In xlnx kernel version 2018.3 spi work fine on ultra96 LS connector
simple spidev_test -D /dev/spidev0.0 -pAbc command give expected spi waveform below
In 2020.1 kernel the CS is not driven the same way
same command give waveform below where cs polarity is obviously wrong
to get same or say expected behavior cs_high must be used that turn cs active low !
command is spidev_test -C -D /dev/spidev0.0 -p Abc
They were a lot of changes in between this version, cadence spi driver(likley ok) gpio bidning in dts
I think low polairty is the default a, existing appluication and drivers shall still work without changes
So i feel like something is wrong but what /where ?
notes :
-spidev_test is the tool provided as source in kernel tree /tools/spi
-spidev may have to be enabled in kernel conf
-dts is modified to get the 2 LS and HS spidev usable (this cause some ugly message as boot in 2020.1 kernel since spidev shall not be used in dts drielcty)
&spi0 { /* Low Speed connector */
spidev@0 {
compatible = "spidev" ;
spi-max-frequency = <10000000> ;
reg = <0> ;
};
};
&spi1 { /* High Speed connector */
spidev@0 {
compatible = "spidev" ;
spi-max-frequency = <10000000> ;
reg = <0> ;
};
};
