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bh=4hNT9bMCTFBIbSQvqXd0vDReNnQZh/9obugkKAGLY2o=; b=Z3ypKbyrmN4UqyBQ/OpBF0Xt+PTnoN3lrsmi+bnS58U5VogPFE79P61hocJTfKf5V4yeQUd9Dfy44nOaW/WC25OHnrTWbgoBS3LtfodwTnaOr6emvOzBy7xsnqNFLv3pUEjJzX10wSd/uftfocWF4QyMhk9grdCDQXvxtzl1+lU= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass header.i=collabora.com; spf=pass smtp.mailfrom=benjamin.gaignard@collabora.com; dmarc=pass header.from= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1768396254; s=zohomail; d=collabora.com; i=benjamin.gaignard@collabora.com; h=Message-ID:Date:Date:MIME-Version:Subject:Subject:To:To:Cc:Cc:References:From:From:In-Reply-To:Content-Type:Content-Transfer-Encoding:Message-Id:Reply-To; bh=4hNT9bMCTFBIbSQvqXd0vDReNnQZh/9obugkKAGLY2o=; b=X0ks54VN6tfrUJdG2MPakQ5UFB3h6zKvKNfKKUpWpfUgWbgTHNnEgeD2+PI0HybV /b/+j9T6abRwqDw2PyUsCs8QMYnRBo+QkfQoyl0BFB0gA9BjsbvJnHM3TbfTefcK6+5 tNFmo4rlMi7g8x4CgqPkwptI/h8vsuTzlNYwEVbs= Received: by mx.zohomail.com with SMTPS id 1768396253114813.88687353656; Wed, 14 Jan 2026 05:10:53 -0800 (PST) Message-ID: Date: Wed, 14 Jan 2026 14:10:48 +0100 Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v11 3/7] iommu: Add verisilicon IOMMU driver To: Will Deacon Cc: joro@8bytes.org, robin.murphy@arm.com, robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org, heiko@sntech.de, nicolas.dufresne@collabora.com, p.zabel@pengutronix.de, mchehab@kernel.org, iommu@lists.linux.dev, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-rockchip@lists.infradead.org, linux-media@vger.kernel.org, kernel@collabora.com References: <20260107101005.84039-1-benjamin.gaignard@collabora.com> <20260107101005.84039-4-benjamin.gaignard@collabora.com> <68a49f8b-178c-4fa2-b4a9-315ad602271d@collabora.com> Content-Language: en-US From: Benjamin Gaignard In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Le 14/01/2026 à 13:59, Will Deacon a écrit : > On Tue, Jan 13, 2026 at 05:25:38PM +0100, Benjamin Gaignard wrote: >> Le 13/01/2026 à 17:10, Will Deacon a écrit : >>> Hi Benjamin, >>> >>> Thanks for posting a v11. >>> >>> On Wed, Jan 07, 2026 at 11:09:53AM +0100, Benjamin Gaignard wrote: >>>> The Verisilicon IOMMU hardware block can be found in combination >>>> with Verisilicon hardware video codecs (encoders or decoders) on >>>> different SoCs. >>>> Enable it will allow us to use non contiguous memory allocators >>>> for Verisilicon video codecs. >>>> If both decoder and this iommu driver are compiled has modules >>>> there is undefined symboles issues so this iommu driver could >>>> only be compiled has built-in. >>>> >>>> Signed-off-by: Benjamin Gaignard >>>> --- >>>> changes in version 11: >>>> - Fix dependency issue when decoder driver is build as module. >>>> >>>> drivers/iommu/Kconfig | 11 + >>>> drivers/iommu/Makefile | 1 + >>>> drivers/iommu/vsi-iommu.c | 808 ++++++++++++++++++++++++++++++++++++++ >>>> include/linux/vsi-iommu.h | 21 + >>>> 4 files changed, 841 insertions(+) >>>> create mode 100644 drivers/iommu/vsi-iommu.c >>>> create mode 100644 include/linux/vsi-iommu.h >>> Based on your reply to v9: >>> >>> https://lore.kernel.org/all/0eff8b1a-c45f-47b1-a871-59f4a0101f0f@collabora.com/ >>> >>> I took another look at this to see whether it had changed significantly >>> from v6 when compared to the rockchip driver. Sadly, they still look >>> very similar to me and I continue to suspect that the hardware is a >>> derivative. I really don't understand why having a shared implementation >>> of the default domain ops is difficult or controversial. Have you tried >>> to write it? >>> >>> However, given that nobody from the Rockchip side has contributed to the >>> discussion and you claim that this is a distinct piece of IP, I don't >>> want to block the merging of the driver by leaving the conversation >>> hanging. >>> >>> There is still one thing I don't understand (which, amusingly, the >>> rockchip driver doesn't seem to suffer from): >>> >>>> +static void vsi_iommu_flush_tlb_all(struct iommu_domain *domain) >>>> +{ >>>> + struct vsi_iommu_domain *vsi_domain = to_vsi_domain(domain); >>>> + struct list_head *pos; >>>> + unsigned long flags; >>>> + >>>> + spin_lock_irqsave(&vsi_domain->lock, flags); >>>> + >>>> + list_for_each(pos, &vsi_domain->iommus) { >>>> + struct vsi_iommu *iommu; >>>> + int ret; >>>> + >>>> + iommu = list_entry(pos, struct vsi_iommu, node); >>>> + ret = pm_runtime_resume_and_get(iommu->dev); >>>> + if (ret < 0) >>>> + continue; >>>> + >>>> + spin_lock(&iommu->lock); >>>> + >>>> + writel(VSI_MMU_BIT_FLUSH, iommu->regs + VSI_MMU_FLUSH_BASE); >>>> + writel(0, iommu->regs + VSI_MMU_FLUSH_BASE); >>>> + >>>> + spin_unlock(&iommu->lock); >>>> + pm_runtime_put_autosuspend(iommu->dev); >>>> + } >>>> + >>>> + spin_unlock_irqrestore(&vsi_domain->lock, flags); >>>> +} >>> [...] >>> >>>> +static const struct iommu_ops vsi_iommu_ops = { >>>> + .identity_domain = &vsi_identity_domain, >>>> + .release_domain = &vsi_identity_domain, >>>> + .domain_alloc_paging = vsi_iommu_domain_alloc_paging, >>>> + .of_xlate = vsi_iommu_of_xlate, >>>> + .probe_device = vsi_iommu_probe_device, >>>> + .release_device = vsi_iommu_release_device, >>>> + .device_group = generic_single_device_group, >>>> + .owner = THIS_MODULE, >>>> + .default_domain_ops = &(const struct iommu_domain_ops) { >>>> + .attach_dev = vsi_iommu_attach_device, >>>> + .map_pages = vsi_iommu_map, >>>> + .unmap_pages = vsi_iommu_unmap, >>>> + .flush_iotlb_all = vsi_iommu_flush_tlb_all, >>> This has no callers and so your unmap routine appears to be broken. >> It is a leftover of previous attempt to allow video decoder to clean/flush >> the iommu by using a function from the API. >> Now it is using vsi_iommu_restore_ctx(). >> I while remove it in version 12. > Don't you still need some invalidation on the unmap path? In vsi_iommu_unmap_iova() page is invalided by calling vsi_mk_pte_invalid(). That clear BIT(0) so the hardware knows the page is invalid. Do I have miss something here ? Benjamin > > Will >