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

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Message-ID: <961ac9bf-d111-2e42-a39b-b26c499afcc0@kernel.org>
Date:   Wed, 30 Jan 2019 09:50:31 -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)
> 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.

That's great! Can you elaborate on what is the impetus for converting
the SDR driver to use the dts?

Dinh