got stuck at .map_io callback function, whether to define it or not. If yes, under what scenario should I do it now-a-days I think less boards are using iotable_init(). (is this defunct) ? I might be wrong here Can't I use ioremap and do dynamic mappings when ever required via device tree ? If I do so will I encounter any problems with vmalloc area. Thanks & Regards -- Suniel Mahesh _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel