Re: [PATCH] ARM: socfpga: fix base address of SDR controller

From: Simon Goldschmidt
Date: Fri Feb 01 2019 - 10:50:37 EST

Am 01.02.2019 um 16:13 schrieb Dinh Nguyen:

On 1/30/19 12:00 AM, Simon Goldschmidt wrote:
+ Marek (as I really want to keep the dts in Linux and U-Boot in sync)

So can you wait until your patch in U-Boot is in?

Well, yes, this could wait. The problem is we wanted to keep Linux and U-Boot dts in sync.

I guess I'll just finish preparing my patch for U-Boot changing the dts there and then we'll see which part gets pushed first...

On Wed, Jan 30, 2019 at 1:16 AM Dinh Nguyen <dinguyen@xxxxxxxxxx> wrote:

On 1/29/19 2:08 PM, Simon Goldschmidt wrote:
From: Simon Goldschmidt <simon.k.r.goldschmidt@xxxxxxxxx>

The documentation for socfpga gen5 says the base address of the sdram
controller is 0xffc20000, while the current devicetree says it is at

While this is not a problem for Linux, as it only accesses the registers
above 0xffc25000, it *is* a problem for U-Boot because the lower registers
are used during DDR calibration (up to now, the U-Boot driver does not use
the dts address, but that should change).

To keep Linux and U-Boot devicetrees in sync, this patch changes the base
address to 0xffc20000 and adapts the 2 files where it is currently used.

This patch changes the dts and 2 drivers with one commit to prevent
breaking the code if dts change and driver change would be split.

Signed-off-by: Simon Goldschmidt <simon.k.r.goldschmidt@xxxxxxxxx>

arch/arm/boot/dts/socfpga.dtsi | 4 ++--
arch/arm/mach-socfpga/self-refresh.S | 4 ++--
drivers/fpga/altera-fpga2sdram.c | 2 +-
3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/arm/boot/dts/socfpga.dtsi b/arch/arm/boot/dts/socfpga.dtsi
index f365003f0..8f6c1a5d6 100644
--- a/arch/arm/boot/dts/socfpga.dtsi
+++ b/arch/arm/boot/dts/socfpga.dtsi
@@ -788,9 +788,9 @@
reg = <0xfffec000 0x100>;

- sdr: sdr@ffc25000 {
+ sdr: sdr@ffc20000 {
compatible = "altr,sdr-ctl", "syscon";
- reg = <0xffc25000 0x1000>;
+ reg = <0xffc20000 0x6000>;

I don't see the U-Boot device tree having this change. Yes, the
documentation does state that the SDR address starts at 0xffc20000, but
all of the pertinent registers start at 0x5000 offset. Thus, the
starting address should be 0xffc25000.[1]

You don't see it in U-Boot as I'm working on a patch for that.
As I wrote in the commit message, U-Boot currently does not use the
devicetree for the SDR driver, but I want to convert it to do that.

But before converting, I need to find a clean way to provide the
register addresses to the driver. That doesn't work with the current dts.


Well, in [2], you see that the peripheral's address range actually starts
at 0xffc20000. It's only the public documented registers that start at
0xffc25000. I don't know why the lower address range is undocumented.
Maybe you can help me here?

Yes, the reason these register are not documented is that the ddr
engineers didn't really want anyone outside of their team messing around
with the calibration. These registers, from the limited documentation I
have, are related to the PHY settings. I've been told the calibration
sequence is something of a "black" magic.

That's exactly how I thought it would be. However, that's not the best attitued for getting code into an open source project like U-Boot. For example, I wanted to take a look at the code to see if it can be made smaller, but that's unnecessary hard if the registers are not documented...