[openwrt/openwrt] ath79: increase spi frequency on TL-WDR3500/3600/4300/4310

[LEDE Commits]

adrian pushed a commit to openwrt/openwrt.git, branch master:
https://git.openwrt.org/37df722266a205c7bbbf333a67aad70253769f91

commit 37df722266a205c7bbbf333a67aad70253769f91
Author: Aleksander Jan Bajkowski <A.Bajkowski at stud.elka.pw.edu.pl>
AuthorDate: Sun Jul 19 10:07:24 2020 +0200

    ath79: increase spi frequency on TL-WDR3500/3600/4300/4310
    
    SPI Flash chip supports up to 33 MHz wihout fast read opcode.
    Available frequencies are 112.5, 56.25, 37.5, 28.125, 22.5 etc.
    This patch increases the nominal maximum frequency to 33 MHz,
    reaching an effective increase from 22.5 to 28.125 MHz.
    
    Formula to calculate SPI frequency:
    Freq = 225 MHz / 2 / div
    
    Before:
    
    $ time dd if=/dev/mtd1 of=/dev/null bs=8M
    0+1 records in
    0+1 records out
    real    0m 3.58s
    user    0m 0.00s
    sys     0m 3.57s
    
    After:
    
    $ time dd if=/dev/mtd1 of=/dev/null bs=8M
    0+1 records in
    0+1 records out
    real    0m 2.95s
    user    0m 0.00s
    sys     0m 2.93s
    
    Signed-off-by: Aleksander Jan Bajkowski <A.Bajkowski at stud.elka.pw.edu.pl>
    [minor commit message adjustments]
    Signed-off-by: Adrian Schmutzler <freifunk at adrianschmutzler.de>
---
 target/linux/ath79/dts/ar9344_tplink_tl-wdrxxxx.dtsi | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/target/linux/ath79/dts/ar9344_tplink_tl-wdrxxxx.dtsi b/target/linux/ath79/dts/ar9344_tplink_tl-wdrxxxx.dtsi
index 124f4d50b2..489408520e 100644
--- a/target/linux/ath79/dts/ar9344_tplink_tl-wdrxxxx.dtsi
+++ b/target/linux/ath79/dts/ar9344_tplink_tl-wdrxxxx.dtsi
@@ -78,7 +78,7 @@
 	flash at 0 {
 		compatible = "jedec,spi-nor";
 		reg = <0>;
-		spi-max-frequency = <25000000>;
+		spi-max-frequency = <33000000>;
 
 		partitions {
 			compatible = "fixed-partitions";