linux-kernel - Re: [PATCH v2 3/3] ARM: dts: aspeed: asrock: Correct firmware flash SPI clocks

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Date:   Wed, 1 Mar 2023 08:33:58 +0100
From:   Cédric Le Goater <clg@...d.org>
To:     Joel Stanley <joel@....id.au>, Zev Weiss <zev@...ilderbeest.net>
CC:     Andrew Jeffery <andrew@...id.au>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Rob Herring <robh+dt@...nel.org>, <devicetree@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-aspeed@...ts.ozlabs.org>, <linux-kernel@...r.kernel.org>,
        <openbmc@...ts.ozlabs.org>, <stable@...r.kernel.org>
Subject: Re: [PATCH v2 3/3] ARM: dts: aspeed: asrock: Correct firmware flash
 SPI clocks

On 3/1/23 02:30, Joel Stanley wrote:
> On Fri, 24 Feb 2023 at 00:04, Zev Weiss <zev@...ilderbeest.net> wrote:
>>
>> While I'm not aware of any problems that have occurred running these
>> at 100 MHz, the official word from ASRock is that 50 MHz is the
>> correct speed to use, so let's be safe and use that instead.
> 
> :(
> 
> Validated with which driver?
> 
> Cédric, do you have any thoughts on this?
  

Transactions on the Firmware SPI controller are usually configured at
50MHz by U-Boot and Linux to stay on the safe side, specially CE0 from
which the board boots. The other SPI controllers are generally set at
a higher freq : 100MHz, because the devices on these buses are not for
booting the BMC, they are mostly only written to (at a default lower
freq). There are some exceptions when the devices and the wiring permit
higher rates.

For the record, we lowered the SPI freq on the AST2400 (palmetto)
because some chips would freak out once in a while at 100MHz.

C.

>> Signed-off-by: Zev Weiss <zev@...ilderbeest.net>
>> Cc: stable@...r.kernel.org
>> Fixes: 2b81613ce417 ("ARM: dts: aspeed: Add ASRock E3C246D4I BMC")
>> Fixes: a9a3d60b937a ("ARM: dts: aspeed: Add ASRock ROMED8HM3 BMC")
>> ---
>>   arch/arm/boot/dts/aspeed-bmc-asrock-e3c246d4i.dts | 2 +-
>>   arch/arm/boot/dts/aspeed-bmc-asrock-romed8hm3.dts | 2 +-
>>   2 files changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm/boot/dts/aspeed-bmc-asrock-e3c246d4i.dts b/arch/arm/boot/dts/aspeed-bmc-asrock-e3c246d4i.dts
>> index 67a75aeafc2b..c4b2efbfdf56 100644
>> --- a/arch/arm/boot/dts/aspeed-bmc-asrock-e3c246d4i.dts
>> +++ b/arch/arm/boot/dts/aspeed-bmc-asrock-e3c246d4i.dts
>> @@ -63,7 +63,7 @@ flash@0 {
>>                  status = "okay";
>>                  m25p,fast-read;
>>                  label = "bmc";
>> -               spi-max-frequency = <100000000>; /* 100 MHz */
>> +               spi-max-frequency = <50000000>; /* 50 MHz */
>>   #include "openbmc-flash-layout.dtsi"
>>          };
>>   };
>> diff --git a/arch/arm/boot/dts/aspeed-bmc-asrock-romed8hm3.dts b/arch/arm/boot/dts/aspeed-bmc-asrock-romed8hm3.dts
>> index 00efe1a93a69..4554abf0c7cd 100644
>> --- a/arch/arm/boot/dts/aspeed-bmc-asrock-romed8hm3.dts
>> +++ b/arch/arm/boot/dts/aspeed-bmc-asrock-romed8hm3.dts
>> @@ -51,7 +51,7 @@ flash@0 {
>>                  status = "okay";
>>                  m25p,fast-read;
>>                  label = "bmc";
>> -               spi-max-frequency = <100000000>; /* 100 MHz */
>> +               spi-max-frequency = <50000000>; /* 50 MHz */
>>   #include "openbmc-flash-layout-64.dtsi"
>>          };
>>   };
>> --
>> 2.39.1.438.gdcb075ea9396.dirty
>>