| Message ID | 20201013060623.1711-2-thunder.leizhen@huawei.com |
|---|---|
| State | New |
| Headers | show |
| Series | eliminate two common errors reported by any yaml on arm64 | expand |
On Wed, Oct 14, 2020 at 5:15 AM Florian Fainelli <f.fainelli@gmail.com> wrote: > On 10/12/2020 11:06 PM, Zhen Lei wrote: > > stingray-usb.dtsi is finally included by three dts files: > > bcm958802a802x.dts, bcm958742k.dts and bcm958742t.dts. I searched all > > these three entire expanded dts files, and each of them contains only one > > dma-ranges. No conversion range is specified, so it cannot work properly. > > I think this property "dma-ranges" is added by mistake, just remove it. > > Otherwise, the following error will be reported when any YAML detection > > is performed on arm64. > > > > arch/arm64/boot/dts/broadcom/stingray/stingray-usb.dtsi:7.3-14: Warning \ > > (dma_ranges_format): /usb:dma-ranges: empty "dma-ranges" property but \ > > its #address-cells (1) differs from / (2) > > arch/arm64/boot/dts/broadcom/stingray/stingray-usb.dtsi:7.3-14: Warning \ > > (dma_ranges_format): /usb:dma-ranges: empty "dma-ranges" property but \ > > its #size-cells (1) differs from / (2) > > > > Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> > > This looks fine to me, Scott, Ray do you want to Ack this patch before I > take it? Does it mean that there are no devices on this bus that can do DMA? Usually there should be a dma-ranges property to identify that DMA is possible and what the limits are, though we have failed to enforce that. Also note that the #address-cells=<1> means that any device under this bus is assumed to only support 32-bit addressing, and DMA will have to go through a slow swiotlb in the absence of an IOMMU. Arnd
On 2020/10/14 15:38, Arnd Bergmann wrote: > On Wed, Oct 14, 2020 at 5:15 AM Florian Fainelli <f.fainelli@gmail.com> wrote: >> On 10/12/2020 11:06 PM, Zhen Lei wrote: >>> stingray-usb.dtsi is finally included by three dts files: >>> bcm958802a802x.dts, bcm958742k.dts and bcm958742t.dts. I searched all >>> these three entire expanded dts files, and each of them contains only one >>> dma-ranges. No conversion range is specified, so it cannot work properly. >>> I think this property "dma-ranges" is added by mistake, just remove it. >>> Otherwise, the following error will be reported when any YAML detection >>> is performed on arm64. >>> >>> arch/arm64/boot/dts/broadcom/stingray/stingray-usb.dtsi:7.3-14: Warning \ >>> (dma_ranges_format): /usb:dma-ranges: empty "dma-ranges" property but \ >>> its #address-cells (1) differs from / (2) >>> arch/arm64/boot/dts/broadcom/stingray/stingray-usb.dtsi:7.3-14: Warning \ >>> (dma_ranges_format): /usb:dma-ranges: empty "dma-ranges" property but \ >>> its #size-cells (1) differs from / (2) >>> >>> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> >> >> This looks fine to me, Scott, Ray do you want to Ack this patch before I >> take it? > > Does it mean that there are no devices on this bus that can do DMA? > > Usually there should be a dma-ranges property to identify that DMA > is possible and what the limits are, though we have failed to enforce > that. Documentation/devicetree/bindings/iommu/iommu.txt +79 When an "iommus" property is specified in a device tree node, the IOMMU will be used for address translation. If a "dma-ranges" property exists in the device's parent node it will be ignored. An exception to this rule is if the referenced IOMMU is disabled, in which case the "dma-ranges" property of the parent shall take effect. The dma-ranges is only required by IOMMU disabled case. And should exist in the parent node of IOMMU device. But this deleted dma-ranges is under the usb bus node. > > Also note that the #address-cells=<1> means that any device under > this bus is assumed to only support 32-bit addressing, and DMA will > have to go through a slow swiotlb in the absence of an IOMMU. The dma_alloc_coherent() will allocate memory with GFP_DMA32 flag and try the 0-4G first. The reserved swiotlb buffer memory is used only when the allocation failed. memory@80000000: device_type: ["memory"] reg: [[0x0, 0x80000000, 0x0, 0x80000000], [0x8, 0x80000000, 0x1, 0x80000000]] If this is the actual physical memory size, the #address-cells should be set to <1>. > > Arnd > > . >
