From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 021BEC433F5 for ; Wed, 23 Feb 2022 11:38:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240024AbiBWLim (ORCPT ); Wed, 23 Feb 2022 06:38:42 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34580 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240010AbiBWLij (ORCPT ); Wed, 23 Feb 2022 06:38:39 -0500 Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1808B92D37; Wed, 23 Feb 2022 03:38:11 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1645616292; x=1677152292; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=12JycTJlECTUq0lO/omhbnhyj0Dc1BQX7rKXfLcSDC8=; b=lB7KDa65fHyDIGcJZdhxH/yWHeitjIc4ittyAqOZ8HyxobOVKfBFpJ2f NY0FQ1UYNIPXV3QlL9NvViwSyBvAnNGG1OANILwx2Zwre1NGgmzyuO0Tk oRyy5qSC7lOvoJT4PzzqPu7EWUm3t7agNI4wLS2i4QtTqUxgfQkk/D+xh Dt7rSTZfekr7FO/n6cv8dBE4SmIyrXkj10R9TnZ59wUneiUqkqdA1INGe sksEhVTLhwBwbd1HJNRafGDZ7AWmNBTRW78oImp7x7Tfzyx7jqCJujFSJ 7x+VjYT4DC4Pr+5JXwGWOrZSTuXyFsNQYlddIV+pVyeTEeJMQ2zQgM9Go w==; X-IronPort-AV: E=McAfee;i="6200,9189,10266"; a="232565385" X-IronPort-AV: E=Sophos;i="5.88,390,1635231600"; d="scan'208";a="232565385" Received: from orsmga006.jf.intel.com ([10.7.209.51]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Feb 2022 03:38:11 -0800 X-IronPort-AV: E=Sophos;i="5.88,390,1635231600"; d="scan'208";a="508403291" Received: from smile.fi.intel.com ([10.237.72.59]) by orsmga006-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Feb 2022 03:38:09 -0800 Received: from andy by smile.fi.intel.com with local (Exim 4.95) (envelope-from ) id 1nMpxO-007OWU-Tn; Wed, 23 Feb 2022 13:37:18 +0200 Date: Wed, 23 Feb 2022 13:37:18 +0200 From: Andy Shevchenko To: Greg Kroah-Hartman , Bjorn Helgaas Cc: Christoph Hellwig , Jiri Slaby , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 2/2] serial: 8250_lpss: Switch to pcim_iomap() instead of pci_ioremap_bar() Message-ID: References: <20220215134359.78169-1-andriy.shevchenko@linux.intel.com> <20220215134359.78169-2-andriy.shevchenko@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 23, 2022 at 12:13:07PM +0100, Greg Kroah-Hartman wrote: > On Wed, Feb 23, 2022 at 01:08:07PM +0200, Andy Shevchenko wrote: > > On Tue, Feb 22, 2022 at 08:02:10AM -0800, Christoph Hellwig wrote: > > > On Tue, Feb 22, 2022 at 10:14:16AM +0100, Jiri Slaby wrote: > > > > On 16. 02. 22, 9:53, Christoph Hellwig wrote: > > > > > On Tue, Feb 15, 2022 at 03:43:59PM +0200, Andy Shevchenko wrote: > > > > > > The pci_iounmap() doesn't cover all the cases where resource should > > > > > > be unmapped. Instead of spreading it more, replace the pci_ioremap_bar() > > > > > > with pcim_iomap() which uses managed resource approach. > > > > > > > > > > pcim_iomap requires the use of ioreadX/iowriteX and thus runtime > > > > > overhead. So in doubt please add a pcim_ioremap_bar instead of forcing > > > > > the legacy iomap/ioread/iowrite API onto modern drivers tht can't > > > > > support legacy port I/O. > > > > > > > > Hmm, the driver combines pci_ioremap_bar with pci_iounmap. pci_iounmap does > > > > the right thing after all, but is that correct? And this driver is not > > > > alone, this shows more: > > > > git grep -E 'pci_iounmap|pci_ioremap_bar' `git grep -l pci_iounmap \`git > > > > grep -l pci_ioremap_bar\`` > > > > > > I think it is wrong. It is not actively harmful unlike the the > > > combination of pci_iomap and then later use of accessors from the > > > ioremap family, but still not exactly a good idea. > > > > > > In a perfect world we'd have some different annotation from __iomem > > > for the whole iomap family of functions. > > > > So, what would be your suggestion for a) backportable change b) cleanup for > > the current and future drivers? > > Worry about getting it right first. Only after that should you even > consider stable tree backports. There's usually no reason you can't > just take the same change there as well. And if not, we will work > through it :) Okay, so if I read this thread correctly Christoph suggests to introduce pcim_ioremap_bar() and then use it. Am I right? Christoph, since we are on the topic about pcim_*() APIs, can you chime in the discussion [1] about IRQ vectors allocation? [1]: https://lore.kernel.org/all/20210607153916.1021016-1-zhengdejin5@gmail.com/ -- With Best Regards, Andy Shevchenko