Re: [PATCH v3 4/4] arm64: dts: rockchip: Add devicetree for Pine64 PineTab2

[Manuel Traut <manut@mecka.net>]

Hi Jonas and Ondřej,

> >> +&sfc {
> >> +	pinctrl-names = "default";
> >> +	pinctrl-0 = <&fspi_dual_io_pins>;
> >> +	status = "okay";
> >> +	#address-cells = <1>;
> >> +	#size-cells = <0>;
> >> +
> >> +	flash@0 {
> >> +		compatible = "jedec,spi-nor";
> >> +		reg = <0>;
> >> +		spi-max-frequency = <24000000>;
> > 
> > That's a bit on the low side. The flash chip should work for all commands up to
> > 80MHz https://megous.com/dl/tmp/b428ad9b85ac4633.png and SGM3157YC6 switch
> > for the FSPI-CLK should have high enough bandwidth, too.
> 
> I agree that this is a little bit on the low side, it was a safe rate
> that I used for U-Boot. U-Boot required an exact rate of the supported
> sfc clk rates: 24, 50, 75, 100, 125 or 150 MHz.
> 
> Please also note that the SPI NOR flash chip used in PineTab2 is not a
> GigaDevice GD25LQ128E, it should be a SiliconKaiser SK25LP128, same as
> found in the Pine64 PinePhone Pro.

The schematics for v2.0 reference a GD25LQ128EWIGR. I never checked the jedec
id. How did you retrieve this information, or is it maybe a difference in v0.1
and 2.0?

> >> +		spi-rx-bus-width = <2>;
> > 
> > GD25LQ128E supports quad I/O. Maybe try 4 if it will work.
> 
> The schematic only shows fspi D0 and D1 connected, and use the D2 line
> for eMMC_RSTn, so spi-rx-bus-width = <2> should be correct.

ack

Since it is only needed for bootloader updates and environment its maybe better
to stay on the safe side?

But I can test faster frequency if you want me to do..

Regards
Manuel