On 07/23/2015 01:06 PM, Tom Warren wrote:
Stephen,
-----Original Message-----
From: Stephen Warren [mailto:swar...@wwwdotorg.org]
Sent: Thursday, July 23, 2015 11:00 AM
To: Tom Warren
Cc: u-boot@lists.denx.de; Thierry Reding; Stephen Warren;
tomcwarren3...@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:swar...@wwwdotorg.org]
Sent: Wednesday, July 22, 2015 11:17 AM
To: Tom Warren
Cc: u-boot@lists.denx.de; Thierry Reding; Stephen Warren;
tomcwarren3...@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.
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