[PATCH] ramips: increase SPI frequency for MT7620 Archer

[mail at adrianschmutzler.de]

> -----Original Message-----
> From: David Bauer [mailto:mail at david-bauer.net]
> Sent: Mittwoch, 22. Juli 2020 14:21
> To: mail at adrianschmutzler.de
> Cc: openwrt-devel at lists.openwrt.org
> Subject: Re: [PATCH] ramips: increase SPI frequency for MT7620 Archer
> 
> Hello Adrian,
> 
> On 7/22/20 11:29 AM, mail at adrianschmutzler.de wrote:
> >> -----Original Message-----
> >> From: openwrt-devel [mailto:openwrt-devel-
> bounces at lists.openwrt.org]
> >> On Behalf Of David Bauer
> >> Sent: Dienstag, 21. Juli 2020 23:40
> >> To: openwrt-devel at lists.openwrt.org
> >> Subject: [PATCH] ramips: increase SPI frequency for MT7620 Archer
> >>
> >> Increase the SPI frequency for the MT7620 based TP-Link Archer series
> >> to 30MHz.
> >
> > Acked-by: Adrian Schmutzler <freifunk at adrianschmutzler.de>
> >
> > I'm not sure which are the frequency steps actually observed on that
> target, but raising it above the abundant copy/pasted 10 MHz seems a good
> idea in any case.
> 
> The SPI master can be operated in a range of {2..128}/SYS_CLK. (2..128 has to
> be power of two). So in the end it will transfer at around 18 MHz.
> 
> I don't want to crank this up further, as TP-Link uses a broad selection of SPI
> chips on a single hardware revision on many of their devices.
> Increasing performance might come at the cost of compatibility here.

Yes, no objection.

I just asked in case the next step would have been close, e.g. 33 MHz, then one could have thought about raising it a little more.

But I'm fine with anything faster than the 10 Mhz :-)

Best

Adrian

> 
> Best wishes
> David
> 
> >
> > Best
> >
> > Adrian
> >
> >>
> >> TP-Link uses different SPI flash chips for the same board revision,
> >> so be conservative to not break boards with a different chip. 30MHz
> >> should be well supported by all chips.
> >>
> >> Tested on Archer C2 v1 (GD25Q64B) and Archer C20i (W25Q64FV).
> >>
> >> Archer C20i (before)
> >> ====================
> >> root at OpenWrt:~# time dd if=/dev/mtd1 of=/tmp/test.bin bs=64k
> >> 122+0 records in
> >> 122+0 records out
> >> real	0m 15.30s
> >> user	0m 0.00s
> >> sys	0m 15.29s
> >>
> >> Archer C20i (after)
> >> ===================
> >> root at OpenWrt:~# time dd if=/dev/mtd1 of=/tmp/test.bin bs=64k
> >> 122+0 records in
> >> 122+0 records out
> >> real	0m 5.99s
> >> user	0m 0.00s
> >> sys	0m 5.98s
> >>
> >> Signed-off-by: David Bauer <mail at david-bauer.net>
> >> ---
> >>   target/linux/ramips/dts/mt7620a_tplink_archer-c2-v1.dts | 2 +-
> >> target/linux/ramips/dts/mt7620a_tplink_archer-mr200.dts | 2 +-
> >>   target/linux/ramips/dts/mt7620a_tplink_archer.dtsi      | 2 +-
> >>   3 files changed, 3 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/target/linux/ramips/dts/mt7620a_tplink_archer-c2-v1.dts
> >> b/target/linux/ramips/dts/mt7620a_tplink_archer-c2-v1.dts
> >> index c0b2c1ae92..75ddc5fb5d 100644
> >> --- a/target/linux/ramips/dts/mt7620a_tplink_archer-c2-v1.dts
> >> +++ b/target/linux/ramips/dts/mt7620a_tplink_archer-c2-v1.dts
> >> @@ -82,7 +82,7 @@
> >>   	flash at 0 {
> >>   		compatible = "jedec,spi-nor";
> >>   		reg = <0>;
> >> -		spi-max-frequency = <10000000>;
> >> +		spi-max-frequency = <30000000>;
> >>
> >>   		partitions {
> >>   			compatible = "fixed-partitions"; diff --git
> >> a/target/linux/ramips/dts/mt7620a_tplink_archer-mr200.dts
> >> b/target/linux/ramips/dts/mt7620a_tplink_archer-mr200.dts
> >> index c3c0efdfe6..0c0f4bb8e9 100644
> >> --- a/target/linux/ramips/dts/mt7620a_tplink_archer-mr200.dts
> >> +++ b/target/linux/ramips/dts/mt7620a_tplink_archer-mr200.dts
> >> @@ -121,7 +121,7 @@
> >>   	flash at 0 {
> >>   		compatible = "jedec,spi-nor";
> >>   		reg = <0>;
> >> -		spi-max-frequency = <10000000>;
> >> +		spi-max-frequency = <30000000>;
> >>
> >>   		partitions {
> >>   			compatible = "fixed-partitions"; diff --git
> >> a/target/linux/ramips/dts/mt7620a_tplink_archer.dtsi
> >> b/target/linux/ramips/dts/mt7620a_tplink_archer.dtsi
> >> index 184627b9f4..670bad615d 100644
> >> --- a/target/linux/ramips/dts/mt7620a_tplink_archer.dtsi
> >> +++ b/target/linux/ramips/dts/mt7620a_tplink_archer.dtsi
> >> @@ -43,7 +43,7 @@
> >>   	flash at 0 {
> >>   		compatible = "jedec,spi-nor";
> >>   		reg = <0>;
> >> -		spi-max-frequency = <10000000>;
> >> +		spi-max-frequency = <30000000>;
> >>
> >>   		partitions {
> >>   			compatible = "fixed-partitions";
> >> --
> >> 2.27.0
> >>
> >>
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> >>
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