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Tue, 3 Nov 2020 10:33:52 +0000 (UTC) Message-Id: <20201103095858.734064977@linutronix.de> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1604399629; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: references:references; bh=GQtIeN+bNrXtdDJbIY1/lT5u2Qlmlecyg45ylimAqeo=; b=otNm1FLhC7ruMh7oNXQtNETNU6+54RFk+t2LyeEF9d9+kDoZ9Kh8ZPgA+UB8A6JQ1ZXrGj 0TPeQl8iy37SQzf3hhxJ0YH8tjvvuOPaAqFoJKHafSPmEiutw0Ud/5TB6XtJVn4M9v5QlN Kc0YPCEkVxgY8QSHdaCi6xZgLgOgc1LgMVaGrZjI4AUGq0ZlUKuDX4Xk4y+i0m9xE3dk86 7GNBZMVBc/q+vRf7Zxdqgcl3bL7dPvuY81X2pyGhr1m48UNO2c+I7V2+wunozMP8FhvNCm gkFktETWxncmi0cgpUqLzaSL8knV0VimchG0Urhi5o5DvILy9hDHjs2CmUtXqQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1604399629; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: references:references; bh=GQtIeN+bNrXtdDJbIY1/lT5u2Qlmlecyg45ylimAqeo=; b=aDUoEgUsKRf0mAVHG33KZuw3tdfR+OUYkG1a4FnTBJVD3Vb06TvF7LUgRRezOsbA4xMida qFHqtJWvRi1kHPBw== Date: Tue, 03 Nov 2020 10:27:33 +0100 From: Thomas Gleixner To: LKML Cc: Linus Torvalds , Peter Zijlstra , Paul McKenney , Christoph Hellwig , Sebastian Andrzej Siewior , Andrew Morton , linux-mm@kvack.org, Alexander Viro , Benjamin LaHaise , linux-fsdevel@vger.kernel.org, linux-aio@kvack.org, Chris Mason , Josef Bacik , David Sterba , linux-btrfs@vger.kernel.org, x86@kernel.org, Vineet Gupta , linux-snps-arc@lists.infradead.org, Russell King , Arnd Bergmann , linux-arm-kernel@lists.infradead.org, linux-csky@vger.kernel.org, Michal Simek , Thomas Bogendoerfer , linux-mips@vger.kernel.org, Nick Hu , Greentime Hu , Vincent Chen , Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , linuxppc-dev@lists.ozlabs.org, "David S. Miller" , sparclinux@vger.kernel.org, Chris Zankel , Max Filippov , linux-xtensa@linux-xtensa.org, Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Christian Koenig , Huang Rui , David Airlie , Daniel Vetter , dri-devel@lists.freedesktop.org, VMware Graphics , Roland Scheidegger , Dave Airlie , Gerd Hoffmann , virtualization@lists.linux-foundation.org, spice-devel@lists.freedesktop.org, Ben Skeggs , nouveau@lists.freedesktop.org, Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , intel-gfx@lists.freedesktop.org Subject: [patch V3 21/37] Documentation/io-mapping: Remove outdated blurb References: <20201103092712.714480842@linutronix.de> MIME-Version: 1.0 Content-transfer-encoding: 8-bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: The implementation details in the documentation are outdated and not really helpful. Remove them. Signed-off-by: Thomas Gleixner --- V3: New patch --- Documentation/driver-api/io-mapping.rst | 22 ---------------------- 1 file changed, 22 deletions(-) --- a/Documentation/driver-api/io-mapping.rst +++ b/Documentation/driver-api/io-mapping.rst @@ -73,25 +73,3 @@ for pages mapped with io_mapping_map_wc. At driver close time, the io_mapping object must be freed:: void io_mapping_free(struct io_mapping *mapping) - -Current Implementation -====================== - -The initial implementation of these functions uses existing mapping -mechanisms and so provides only an abstraction layer and no new -functionality. - -On 64-bit processors, io_mapping_create_wc calls ioremap_wc for the whole -range, creating a permanent kernel-visible mapping to the resource. The -map_atomic and map functions add the requested offset to the base of the -virtual address returned by ioremap_wc. - -On 32-bit processors with HIGHMEM defined, io_mapping_map_atomic_wc uses -kmap_atomic_pfn to map the specified page in an atomic fashion; -kmap_atomic_pfn isn't really supposed to be used with device pages, but it -provides an efficient mapping for this usage. - -On 32-bit processors without HIGHMEM defined, io_mapping_map_atomic_wc and -io_mapping_map_wc both use ioremap_wc, a terribly inefficient function which -performs an IPI to inform all processors about the new mapping. This results -in a significant performance penalty.