From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id A3E9F30649C for ; Fri, 2 Oct 2026 15:34:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790955301; cv=none; b=ccqt/gAyT1iibga++d4Vu1JXSL1RB8sQLbxuNsBqsx97cU+4qQJC3hGw+HIDBgCh/GPwNyHne0EdC1ArvCp/6SlUssF/GpSOJJgTsHfl6hc07QLGBNZ9g/t9EtzxgAgXO/gvrf2JpEsUMVMmpA0ANr0xkBnHChHYM7iTS6bR/PM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790955301; c=relaxed/simple; bh=trtR+s01elaDJMhAurTszPiTKfZo8xAqeqlZBtV1GTo=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=tyfFyij1tBF91iCP3B+bZ7VqwJEpdK02U3ivtMuGx/hN5meFlNULtL+rwPKKvUOww0EL//+0YPTqg0KZXekCWvqK+e0bmdYCW0dLYj2ooHico+MtjYMxUSxTcr/j3oVrBsjSoQdtHCcds3+/QLWaNBgRy7f3wopZbg41CKBttYk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=VEXuqrMX; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="VEXuqrMX" 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 73E23143D; Fri, 2 Oct 2026 08:34:55 -0700 (PDT) Received: from [10.0.129.26] (e122027.cambridge.arm.com [10.0.129.26]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 4C5103F85F; Fri, 2 Oct 2026 08:34:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1790955298; bh=trtR+s01elaDJMhAurTszPiTKfZo8xAqeqlZBtV1GTo=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=VEXuqrMXiFXFNSutxilLVc1xl52bHGqQswylLZqFvnMUrcIwI06Caqk927r8F9WJK 9nladCFAkoTAOl03d6kqpdw7OlRw/TjcN8LONEkvvUKMmmtE0pGnLojeik3iE8DejM EerFmP3YjGr+4ee/d//KRDKvtI87g62aRj/TElEc= Message-ID: Date: Fri, 2 Oct 2026 16:34:52 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v12 14/15] drm/panfrost: Introduce a reset lock To: =?UTF-8?Q?Adri=C3=A1n_Larumbe?= , Boris Brezillon , Rob Herring , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Faith Ekstrand , "Marty E. Plummer" , Tomeu Vizoso , Eric Anholt , Robin Murphy , Philipp Zabel Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Collabora Kernel Team , Neil Armstrong References: <20260929-claude-fixes-v12-0-62beb08de207@collabora.com> <20260929-claude-fixes-v12-14-62beb08de207@collabora.com> From: Steven Price Content-Language: en-GB In-Reply-To: <20260929-claude-fixes-v12-14-62beb08de207@collabora.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 29/09/2026 04:44, Adrián Larumbe wrote: > So as to avoid accessing HW register while a reset is ongoing, a read/write > semaphore that envelopes the reset sequence will help driver entry points > avoid racing with it. For now, the only such racy entry point is the ioctl > that returns the current GPU timestmap. Typo: s/timestmap/timestamp > > Reviewed-by: Boris Brezillon > Signed-off-by: Adrián Larumbe Reviewed-by: Steven Price > --- > drivers/gpu/drm/panfrost/panfrost_device.c | 2 ++ > drivers/gpu/drm/panfrost/panfrost_device.h | 1 + > drivers/gpu/drm/panfrost/panfrost_drv.c | 9 ++++++--- > drivers/gpu/drm/panfrost/panfrost_job.c | 1 + > 4 files changed, 10 insertions(+), 3 deletions(-) > > diff --git a/drivers/gpu/drm/panfrost/panfrost_device.c b/drivers/gpu/drm/panfrost/panfrost_device.c > index 94d2de341838..80d8f6aed090 100644 > --- a/drivers/gpu/drm/panfrost/panfrost_device.c > +++ b/drivers/gpu/drm/panfrost/panfrost_device.c > @@ -481,6 +481,8 @@ bool panfrost_exception_needs_reset(const struct panfrost_device *pfdev, > > void panfrost_device_reset(struct panfrost_device *pfdev, bool enable_job_int) > { > + guard(rwsem_write)(&pfdev->reset.lock); > + > panfrost_gpu_soft_reset(pfdev); > > panfrost_gpu_power_on(pfdev); > diff --git a/drivers/gpu/drm/panfrost/panfrost_device.h b/drivers/gpu/drm/panfrost/panfrost_device.h > index a0b9a2145fc9..63452febb1cf 100644 > --- a/drivers/gpu/drm/panfrost/panfrost_device.h > +++ b/drivers/gpu/drm/panfrost/panfrost_device.h > @@ -165,6 +165,7 @@ struct panfrost_device { > struct { > struct workqueue_struct *wq; > struct work_struct work; > + struct rw_semaphore lock; > atomic_t pending; > } reset; > > diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c > index f77780c72a1a..571a26b84126 100644 > --- a/drivers/gpu/drm/panfrost/panfrost_drv.c > +++ b/drivers/gpu/drm/panfrost/panfrost_drv.c > @@ -41,9 +41,12 @@ static int panfrost_ioctl_query_timestamp(struct panfrost_device *pfdev, > if (ret) > return ret; > > - panfrost_cycle_counter_get(pfdev); > - *arg = panfrost_timestamp_read(pfdev); > - panfrost_cycle_counter_put(pfdev); > + /* We should not read timestamp register while the GPU is being reset */ > + scoped_guard(rwsem_read, &pfdev->reset.lock) { > + panfrost_cycle_counter_get(pfdev); > + *arg = panfrost_timestamp_read(pfdev); > + panfrost_cycle_counter_put(pfdev); > + } > > pm_runtime_put(pfdev->base.dev); > return 0; > diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c > index ab65786bf63b..4ddf4b722ddf 100644 > --- a/drivers/gpu/drm/panfrost/panfrost_job.c > +++ b/drivers/gpu/drm/panfrost/panfrost_job.c > @@ -877,6 +877,7 @@ int panfrost_jm_init(struct panfrost_device *pfdev) > INIT_WORK(&pfdev->reset.work, panfrost_reset_work); > spin_lock_init(&js->job_lock); > mutex_init(&pfdev->sched_lock); > + init_rwsem(&pfdev->reset.lock); > > js->irq = platform_get_irq_byname(to_platform_device(pfdev->base.dev), "job"); > if (js->irq < 0) >