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

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Message-ID: <080c0900-4c34-e097-3e0e-4508951b0ddd@kernel.org>
Date:   Fri, 1 Feb 2019 09:13:03 -0600
From:   Dinh Nguyen <dinguyen@...nel.org>
To:     Simon Goldschmidt <simon.k.r.goldschmidt@...il.com>,
        Marek Vasut <marex@...x.de>
Cc:     devicetree@...r.kernel.org, linux-fpga@...r.kernel.org,
        linux-kernel@...r.kernel.org, Moritz Fischer <mdf@...nel.org>,
        Rob Herring <robh+dt@...nel.org>, Alan Tull <atull@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Russell King <linux@...linux.org.uk>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] ARM: socfpga: fix base address of SDR controller



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?

> On Wed, Jan 30, 2019 at 1:16 AM Dinh Nguyen <dinguyen@...nel.org> wrote:
>>
>>
>>
>> On 1/29/19 2:08 PM, Simon Goldschmidt wrote:
>>> From: Simon Goldschmidt <simon.k.r.goldschmidt@...il.com>
>>>
>>> The documentation for socfpga gen5 says the base address of the sdram
>>> controller is 0xffc20000, while the current devicetree says it is at
>>> 0xffc25000.
>>>
>>> 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@...il.com>
>>> ---
>>>
>>>  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@...25000 {
>>> +             sdr: sdr@...20000 {
>>>                       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.
> 
>>
>> [1]
>> https://www.intel.com/content/www/us/en/programmable/documentation/sfo1410143707420.html#sfo1411577366917
> 
> 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.

Dinh