Dear all,
I have tried to work with SPI1 on the beaglebone black (kernel 3.8) by
using spidev.
I saw several guides on that and so, I compiled my own device tree and it
works:
I can send and receive packet, change the spi clock frequency and so on.
This is my device tree file
/dts-v1/;
/plugin/;
/ {
compatible = "ti,beaglebone", "ti,beaglebone-black";
part-number = "BB-SPI1";
version = "00A0";
fragment@0 {
target = <&am33xx_pinmux>;
__overlay__ {
bone_replicape_spi1_pins: pinmux_replicape_spi1_pins {
pinctrl-single,pins = <
0x190 0x3B /* P9_31 =
mcasp0_aclkx.spi1_sclk , NO PULL | MODE3 */
0x194 0x3B /* P9_29 =
mcasp0_fsx.spi1_d0 , NO PULL | MODE3 */
0x198 0x1B /* P9_30 =
mcasp0_axr0.spi1_d1 , NO PULL | MODE3 */
0x19c 0x1B /* P9_28 =
mcasp0_ahclkr.spi1_cs0 , NO PULL | MODE3 */
0x164 0x0A /* P9_42 =
spi1_cs1 , NO PULL | MODE2 */
>;
};
};
};
fragment@1 {
target = <&spi1>;
__overlay__ {
#address-cells = <1>;
#size-cells = <0>;
status = "okay";
pinctrl-names = "default";
pinctrl-0 = <&bone_replicape_spi1_pins>;
cs-gpios = <&gpio4 17 0>, <&gpio1 7 0>;
cs0-device {
#address-cells = <1>;
#size-cells = <0>;
compatible = "spidev";
reg = <0>;
spi-max-frequency = <16000000>;
};
cs1-device {
#address-cells = <1>;
#size-cells = <0>;
compatible = "spidev";
reg = <1>;
spi-max-frequency = <16000000>;
};
};
};
};
Now I would like to go ahead and try to map it directly by mmap.
This is my C code:
#define SPI_BASE 0x481A0000 // SPI BASE Register
#define REGLEN 0x400
#define SPI_REVISION (0x000/4)
#define SPI_SYSCONFIG (0x110/4)
#define SPI_SYSSTATUS (0x114/4)
.....
.....
.....
.....
int main() {
volatile unsigned int *data = NULL;
volatile unsigned int *spi_addr = NULL;
int fd_gp = open("/dev/mem",O_RDWR);
spi_addr = mmap(NULL, REGLEN, PROT_READ | PROT_WRITE, MAP_SHARED,
fd_gp, SPI_BASE);
data = spi_addr + SPI_REVISION;
printf("SPI_REVISION value = 0x%x.\n",*data);
return 0;
}
As soon as I try to print the SPI_REVISION value, my program gets stuck.
I am quite sure I am doing a stupid error somewhere but I do not see where.
Can you help me?
Thanks.
Alberto
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