From mboxrd@z Thu Jan 1 00:00:00 1970 From: Grygorii Strashko Subject: [RESEND PATCH v2] dt/documentation: add specification of dma bus information Date: Wed, 24 Sep 2014 17:37:24 +0300 Message-ID: <1411569444-7567-1-git-send-email-grygorii.strashko@ti.com> Mime-Version: 1.0 Content-Type: text/plain Return-path: Sender: linux-kernel-owner@vger.kernel.org To: santosh.shilimkar@ti.com, Rob Herring Cc: devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux@arm.linux.org.uk, linux-kernel@vger.kernel.org, Arnd Bergmann , Grant Likely , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , Grygorii Strashko List-Id: devicetree@vger.kernel.org From: Santosh Shilimkar Recently we introduced the generic device tree infrastructure for couple of DMA bus parameter, dma-ranges and dma-coherent. Update the documentation so that its useful for future users. The "dma-ranges" property is intended to be used for describing the configuration of DMA bus RAM addresses and its offset w.r.t CPU addresses. The "dma-coherent" property is intended to be used for identifying devices supported coherent DMA operations. Cc: Arnd Bergmann Cc: Grant Likely Cc: Rob Herring Cc: Pawel Moll Cc: Mark Rutland Cc: Ian Campbell Cc: Kumar Gala Acked-by: Shawn Guo Signed-off-by: Grygorii Strashko Signed-off-by: Santosh Shilimkar --- Hi Rob, Seems, this patch has not been merged accidentally, so I've rebased it on top of Linux 3.17-rc5. Link on v1: https://lkml.org/lkml/2014/6/5/558 Documentation/devicetree/booting-without-of.txt | 53 +++++++++++++++++++++++++ 1 file changed, 53 insertions(+) diff --git a/Documentation/devicetree/booting-without-of.txt b/Documentation/devicetree/booting-without-of.txt index 1f013bd..7768518 100644 --- a/Documentation/devicetree/booting-without-of.txt +++ b/Documentation/devicetree/booting-without-of.txt @@ -51,6 +51,8 @@ Table of Contents VIII - Specifying device power management information (sleep property) + IX - Specifying dma bus information + Appendix A - Sample SOC node for MPC8540 @@ -1332,6 +1334,57 @@ reasonably grouped in this manner, then create a virtual sleep controller (similar to an interrupt nexus, except that defining a standardized sleep-map should wait until its necessity is demonstrated). +IX - Specifying dma bus information + +Some devices may have DMA memory range shifted relatively to the beginning of +RAM, or even placed outside of kernel RAM. For example, the Keystone 2 SoC +worked in LPAE mode with 4G memory has: +- RAM range: [0x8 0000 0000, 0x8 FFFF FFFF] +- DMA range: [ 0x8000 0000, 0xFFFF FFFF] +and DMA range is aliased into first 2G of RAM in HW. + +In such cases, DMA addresses translation should be performed between CPU phys +and DMA addresses. The "dma-ranges" property is intended to be used +for describing the configuration of such system in DT. + +In addition, each DMA master device on the DMA bus may or may not support +coherent DMA operations. The "dma-coherent" property is intended to be used +for identifying devices supported coherent DMA operations in DT. + +* DMA Bus master +Optional property: +- dma-ranges: encoded as arbitrary number of triplets of + (child-bus-address, parent-bus-address, length). Each triplet specified + describes a contiguous DMA address range. + The dma-ranges property is used to describe the direct memory access (DMA) + structure of a memory-mapped bus whose device tree parent can be accessed + from DMA operations originating from the bus. It provides a means of + defining a mapping or translation between the physical address space of + the bus and the physical address space of the parent of the bus. + (for more information see ePAPR specification) + +* DMA Bus child +Optional property: +- dma-ranges: value. if present - It means that DMA addresses + translation has to be enabled for this device. +- dma-coherent: Present if dma operations are coherent + +Example: +soc { + compatible = "ti,keystone","simple-bus"; + ranges = <0x0 0x0 0x0 0xc0000000>; + dma-ranges = <0x80000000 0x8 0x00000000 0x80000000>; + + [...] + + usb: usb@2680000 { + compatible = "ti,keystone-dwc3"; + + [...] + dma-coherent; + }; +}; + Appendix A - Sample SOC node for MPC8540 ======================================== -- 1.9.1