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Tue, 3 Nov 2020 21:33:54 +1100 (AEDT) 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03 Nov 2020 10:27:33 +0100 From: Thomas Gleixner To: LKML Subject: [patch V3 21/37] Documentation/io-mapping: Remove outdated blurb References: 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-Mailman-Approved-At: Tue, 03 Nov 2020 21:51:18 +1100 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Juri Lelli , linux-aio@kvack.org, Peter Zijlstra , Sebastian Andrzej Siewior , Joonas Lahtinen , dri-devel@lists.freedesktop.org, virtualization@lists.linux-foundation.org, Ben Segall , Chris Mason , Huang Rui , Paul Mackerras , Gerd Hoffmann , Daniel Bristot de Oliveira , sparclinux@vger.kernel.org, Vincent Chen , Christoph Hellwig , Vincent Guittot , Paul McKenney , Max Filippov , x86@kernel.org, Russell King , linux-csky@vger.kernel.org, Ingo Molnar , David Airlie , VMware Graphics , Mel Gorman , nouveau@lists.freedesktop.org, Dave Airlie , linux-snps-arc@lists.infradead.org, Ben Skeggs , linux-xtensa@linux-xtensa.org, Arnd Bergmann , intel-gfx@lists.freedesktop.org, Roland Scheidegger , Josef Bacik , Steven Rostedt , Linus Torvalds , Alexander Viro , spice-devel@lists.freedesktop.org, David Sterba , Rodrigo Vivi , Dietmar Eggemann , linux-arm-kernel@lists.infradead.org, Jani Nikula , Chris Zankel , Michal Simek , Thomas Bogendoerfer , Nick Hu , linux-mm@kvack.org, Vineet Gupta , linux-mips@vger.kernel.org, Christian Koenig , Benjamin LaHaise , Daniel Vetter , linux-fsdevel@vger.kernel.org, Andrew Morton , linuxppc-dev@lists.ozlabs.org, "David S. Miller" , linux-btrfs@vger.kernel.org, Greentime Hu Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" 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.