Thanks Chuanhong, That is exactly what introduced the issue. I double check with and without the patch and without it I got the random data from mtd:
Without the patch target/linux/ath79/patches-4.14/461-spi-ath79-add-fast-flash-read.patch: root@OpenWrt:/# dd if=/dev/mtd4 | md5sum - d339cbfaf5ce709878d98bf83b853b63 - 7936+0 records in 7936+0 records out root@OpenWrt:/# dd if=/dev/mtd4 | md5sum - b97c976391ae881a8139f325a18ecdb2 - 7936+0 records in 7936+0 records out root@OpenWrt:/# uname -a Linux OpenWrt 4.14.167 #0 Mon Feb 3 15:18:08 2020 mips GNU/Linux With the patch target/linux/ath79/patches-4.14/461-spi-ath79-add-fast-flash-read.patch: root@OpenWrt:/# dd if=/dev/mtd4 | md5sum - 2404e891bd9e420fc4ec45e61cdd0ca9 - 7936+0 records in 7936+0 records out root@OpenWrt:/# dd if=/dev/mtd4 | md5sum - 2404e891bd9e420fc4ec45e61cdd0ca9 - 7936+0 records in 7936+0 records out root@OpenWrt:/# dd if=/dev/mtd4 | md5sum - 2404e891bd9e420fc4ec45e61cdd0ca9 - 7936+0 records in 7936+0 records out root@OpenWrt:/# uname -a Linux OpenWrt 4.14.167 #0 Mon Feb 3 15:18:08 2020 mips GNU/Linux Buildtime are equal... maybe it is because of some reproducibility effort that does not consider patches. All my tests are using initram image and kernel 4.14. The flash is a Spansion S25FL064PIF. It is the same of TL-WR842NDv1, which has the flash section of DTS identical. Kernel always detects it as: [ 0.656283] m25p80 spi0.0: s25sl064p (8192 Kbytes) I tried some random changes (without knowing what I'm really doing) like: compatible = "spansion,spi-nor"; compatible = "spansion,s25sl064p", "spansion,m25p80", "jedec,spi-nor" m25p,fast-read; But I guess all those name variations will, in the end, mean just the same. "m25p,fast-read" does not fix the issue as well. Regards, --- Luiz Angelo Daros de Luca luizl...@gmail.com Em qui., 6 de fev. de 2020 às 23:57, Chuanhong Guo <gch981...@gmail.com> escreveu: > Hi! > > On Fri, Feb 7, 2020 at 6:44 AM Luiz Angelo Daros de Luca > <luizl...@gmail.com> wrote: > > > > Hello, > > > > I isolated the problem to be kernel upgrade from 4.14 to 4.19. If I > build ath79 with 4.14, it simply works. > > The mtd problem also happens while booting 4.19 without touching the > flash 4.19 (using initram image). > > > > Flash reading is handled differently between 4.14 and 4.19. 4.14 reads > directly from 0x1f000000 where spi is mapped. But the interface used > for that got removed in 4.19 so bit-bang mode is used instead. > Could you try if removing > target/linux/ath79/patches-4.14/461-spi-ath79-add-fast-flash-read.patch > also breaks ath79/4.14? > > Regards, > Chuanhong Guo >
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