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 F25A0EB64DC for ; Tue, 20 Jun 2023 17:41:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229863AbjFTRlU (ORCPT ); Tue, 20 Jun 2023 13:41:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38494 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229571AbjFTRlS (ORCPT ); Tue, 20 Jun 2023 13:41:18 -0400 Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C48FDC2 for ; Tue, 20 Jun 2023 10:41:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1687282876; x=1718818876; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=YU32wILb4tnhc0im+7dQGm/pq5C2AUFMvZXmoqqj258=; b=OX0s698rgSbYgdux98NNPrzmiR1YPKjlI6gwKnvZMxo4UAKz4qgzW2ik wzhDlXowIsl/WKIxYtwwUeGC7LWLY2n0RIHtJ8T6Ev6o9D6LNpekTpNPo jcNKeHHnOoJfaEgOKi+jnrEDCjgQMOF9u5P2Scnzvvb3cD8pyiV98xU7G 0dyWvP4M/WB7Odxldzd0zUtKpNsx9A9TN2qS04qKfDXmoB9q01xT7P6dO adsLx9Zm0WUIEan6uduiHzJVv3Jk4Sj+xdX9DPdDSs/Am6WWhG+xrYktZ bIGTz0JjD8Q6imgRMlAyrdnWXklIIQX2jYzjKCMmsPlVib2msyO0ytuVW w==; X-IronPort-AV: E=McAfee;i="6600,9927,10747"; a="357427861" X-IronPort-AV: E=Sophos;i="6.00,257,1681196400"; d="scan'208";a="357427861" Received: from orsmga006.jf.intel.com ([10.7.209.51]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Jun 2023 10:41:16 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10747"; a="691531828" X-IronPort-AV: E=Sophos;i="6.00,257,1681196400"; d="scan'208";a="691531828" Received: from smile.fi.intel.com ([10.237.72.54]) by orsmga006.jf.intel.com with ESMTP; 20 Jun 2023 10:41:12 -0700 Received: from andy by smile.fi.intel.com with local (Exim 4.96) (envelope-from ) id 1qBfLq-005JYh-1p; Tue, 20 Jun 2023 20:41:10 +0300 Date: Tue, 20 Jun 2023 20:41:10 +0300 From: Andy Shevchenko To: Lucas De Marchi Cc: Jani Nikula , Andrew Morton , intel-gfx@lists.freedesktop.org, Kevin Brodsky , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, Christian =?iso-8859-1?Q?K=F6nig?= , Alex Deucher , Thomas Gleixner , Masahiro Yamada , intel-xe@lists.freedesktop.org Subject: Re: [Intel-xe] [PATCH 2/3] linux/bits.h: Add fixed-width GENMASK and BIT macros Message-ID: References: <20230509051403.2748545-1-lucas.demarchi@intel.com> <20230509051403.2748545-3-lucas.demarchi@intel.com> <87pm75kd0h.fsf@intel.com> <87mt29kc34.fsf@intel.com> <875y7igph5.fsf@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 Tue, Jun 20, 2023 at 10:25:21AM -0700, Lucas De Marchi wrote: > On Tue, Jun 20, 2023 at 05:55:19PM +0300, Andy Shevchenko wrote: > > On Tue, Jun 20, 2023 at 05:47:34PM +0300, Jani Nikula wrote: > > > On Thu, 15 Jun 2023, Andy Shevchenko wrote: > > > > On Fri, May 12, 2023 at 02:45:19PM +0300, Jani Nikula wrote: > > > >> On Fri, 12 May 2023, Andy Shevchenko wrote: > > > >> > On Fri, May 12, 2023 at 02:25:18PM +0300, Jani Nikula wrote: > > > >> >> On Fri, 12 May 2023, Andy Shevchenko wrote: > > > >> >> > On Mon, May 08, 2023 at 10:14:02PM -0700, Lucas De Marchi wrote: > > > >> >> >> Add GENMASK_U32(), GENMASK_U16() and GENMASK_U8() macros to create > > > >> >> >> masks for fixed-width types and also the corresponding BIT_U32(), > > > >> >> >> BIT_U16() and BIT_U8(). > > > >> >> > Why? > > > >> >> > > > >> >> The main reason is