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bh=q62aMHmAxbn1lufZfZAjq5qpqwqeRKoV0pt8VHtML4U=; b=VodykyzYLP8iNG4jjO6iCA5x48oeK+d//LgOhvHxgg4A9NadNsC2pxoHcsSPHjaiYSk0bhEn/sSVKHg9UzjTDq7vtBCGGfRwy0wdIsMD0R9oyLAR7uqMr2cM7I6p3aTIlDx9LjGy0MCJFdptYB38QM3uC9W6Yam4m7v1Xpnih9g= 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=1768831430; 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=q62aMHmAxbn1lufZfZAjq5qpqwqeRKoV0pt8VHtML4U=; b=gh5Q6yQsaf2If7qeHRFmZm12lFFILlQp0LA9EDdG/bj2FvfqEKmIr1T2dBRqxkUc fXH18IRmY4pSWVLU/FrKZzEH1n6ZxyZ/I9IxCwJ3Y0BkZBKGkxOzKrJm6Y3/BAYabHJ O0QfYmGv8Le3T1BuLfigtAEQeLYJP3ByA7YMmyfQ= Received: by mx.zohomail.com with SMTPS id 1768831429842878.6665974799806; Mon, 19 Jan 2026 06:03:49 -0800 (PST) Message-ID: Date: Mon, 19 Jan 2026 15:03:44 +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 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 19/01/2026 à 13:32, Will Deacon a écrit : > On Wed, Jan 14, 2026 at 02:10:48PM +0100, Benjamin Gaignard wrote: >> 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(). > But that just writes an invalid descriptor and doesn't appear to invalidate > the TLB at all. > >> That clear BIT(0) so the hardware knows the page is invalid. >> Do I have miss something here ? > Yes, the TLB structure needs to be invalidated so that the page-table > walker sees the new value that you have written in memory. > > The rockchip driver gets this correct... Rockchip hardware have a ZAP_ONE_LINE register which didn't exist on Verisilicon hardware. I have tried to use VSI_MMU_BIT_FLUSH on VSI driver after unmapping iova but it doesn't work. So far calling dma_sync_single_for_device() seems to be enough to make iommu and video decoder work together. Regards, Benjamin > Will >