From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Warren Date: Thu, 23 Jul 2015 13:30:00 -0600 Subject: [U-Boot] [PATCH V2 5/6] P2571: dts: Add DT files for Tegra210/P2571 board In-Reply-To: <4d71434af31143eb832c0f48b76bf2c2@HQMAIL103.nvidia.com> References: <1437421844-5157-1-git-send-email-twarren@nvidia.com> <1437421844-5157-6-git-send-email-twarren@nvidia.com> <55AFDE08.1080809@wwwdotorg.org> <517c2000505e4e27a712715786fb257f@HQMAIL103.nvidia.com> <55B12B9D.6000900@wwwdotorg.org> <4d71434af31143eb832c0f48b76bf2c2@HQMAIL103.nvidia.com> Message-ID: <55B140B8.2060301@wwwdotorg.org> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de On 07/23/2015 01:06 PM, Tom Warren wrote: > Stephen, > >> -----Original Message----- >> From: Stephen Warren [mailto:swarren at wwwdotorg.org] >> Sent: Thursday, July 23, 2015 11:00 AM >> To: Tom Warren >> Cc: u-boot at lists.denx.de; Thierry Reding; Stephen Warren; >> tomcwarren3959 at gmail.com >> Subject: Re: [U-Boot] [PATCH V2 5/6] P2571: dts: Add DT files for >> Tegra210/P2571 board >> >> On 07/23/2015 11:44 AM, Tom Warren wrote: >>> Stephen, >>> >>>> -----Original Message----- >>>> From: Stephen Warren [mailto:swarren at wwwdotorg.org] >>>> Sent: Wednesday, July 22, 2015 11:17 AM >>>> To: Tom Warren >>>> Cc: u-boot at lists.denx.de; Thierry Reding; Stephen Warren; >>>> tomcwarren3959 at gmail.com >>>> Subject: Re: [U-Boot] [PATCH V2 5/6] P2571: dts: Add DT files for >>>> Tegra210/P2571 board >>>> >>>> On 07/20/2015 01:50 PM, Tom Warren wrote: >>>>> Based on T124 Venice2. SDMMC1 is SD-card slot. >>>> >>>>> arch/arm/dts/{tegra124.dtsi => tegra210.dtsi} | 153 ++++----------------- >>>> >>>> There's also a lot of stuff in that file that isn't used in U-Boot or >>>> isn't validated yet (audio, SPI?, PWM, I2C?, APBDMA, PCIe). I'd >>>> suggest trimming the DT down to the absolute bare minimum for what >>>> U-Boot is using right now. That will help prevent any inconsistencies >>>> between the U-Boot and kernel DT files for Tegra210. >> > >>> Audio, PCIE make sense. UART and SPI both have DMA properties, so I can' t >> remove APBDMA. I'll do a cleanup run and see what shakes out. >> >> I believe the DMA properties should be optional in the bindings for UART and >> SPI. So, you should be able to remove the DMA properties from the client >> nodes and hence also the APBDMA node. (Especially given that the U-Boot >> drivers those HW blocks don't do DMA). > > If they're optional, why are they in tegra124.dtsi? (and T114 and T30). I wonder how they got in there originally? DMA is a useful feature, and all the bindings design work and testing for APBDMA has happened on earlier chips in order to enable DMA usage in the Linux kernel. Consequently, the DMA-related properties exist in the Linux kernel's copy of the DT. The whole point of a DT is that it's identical between all users of the DT. Consequently, (parts of I suspect) the DT file from the Linux kernel have been sync'd into U-Boot's copy of the DT, and hence the DMA properties showed up in U-Boot. For T210, we haven't yet validated that all the DMA related bindings/... are appropriate, so we shouldn't be adding them to /any/ copy of the DT yet, in case design/... changes are required. This will avoid adding incorrect content and then having to fix it later. Once DMA usage is validated in the kernel, and hence DMA-related properties are added to the kernel's copy of the DT, we should keep the nodes/properties in sync between the kernel and U-Boot just like earlier chips.