that GENMASK() and BIT() size varies for 32/64 bit > > > >> >> builds. > > > >> > > > > >> > When needed GENMASK_ULL() can be used (with respective castings perhaps) > > > >> > and BIT_ULL(), no? > > > >> > > > >> How does that help with making them the same 32-bit size on both 32 and > > > >> 64 bit builds? > > > > > > > > u32 x = GENMASK(); > > > > u64 y = GENMASK_ULL(); > > > > > > > > No? Then use in your code either x or y. Note that I assume that the parameters > > > > to GENMASK*() are built-time constants. Is it the case for you? > > > > > > What's wrong with wanting to define macros with specific size, depending > > > on e.g. hardware registers instead of build size? > > > > Nothing, but I think the problem is smaller than it's presented. > > not sure about big/small problem you are talking about. It's a problem > for when the *device* register is a 32b fixed width, which is > independent from the CPU you are running on. We also have registers that > are u16 and u64. Having fixed-width GENMASK and BIT helps avoiding > mistakes like below. Just to use one example, the diff below builds > fine on my 64b machine, yet it's obviously wrong: > > $ git diff diff --git a/drivers/gpu/drm/i915/gt/intel_gt_mcr.c > b/drivers/gpu/drm/i915/gt/intel_gt_mcr.c > index 0b414eae1683..692a0ad9a768 100644 > --- a/drivers/gpu/drm/i915/gt/intel_gt_mcr.c > +++ b/drivers/gpu/drm/i915/gt/intel_gt_mcr.c > @@ -261,8 +261,8 @@ static u32 rw_with_mcr_steering_fw(struct intel_gt *gt, > * No need to save old steering reg value. > */ > intel_uncore_write_fw(uncore, MTL_MCR_SELECTOR, > - REG_FIELD_PREP(MTL_MCR_GROUPID, group) | > - REG_FIELD_PREP(MTL_MCR_INSTANCEID, instance) | > + FIELD_PREP(MTL_MCR_GROUPID, group) | > + FIELD_PREP(MTL_MCR_INSTANCEID, instance) | > (rw_flag == FW_REG_READ ? GEN11_MCR_MULTICAST : 0)); > } else if (GRAPHICS_VER(uncore->i915) >= 11) { > mcr_mask = GEN11_MCR_SLICE_MASK | GEN11_MCR_SUBSLICE_MASK; > diff --git a/drivers/gpu/drm/i915/gt/intel_gt_regs.h b/drivers/gpu/drm/i915/gt/intel_gt_regs.h > index 718cb2c80f79..c42bc2900c6a 100644 > --- a/drivers/gpu/drm/i915/gt/intel_gt_regs.h > +++ b/drivers/gpu/drm/i915/gt/intel_gt_regs.h > @@ -80,8 +80,8 @@ > #define GEN11_MCR_SLICE_MASK GEN11_MCR_SLICE(0xf) > #define GEN11_MCR_SUBSLICE(subslice) (((subslice) & 0x7) << 24) > #define GEN11_MCR_SUBSLICE_MASK GEN11_MCR_SUBSLICE(0x7) > -#define MTL_MCR_GROUPID REG_GENMASK(11, 8) > -#define MTL_MCR_INSTANCEID REG_GENMASK(3, 0) > +#define MTL_MCR_GROUPID GENMASK(32, 8) > +#define MTL_MCR_INSTANCEID GENMASK(3, 0) > #define IPEIR_I965 _MMIO(0x2064) > #define IPEHR_I965 _MMIO(0x2068) > > If the driver didn't support 32b CPUs, this would even go unnoticed. So, what does prevent you from using GENMASK_ULL()? Another point, you may teach GENMASK() to issue a warning if hi and/or lo bigger than BITS_PER_LONG. I still don't see the usefulness of that churn. > Lucas De Marchi > > > And there are already header for bitfields with a lot of helpers > > for (similar) cases if not yours. > > > > > What would you use for printk format if you wanted to to print > > > GENMASK()? > > > > %lu, no? -- With Best Regards, Andy Shevchenko