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 X-Spam-Level: X-Spam-Status: No, score=-16.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 70A18C433FE for ; Fri, 17 Sep 2021 10:51:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4FABE6120D for ; Fri, 17 Sep 2021 10:51:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241859AbhIQKw1 (ORCPT ); Fri, 17 Sep 2021 06:52:27 -0400 Received: from foss.arm.com ([217.140.110.172]:51346 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232848AbhIQKwY (ORCPT ); Fri, 17 Sep 2021 06:52:24 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 8DB3C101E; Fri, 17 Sep 2021 03:51:02 -0700 (PDT) Received: from [192.168.1.179] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 695633F5A1; Fri, 17 Sep 2021 03:51:01 -0700 (PDT) Subject: Re: [PATCH v2] drm/panfrost: Calculate lock region size correctly To: Rob Herring , Tomeu Vizoso , Alyssa Rosenzweig , Boris Brezillon Cc: Daniel Vetter , David Airlie , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org References: <20210903094957.74560-1-steven.price@arm.com> From: Steven Price Message-ID: <4592bd5e-5110-1568-9373-232c66f9fefe@arm.com> Date: Fri, 17 Sep 2021 11:51:00 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <20210903094957.74560-1-steven.price@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/09/2021 10:49, Steven Price wrote: > It turns out that when locking a region, the region must be a naturally > aligned power of 2. The upshot of this is that if the desired region > crosses a 'large boundary' the region size must be increased > significantly to ensure that the locked region completely covers the > desired region. Previous calculations (including in kbase for the > proprietary driver) failed to take this into account. > > Since it's known that the lock region must be naturally aligned we can > compute the required size by looking at the highest bit position which > changes between the start/end of the lock region (subtracting 1 from the > end because the end address is exclusive). The start address is then > aligned based on the size (this is technically unnecessary as the > hardware will ignore these bits, but the spec advises to do this "to > avoid confusion"). > > Reviewed-by: Boris Brezillon > Signed-off-by: Steven Price Pushed to drm-misc-next, thanks for the reviews. Steve > --- > drivers/gpu/drm/panfrost/panfrost_mmu.c | 30 +++++++++++++++++++------ > 1 file changed, 23 insertions(+), 7 deletions(-) > > diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c b/drivers/gpu/drm/panfrost/panfrost_mmu.c > index dfe5f1d29763..e2629b8d6a02 100644 > --- a/drivers/gpu/drm/panfrost/panfrost_mmu.c > +++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c > @@ -58,17 +58,33 @@ static int write_cmd(struct panfrost_device *pfdev, u32 as_nr, u32 cmd) > } > > static void lock_region(struct panfrost_device *pfdev, u32 as_nr, > - u64 iova, u64 size) > + u64 region_start, u64 size) > { > u8 region_width; > - u64 region = iova & PAGE_MASK; > + u64 region; > + u64 region_end = region_start + size; > > - /* The size is encoded as ceil(log2) minus(1), which may be calculated > - * with fls. The size must be clamped to hardware bounds. > + if (!size) > + return; > + > + /* > + * The locked region is a naturally aligned power of 2 block encoded as > + * log2 minus(1). > + * Calculate the desired start/end and look for the highest bit which > + * differs. The smallest naturally aligned block must include this bit > + * change, the desired region starts with this bit (and subsequent bits) > + * zeroed and ends with the bit (and subsequent bits) set to one. > */ > - size = max_t(u64, size, AS_LOCK_REGION_MIN_SIZE); > - region_width = fls64(size - 1) - 1; > - region |= region_width; > + region_width = max(fls64(region_start ^ (region_end - 1)), > + const_ilog2(AS_LOCK_REGION_MIN_SIZE)) - 1; > + > + /* > + * Mask off the low bits of region_start (which would be ignored by > + * the hardware anyway) > + */ > + region_start &= GENMASK_ULL(63, region_width); > + > + region = region_width | region_start; > > /* Lock the region that needs to be updated */ > mmu_write(pfdev, AS_LOCKADDR_LO(as_nr), region & 0xFFFFFFFFUL); >