linux-kernel - Re: [PATCH] arm64: dts: rockchip: Increase maximum frequency of SPI flash for ROCK Pi 4A/B/C

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Date: Fri, 15 Dec 2023 19:20:51 +0100
From: Dragan Simic <dsimic@...jaro.org>
To: Stefan Nagy <stefan.nagy@...psilon.net>
Cc: Heiko Stuebner <heiko@...ech.de>, linux-rockchip@...ts.infradead.org,
 linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: dts: rockchip: Increase maximum frequency of SPI
 flash for ROCK Pi 4A/B/C

On 2023-12-15 19:15, Dragan Simic wrote:
> On 2023-12-15 13:28, Stefan Nagy wrote:
>> The ROCK Pi 4A/B/C boards come with a 32 Mbit SPI NOR flash chip (XTX
>> Technology Limited XT25F32) which has a maximum clock frequency of 108
>> MHz. However, the Rockchip SPI controller driver limits the maximum
>> SPI clock frequency to 50 MHz. Use this limit for spi-max-freq.
>> 
>> This patch has been tested on ROCK Pi 4A.
>> 
>> Signed-off-by: Stefan Nagy <stefan.nagy@...psilon.net>
>> ---
>>  arch/arm64/boot/dts/rockchip/rk3399-rock-pi-4a.dts | 2 +-
>>  arch/arm64/boot/dts/rockchip/rk3399-rock-pi-4b.dts | 2 +-
>>  arch/arm64/boot/dts/rockchip/rk3399-rock-pi-4c.dts | 2 +-
>>  3 files changed, 3 insertions(+), 3 deletions(-)
>> 
>> diff --git a/arch/arm64/boot/dts/rockchip/rk3399-rock-pi-4a.dts
>> b/arch/arm64/boot/dts/rockchip/rk3399-rock-pi-4a.dts
>> index d5df8939a..30e63e62a 100644
>> --- a/arch/arm64/boot/dts/rockchip/rk3399-rock-pi-4a.dts
>> +++ b/arch/arm64/boot/dts/rockchip/rk3399-rock-pi-4a.dts
>> @@ -19,6 +19,6 @@ &spi1 {
>>  	flash@0 {
>>  		compatible = "jedec,spi-nor";
>>  		reg = <0>;
>> -		spi-max-frequency = <10000000>;
>> +		spi-max-frequency = <50000000>;
>>  	};
>>  };
>> diff --git a/arch/arm64/boot/dts/rockchip/rk3399-rock-pi-4b.dts
>> b/arch/arm64/boot/dts/rockchip/rk3399-rock-pi-4b.dts
>> index bee6d7588..7122bf6c0 100644
>> --- a/arch/arm64/boot/dts/rockchip/rk3399-rock-pi-4b.dts
>> +++ b/arch/arm64/boot/dts/rockchip/rk3399-rock-pi-4b.dts
>> @@ -37,7 +37,7 @@ &spi1 {
>>  	flash@0 {
>>  		compatible = "jedec,spi-nor";
>>  		reg = <0>;
>> -		spi-max-frequency = <10000000>;
>> +		spi-max-frequency = <50000000>;
>>  	};
>>  };
>> 
>> diff --git a/arch/arm64/boot/dts/rockchip/rk3399-rock-pi-4c.dts
>> b/arch/arm64/boot/dts/rockchip/rk3399-rock-pi-4c.dts
>> index de2ebe4cb..8af75bc7c 100644
>> --- a/arch/arm64/boot/dts/rockchip/rk3399-rock-pi-4c.dts
>> +++ b/arch/arm64/boot/dts/rockchip/rk3399-rock-pi-4c.dts
>> @@ -49,7 +49,7 @@ &spi1 {
>>  	flash@0 {
>>  		compatible = "jedec,spi-nor";
>>  		reg = <0>;
>> -		spi-max-frequency = <10000000>;
>> +		spi-max-frequency = <50000000>;
>>  	};
>>  };
> 
> It would be better to upstream these changes to the Linux kernel
> first, and then sync them back to U-Boot.

Oops, my bad, sorry, I got confused with your other patch on the U-Boot 
mailing list.

Regarding the new spi-max-frequency value, it should be better to have 
it set to what the SPI chip actually supports, and let the SPI driver do 
its thing.