Even I have the same problem, did you figure out why?
On Monday, November 6, 2017 at 9:57:17 AM UTC-6, simo zz wrote:
>
>
> Hello,
>
> I am developing a C application to read from the SPI0 from the Beaglebone
> Black.
>
> The test I am doing is with two Beaglebones, one configured as a slave
> which transmits data, and the other I want to act as slave.
>
> Both run a kernel *4.4.20-ti-r43*. The master it's working fine, but the
> slave it doesn't. The connection diagram I planned is attached as an image.
>
> The device-tree for the slave Beaglebone Black is the following:
>
> */dts-v1/;*
>
> */ {*
> * compatible = "ti,beaglebone", "ti,beaglebone-black",
> "ti,beaglebone-green";*
> * part-number = "BB-SPIDEV0";*
> * version = "00A0";*
> * exclusive-use = "P9.17", "P9.18", "P9.21", "P9.22", "spi0";*
>
> * fragment@0 {*
> * target = <0xdeadbeef>;*
>
> * __overlay__ {*
>
> * pinmux_bb_spi0_pins {*
> * pinctrl-single,pins = <*
> * 0x150 0x30 /* CLK INPUT */*
> * 0x154 0x30 /* DSO INPUT */ *
> * 0x158 0x10 /* DS1 OUTPUT */*
> * 0x15c 0x30 /* CS0 INPUT */*
> * >;*
> * linux,phandle = <0x1>;*
> * phandle = <0x1>;*
> * };*
> * };*
> * };*
>
> * fragment@1 {*
> * target = <0xdeadbeef>;*
>
> * __overlay__ {*
> * #address-cells = <0x1>;*
> * #size-cells = <0x0>;*
> * status = "okay";*
> * pinctrl-names = "default";*
> * pinctrl-0 = <0x1>;*
> * ti,pio-mode;*
>
> * channel@0 {*
> * #address-cells = <0x1>;*
> * #size-cells = <0x0>;*
> * compatible = "spidev";*
> * reg = <0x0>;*
> * spi-max-frequency = <0xf42400>;*
> * spi-cpha;*
> * };*
>
> * channel@1 {*
> * #address-cells = <0x1>;*
> * #size-cells = <0x0>;*
> * compatible = "spidev";*
> * reg = <0x1>;*
> * spi-max-frequency = <0xf42400>;*
> * };*
> * };*
> * };*
>
> * __symbols__ {*
> * bb_spi0_pins = "/fragment@0/__overlay__/pinmux_bb_spi0_pins";*
> * };*
>
> * __local_fixups__ {*
>
> * fragment@1 {*
>
> * __overlay__ {*
> * pinctrl-0 = <0x0>;*
> * };*
> * };*
> * };*
>
> * __fixups__ {*
> * am33xx_pinmux = "/fragment@0:target:0";*
> * spi0 = "/fragment@1:target:0";*
> * };*
> *};*
>
> and the C code used to read from the SPI is the following
>
> *#include <stdint.h>*
> *#include <unistd.h>*
> *#include <stdio.h>*
> *#include <stdlib.h>*
> *#include <string.h>*
> *#include <getopt.h>*
> *#include <fcntl.h>*
> *#include <libgen.h>*
> *#include <sys/ioctl.h>*
> *#include <sys/stat.h>*
> *#include <linux/types.h>*
> *#include <linux/spi/spidev.h>*
>
> *void pabort(char *string)*
> *{*
> * perror(string);*
> * abort();*
> *}*
>
> *void usage(char *progname)*
> *{*
> * printf("usage: %s <device> \n", progname);*
> *}*
>
> *void spiRead(int fd, uint32_t *rxbuffer, uint8_t bits, size_t txlen,
> uint32_t spiSpeed)*
> *{*
> * *rxbuffer = 0;*
>
> * struct spi_ioc_transfer tr =*
> * {*
> * .tx_buf = (uint32_t) 0,*
> * .rx_buf = (uint32_t) rxbuffer,*
> * .len = txlen,*
> * .delay_usecs = 1,*
> * .speed_hz = spiSpeed,*
> * .bits_per_word = bits,*
> * };*
>
> * if(ioctl(fd, SPI_IOC_MESSAGE(1), &tr) == -1)*
> * {*
> * perror("can't read SPI message");*
> * return;*
> * }*
> * else*
> * printf("SPI read: %x\n", *rxbuffer);*
>
> *}*
>
> *int main(int argc, char **argv)*
> *{*
> * int spifd = 0;*
> * uint8_t mode = 3;*
> * uint8_t bits = 32;*
> * uint32_t speed = 500000;*
> * uint32_t rxVal = 0;*
>
> * close(spifd);*
> * spifd = open("/dev/spidev1.0", O_RDWR);*
> * if(spifd == -1)*
> * {*
> * close(spifd);*
> * pabort("open: ");*
> * }*
>
> * if(ioctl(spifd, SPI_IOC_WR_MODE, &mode) == -1)*
> * pabort("ioctl SPI_IOC_WR_MODE: ");*
>
> * if(ioctl(spifd, SPI_IOC_WR_BITS_PER_WORD, &bits))*
> * pabort("ioctl SPI_IOC_WR_BITS_PER_WORD: ");*
>
> * if(ioctl(spifd, SPI_IOC_WR_MAX_SPEED_HZ, &speed))*
> * pabort("ioctl SPI_IOC_WR_MAX_SPEED_HZ: ");*
>
> * while(1)*
> * {*
> * // printf("Sending message to %s\n", argv[1]);*
>
> * spiRead(spifd, &rxVal, bits, sizeof(rxVal), speed);*
> * // usleep(500000);*
> * }*
>
> * close(spifd);*
>
> * return 0;*
> *}*
>
> However, the value read into rxBuffer is always *0xffffffff* and from the
> SPI0_SCLK pin I can see the clock signal (through my oscilloscope) so the
> CLK pin is not set as input as device-tree source should configure.
>
> From AM335x Technical Reference Manual, the SPI0 can be configured as
> Master and as Slave.
> What's wrong in my setup or what is the additional setting I have to do to
> have the SPI working as slave ?
>
> Thank you in advance.
> Regards,
> Simon
>
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