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Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vhoRG-000000020dG-3Ynk; Mon, 19 Jan 2026 12:33:00 +0000 Received: from tor.source.kernel.org ([2600:3c04:e001:324:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vhoRD-000000020cs-35ER; Mon, 19 Jan 2026 12:32:56 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id BA3256014E; Mon, 19 Jan 2026 12:32:54 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 34E65C116C6; Mon, 19 Jan 2026 12:32:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1768825974; bh=M+d6u8jNMJOG/dvieHbaSobR94YjAiJkXgQzt7gGqGY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=AedT0N6xsVrBAyEJQwxwMI7L0E1ha0dhwopq7LOvX6bGNGP/Hl2efB2FDeJWXCqHs 3M5e5CQKpAAZC4tSjvi4Vjy7OCPhNHVtZs36enVffdaRm16stc0+WGqN5AAwK8l/kD jyyFF0tDkMTD/uMk9bRke/+5h9dxF/iUdvJGZmaqnyFiCFoHktjNbvpvF8WRpVLhEv KrYzILjhNYkhIYsHeDBCIeO461iCbnO827xVPOjDMBKgF6SFjpKlfcu86CVkESJbVR 3JFAjjII3dtZAbzNbK2fb9d1jpmpEr6SlsOPfi9iqBPLTLlGxNc4it3VxoA5kHyEuI vk/HT8NvfjNpQ== Date: Mon, 19 Jan 2026 12:32:47 +0000 From: Will Deacon To: Benjamin Gaignard 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 Subject: Re: [PATCH v11 3/7] iommu: Add verisilicon IOMMU driver Message-ID: References: <20260107101005.84039-1-benjamin.gaignard@collabora.com> <20260107101005.84039-4-benjamin.gaignard@collabora.com> <68a49f8b-178c-4fa2-b4a9-315ad602271d@collabora.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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... Will