On 2020/10/14 22:02, Arnd Bergmann wrote: > On Wed, Oct 14, 2020 at 3:36 PM Leizhen (ThunderTown) > <thunder.leizhen@huawei.com> wrote: >> On 2020/10/14 15:38, Arnd Bergmann wrote: >>> On Wed, Oct 14, 2020 at 5:15 AM Florian Fainelli <f.fainelli@gmail.com> wrote: >>>> On 10/12/2020 11:06 PM, Zhen Lei wrote: >>>>> stingray-usb.dtsi is finally included by three dts files: >>>>> bcm958802a802x.dts, bcm958742k.dts and bcm958742t.dts. I searched all >>>>> these three entire expanded dts files, and each of them contains only one >>>>> dma-ranges. No conversion range is specified, so it cannot work properly. >>>>> I think this property "dma-ranges" is added by mistake, just remove it. >>>>> Otherwise, the following error will be reported when any YAML detection >>>>> is performed on arm64. >>>>> >>>>> arch/arm64/boot/dts/broadcom/stingray/stingray-usb.dtsi:7.3-14: Warning \ >>>>> (dma_ranges_format): /usb:dma-ranges: empty "dma-ranges" property but \ >>>>> its #address-cells (1) differs from / (2) >>>>> arch/arm64/boot/dts/broadcom/stingray/stingray-usb.dtsi:7.3-14: Warning \ >>>>> (dma_ranges_format): /usb:dma-ranges: empty "dma-ranges" property but \ >>>>> its #size-cells (1) differs from / (2) >>>>> >>>>> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> >>>> >>>> This looks fine to me, Scott, Ray do you want to Ack this patch before I >>>> take it? >>> >>> Does it mean that there are no devices on this bus that can do DMA? >>> >>> Usually there should be a dma-ranges property to identify that DMA >>> is possible and what the limits are, though we have failed to enforce >>> that. >> >> Documentation/devicetree/bindings/iommu/iommu.txt +79 >> When an "iommus" property is specified in a device tree node, the IOMMU will >> be used for address translation. If a "dma-ranges" property exists in the >> device's parent node it will be ignored. An exception to this rule is if the >> referenced IOMMU is disabled, in which case the "dma-ranges" property of the >> parent shall take effect. >> >> The dma-ranges is only required by IOMMU disabled case. And should exist in >> the parent node of IOMMU device. But this deleted dma-ranges is under the usb >> bus node. > > The USB hosts here don't use an IOMMU though, right? Generally, USB devices are accessed through the IOMMU. However, even in this case, dma-ranges is not necessarily required. There are many examples of this in arch/arm64/boot/dts/. For example: arch/arm64/boot/dts/arm/juno.dt.yaml. Not sure, but maybe I found the answer. vi drivers/of/address.c +457 457 Thus we treat the absence of 458 * "ranges" as equivalent to an empty "ranges" property which means 459 * a 1:1 translation at that level. 466 * This quirk also applies for 'dma-ranges' which frequently exist in 467 * child nodes without 'dma-ranges' in the parent nodes. --RobH 475 if (ranges == NULL || rlen == 0) { 476 offset = of_read_number(addr, na); 477 memset(addr, 0, pna * 4); 478 pr_debug("empty ranges; 1:1 translation\n"); 479 goto finish; 480 } By the way: At first, I thought that these errors was detected by YAML. Now, I found that it was generated by "make dtbs". That's why it was reported by any YAML. Thus, the need to fix these errors is even more urgent. > >>> Also note that the #address-cells=<1> means that any device under >>> this bus is assumed to only support 32-bit addressing, and DMA will >>> have to go through a slow swiotlb in the absence of an IOMMU. >> >> The dma_alloc_coherent() will allocate memory with GFP_DMA32 flag and >> try the 0-4G first. The reserved swiotlb buffer memory is used only >> when the allocation failed. > > The swiotlb is primarily about the streaming mappings with dma_map_*(), > which has to copy all data sent to the device. dma_alloc_coherent() > is a rare operation and less impacted by DMA limitations. OK, I got it. > > Arnd > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > > . >
On 2020/10/16 15:06, Leizhen (ThunderTown) wrote: > > > On 2020/10/14 22:02, Arnd Bergmann wrote: >> On Wed, Oct 14, 2020 at 3:36 PM Leizhen (ThunderTown) >> <thunder.leizhen@huawei.com> wrote: >>> On 2020/10/14 15:38, Arnd Bergmann wrote: >>>> On Wed, Oct 14, 2020 at 5:15 AM Florian Fainelli <f.fainelli@gmail.com> wrote: >>>>> On 10/12/2020 11:06 PM, Zhen Lei wrote: >>>>>> stingray-usb.dtsi is finally included by three dts files: >>>>>> bcm958802a802x.dts, bcm958742k.dts and bcm958742t.dts. I searched all >>>>>> these three entire expanded dts files, and each of them contains only one >>>>>> dma-ranges. No conversion range is specified, so it cannot work properly. >>>>>> I think this property "dma-ranges" is added by mistake, just remove it. >>>>>> Otherwise, the following error will be reported when any YAML detection >>>>>> is performed on arm64. >>>>>> >>>>>> arch/arm64/boot/dts/broadcom/stingray/stingray-usb.dtsi:7.3-14: Warning \ >>>>>> (dma_ranges_format): /usb:dma-ranges: empty "dma-ranges" property but \ >>>>>> its #address-cells (1) differs from / (2) >>>>>> arch/arm64/boot/dts/broadcom/stingray/stingray-usb.dtsi:7.3-14: Warning \ >>>>>> (dma_ranges_format): /usb:dma-ranges: empty "dma-ranges" property but \ >>>>>> its #size-cells (1) differs from / (2) >>>>>> >>>>>> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> >>>>> >>>>> This looks fine to me, Scott, Ray do you want to Ack this patch before I >>>>> take it? >>>> >>>> Does it mean that there are no devices on this bus that can do DMA? >>>> >>>> Usually there should be a dma-ranges property to identify that DMA >>>> is possible and what the limits are, though we have failed to enforce >>>> that. >>> >>> Documentation/devicetree/bindings/iommu/iommu.txt +79 >>> When an "iommus" property is specified in a device tree node, the IOMMU will >>> be used for address translation. If a "dma-ranges" property exists in the >>> device's parent node it will be ignored. An exception to this rule is if the >>> referenced IOMMU is disabled, in which case the "dma-ranges" property of the >>> parent shall take effect. >>> >>> The dma-ranges is only required by IOMMU disabled case. And should exist in >>> the parent node of IOMMU device. But this deleted dma-ranges is under the usb >>> bus node. >> >> The USB hosts here don't use an IOMMU though, right? > > Generally, USB devices are accessed through the IOMMU. However, even in this > case, dma-ranges is not necessarily required. There are many examples of this > in arch/arm64/boot/dts/. For example: arch/arm64/boot/dts/arm/juno.dt.yaml. > > Not sure, but maybe I found the answer. > > vi drivers/of/address.c +457 > 457 Thus we treat the absence of > 458 * "ranges" as equivalent to an empty "ranges" property which means > 459 * a 1:1 translation at that level. > > 466 * This quirk also applies for 'dma-ranges' which frequently exist in > 467 * child nodes without 'dma-ranges' in the parent nodes. --RobH > > 475 if (ranges == NULL || rlen == 0) { > 476 offset = of_read_number(addr, na); > 477 memset(addr, 0, pna * 4); > 478 pr_debug("empty ranges; 1:1 translation\n"); > 479 goto finish; > 480 } > > By the way: At first, I thought that these errors was detected by YAML. Now, > I found that it was generated by "make dtbs". That's why it was reported by > any YAML. Thus, the need to fix these errors is even more urgent. > > >> >>>> Also note that the #address-cells=<1> means that any device under >>>> this bus is assumed to only support 32-bit addressing, and DMA will Hi, Arnd: I known what you mean now. I will rewrite the patch. Thanks. >>>> have to go through a slow swiotlb in the absence of an IOMMU. >>> >>> The dma_alloc_coherent() will allocate memory with GFP_DMA32 flag and >>> try the 0-4G first. The reserved swiotlb buffer memory is used only >>> when the allocation failed. >> >> The swiotlb is primarily about the streaming mappings with dma_map_*(), >> which has to copy all data sent to the device. dma_alloc_coherent() >> is a rare operation and less impacted by DMA limitations. > > OK, I got it. > >> >> Arnd >> >> _______________________________________________ >> linux-arm-kernel mailing list >> linux-arm-kernel@lists.infradead.org >> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >> >> . >> > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > > . >
diff --git a/arch/arm64/boot/dts/broadcom/stingray/stingray-usb.dtsi b/arch/arm64/boot/dts/broadcom/stingray/stingray-usb.dtsi index 55259f973b5a9e4..9ac8be6c65aa031 100644 --- a/arch/arm64/boot/dts/broadcom/stingray/stingray-usb.dtsi +++ b/arch/arm64/boot/dts/broadcom/stingray/stingray-usb.dtsi @@ -4,7 +4,6 @@ */ usb { compatible = "simple-bus"; - dma-ranges; #address-cells = <1>; #size-cells = <1>; ranges = <0x0 0x0 0x68500000 0x00400000>;
stingray-usb.dtsi is finally included by three dts files: bcm958802a802x.dts, bcm958742k.dts and bcm958742t.dts. I searched all these three entire expanded dts files, and each of them contains only one dma-ranges. No conversion range is specified, so it cannot work properly. I think this property "dma-ranges" is added by mistake, just remove it. Otherwise, the following error will be reported when any YAML detection is performed on arm64. arch/arm64/boot/dts/broadcom/stingray/stingray-usb.dtsi:7.3-14: Warning \ (dma_ranges_format): /usb:dma-ranges: empty "dma-ranges" property but \ its #address-cells (1) differs from / (2) arch/arm64/boot/dts/broadcom/stingray/stingray-usb.dtsi:7.3-14: Warning \ (dma_ranges_format): /usb:dma-ranges: empty "dma-ranges" property but \ its #size-cells (1) differs from / (2) Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> --- arch/arm64/boot/dts/broadcom/stingray/stingray-usb.dtsi | 1 - 1 file changed, 1 deletion(-) -- 1.8.3