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 18F2CC433FE for ; Wed, 13 Apr 2022 22:34:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235864AbiDMWgy (ORCPT ); Wed, 13 Apr 2022 18:36:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35150 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229772AbiDMWgy (ORCPT ); Wed, 13 Apr 2022 18:36:54 -0400 Received: from bhuna.collabora.co.uk (bhuna.collabora.co.uk [IPv6:2a00:1098:0:82:1000:25:2eeb:e3e3]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 92CBF3467E for ; Wed, 13 Apr 2022 15:34:31 -0700 (PDT) Received: from [IPV6:2a00:5f00:102:0:10b3:10ff:fe5d:4ec1] (unknown [IPv6:2a00:5f00:102:0:10b3:10ff:fe5d:4ec1]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: dmitry.osipenko) by bhuna.collabora.co.uk (Postfix) with ESMTPSA id 982E31F4762C; Wed, 13 Apr 2022 23:34:29 +0100 (BST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1649889270; bh=YG/XPhnWizXt3303tJt/IxDGAZVOLwxkOEcrQ7Z9X1I=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=WuInoSFqyOdJAlFL2xvC3Fd06QpZKkwfuYrjwHkZTkD3PIQmFEM6al0EmXS+wSFGn JZoeP7y+9bvcUjK4SH7oYB9OEMOqkZTMeDzVxNGmHqkgDa0QqmsiVLGnrJ+zRtX1C9 MUV82xVcb7MhPRF/M/j7O56roc/EOLNaJoQERHg6lx1P5tE8M0+rZDp7etRC029xfg MyoxvhheqezqCf0zOF5inflSCSTNOoB7aeRKetuaBlY7nhTNK9cIHW9vowIHJy0odE Bd4L9c6oS5vzxekRzWMhDNn/jwlaq7YcrmLPUn7Nmrj6LLiYUOvXQzQnQBs9KBmAG9 2EMXQRqKGBMYA== Message-ID: <9bb76a5b-d5d7-6f43-ed8a-e6782dda8568@collabora.com> Date: Thu, 14 Apr 2022 01:34:26 +0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.7.0 Subject: Re: [PATCH v2] drm/tegra: Stop using iommu_present() Content-Language: en-US To: Robin Murphy , thierry.reding@gmail.com Cc: jonathanh@nvidia.com, dri-devel@lists.freedesktop.org, linux-tegra@vger.kernel.org, iommu@lists.linux-foundation.org References: <1f7c304a79b8b8dd5d4716786cae7502a0cc31f5.1649684782.git.robin.murphy@arm.com> From: Dmitry Osipenko In-Reply-To: <1f7c304a79b8b8dd5d4716786cae7502a0cc31f5.1649684782.git.robin.murphy@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-tegra@vger.kernel.org On 4/11/22 16:46, Robin Murphy wrote: > Refactor the confusing logic to make it both clearer and more robust. If > the host1x parent device does have an IOMMU domain then iommu_present() > is redundantly true, while otherwise for the 32-bit DMA mask case it > still doesn't say whether the IOMMU driver actually knows about the DRM > device or not. > > Signed-off-by: Robin Murphy > --- > > v2: Fix logic for older SoCs and clarify. > > drivers/gpu/drm/tegra/drm.c | 28 ++++++++++++++++++++-------- > 1 file changed, 20 insertions(+), 8 deletions(-) > > diff --git a/drivers/gpu/drm/tegra/drm.c b/drivers/gpu/drm/tegra/drm.c > index 9464f522e257..4f2bdab31064 100644 > --- a/drivers/gpu/drm/tegra/drm.c > +++ b/drivers/gpu/drm/tegra/drm.c > @@ -1092,6 +1092,19 @@ static bool host1x_drm_wants_iommu(struct host1x_device *dev) > struct host1x *host1x = dev_get_drvdata(dev->dev.parent); > struct iommu_domain *domain; > > + /* For starters, this is moot if no IOMMU is available */ > + if (!device_iommu_mapped(&dev->dev)) > + return false; > + > + /* > + * Tegra20 and Tegra30 don't support addressing memory beyond the > + * 32-bit boundary, so the regular GATHER opcodes will always be > + * sufficient and whether or not the host1x is attached to an IOMMU > + * doesn't matter. > + */ > + if (host1x_get_dma_mask(host1x) <= DMA_BIT_MASK(32)) > + return true; > + > /* > * If the Tegra DRM clients are backed by an IOMMU, push buffers are > * likely to be allocated beyond the 32-bit boundary if sufficient > @@ -1122,14 +1135,13 @@ static bool host1x_drm_wants_iommu(struct host1x_device *dev) > domain = iommu_get_domain_for_dev(dev->dev.parent); > > /* > - * Tegra20 and Tegra30 don't support addressing memory beyond the > - * 32-bit boundary, so the regular GATHER opcodes will always be > - * sufficient and whether or not the host1x is attached to an IOMMU > - * doesn't matter. > + * At the moment, the exact type of domain doesn't actually matter. > + * Only for 64-bit kernels might this be a managed DMA API domain, and > + * then only on newer SoCs using arm-smmu, since tegra-smmu doesn't > + * support default domains at all, and since those SoCs are the same > + * ones with extended GATHER support, even if it's a passthrough domain > + * it can still work out OK. > */ > - if (!domain && host1x_get_dma_mask(host1x) <= DMA_BIT_MASK(32)) > - return true; > - > return domain != NULL; > } > > @@ -1149,7 +1161,7 @@ static int host1x_drm_probe(struct host1x_device *dev) > goto put; > } > > - if (host1x_drm_wants_iommu(dev) && iommu_present(&platform_bus_type)) { > + if (host1x_drm_wants_iommu(dev)) { > tegra->domain = iommu_domain_alloc(&platform_bus_type); > if (!tegra->domain) { > err = -ENOMEM; Robin, thank you for the updated version. The patch looks okay to me. Reviewed-by: Dmitry Osipenko A bit later I'll also will give it a test, just to be sure because we had problems with that function in the past.