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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:autocrypt :message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=tF8uyKERWCoMyAnlRKqJDO1qWaCVQS8YdldPCqsx9S0=; b=RBtwYRutkEOlBl6kvmytGf9wQpgyt0fgGYLBBL/Fs2lXIF72/iGKEZ5lgXJNUjkgtW 33jukQXexPUy+xOZIz6enAghB43e9db4IHlRDAL/+jW6gx6ya/fpRv/OQt/V0QYskFiA QnlZBagPS16w9kt1TfpKK1kDW2UVlc/V7WONObgHj61Oxf0oYwxAK4mZH/i9DI9HAm/7 h53ZaRoUasJvzV95Rsz3X/L1HojUDl7RNHwuPKLkMJ0tKdZDttxDD5rhSoBqzN5uBnG0 ALx7fE4D+beHwpQ87DgvTt8ZB5meeBkWOYvVr0GuX7oHCXpqqSDf6TJY3ZXkDJ46a6Hf 3igQ== X-Gm-Message-State: AOAM530IeQFv4apPvgMnLZIcZnsJLhQ0+p5/p4cVkKX9ZIMxAgu5ygEO jkUpHhat8cetCCobBboiCbY= X-Google-Smtp-Source: ABdhPJyPo9ML0x66bHS+KgpIhpg94ojy5fT6fH9mQxG7FMKBoEYl0Sy3IFq3hGAQTn1h+1yxXOP42w== X-Received: by 2002:aa7:81d6:0:b029:19e:2987:7465 with SMTP id c22-20020aa781d60000b029019e29877465mr8761737pfn.29.1610650373721; Thu, 14 Jan 2021 10:52:53 -0800 (PST) Subject: Re: [RFC PATCH v3 6/6] of: Add plumbing for restricted DMA pool To: Claire Chang Cc: Rob Herring , mpe@ellerman.id.au, benh@kernel.crashing.org, paulus@samba.org, "list@263.net:IOMMU DRIVERS" , Joerg Roedel , joro@8bytes.org, will@kernel.org, Frank Rowand , Konrad Rzeszutek Wilk , boris.ostrovsky@oracle.com, jgross@suse.com, sstabellini@kernel.org, Christoph Hellwig , Marek Szyprowski , Robin Murphy , grant.likely@arm.com, xypron.glpk@gmx.de, Thierry Reding , mingo@kernel.org, bauerman@linux.ibm.com, peterz@infradead.org, Greg KH , Saravana Kannan , rafael.j.wysocki@intel.com, heikki.krogerus@linux.intel.com, Andy Shevchenko , rdunlap@infradead.org, dan.j.williams@intel.com, Bartosz Golaszewski , linux-devicetree , lkml , linuxppc-dev@lists.ozlabs.org, "list@263.net:IOMMU DRIVERS" , Joerg Roedel , iommu@lists.linux-foundation.org, xen-devel@lists.xenproject.org, Tomasz Figa , Nicolas Boichat References: <20210106034124.30560-1-tientzu@chromium.org> <20210106034124.30560-7-tientzu@chromium.org> <95e6dd76-5e18-e445-c351-19fba18f36de@gmail.com> From: Florian Fainelli Autocrypt: addr=f.fainelli@gmail.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit On 1/14/21 1:08 AM, Claire Chang wrote: > On Wed, Jan 13, 2021 at 7:48 AM Florian Fainelli wrote: >> >> On 1/5/21 7:41 PM, Claire Chang wrote: >>> If a device is not behind an IOMMU, we look up the device node and set >>> up the restricted DMA when the restricted-dma-pool is presented. >>> >>> Signed-off-by: Claire Chang >>> --- >> >> [snip] >> >>> +int of_dma_set_restricted_buffer(struct device *dev) >>> +{ >>> + struct device_node *node; >>> + int count, i; >>> + >>> + if (!dev->of_node) >>> + return 0; >>> + >>> + count = of_property_count_elems_of_size(dev->of_node, "memory-region", >>> + sizeof(phandle)); >> >> You could have an early check for count < 0, along with an error >> message, if that is deemed useful. >> >>> + for (i = 0; i < count; i++) { >>> + node = of_parse_phandle(dev->of_node, "memory-region", i); >>> + if (of_device_is_compatible(node, "restricted-dma-pool")) >> >> And you may want to add here an of_device_is_available(node). A platform >> that provides the Device Tree firmware and try to support multiple >> different SoCs may try to determine if an IOMMU is present, and if it >> is, it could be marking the restriced-dma-pool region with a 'status = >> "disabled"' property, or any variant of that scheme. > > This function is called only when there is no IOMMU present (check in > drivers/of/device.c). I can still add of_device_is_available(node) > here if you think it's helpful. I believe it is, since boot loader can have a shared Device Tree blob skeleton and do various adaptations based on the chip (that's what we do) and adding a status property is much simpler than insertion new nodes are run time. > >> >>> + return of_reserved_mem_device_init_by_idx( >>> + dev, dev->of_node, i); >> >> This does not seem to be supporting more than one memory region, did not >> you want something like instead: >> >> ret = of_reserved_mem_device_init_by_idx(...); >> if (ret) >> return ret; >> > > Yes. This implement only supports one restriced-dma-pool memory region > with the assumption that there is only one memory region with the > compatible string, restricted-dma-pool, in the dts. IIUC, it's similar > to shared-dma-pool. Then if here is such a known limitation it should be both documented and enforced here, you shouldn ot be iterating over all of the phandles that you find, stop at the first one and issue a warning if count > 1? -- Florian