SPIdev

The SPI bus (or Serial Peripheral Interface bus) is a synchronous serial data link originally created by motorola.

For more information about SPI please refer to this link: http://en.wikipedia.org/wiki/Serial_Peripheral_Interface

In the linux kernel the SPI works only in master mode.

There is a way of using the spi kernel driver to work as a device in the userspace. It's called SPIdev.

=Configuring your kernel= For using it you will have to enable this options in your defconfig or manually in your kernel:

CONFIG_SPI_SUN4I=y

CONFIG_SPI_SUN6I=y

CONFIG_SPI=y

CONFIG_SPI_MASTER=y

CONFIG_EXPERIMENTAL=y

CONFIG_SPI_SPIDEV=y

=More information= For more information about using SPIdev in the userspace please refer to (Documentation/spi/): http://lxr.free-electrons.com/source/Documentation/spi/

You will find there:

spidev (contains the documentantion about the spidev)

spidev_fdx.c (contains a simple example in C of a full duplex communication)

spidev_test.c (contains a simple example in C of a half duplex communication)

=Configuring your FEX= It is important to configure your .fex file to be able to do so:

(if you are using spi0)

 [spi0_para] spi_used = 1 spi_cs_bitmap = 1 spi_cs0 = port:PI10<2> spi_sclk = port:PI11<2> spi_mosi = port:PI12<2> spi_miso = port:PI13<2> (here you will specify the number of spi devices your card will have, if you plan only to use the spidev just put 1):  [spi_devices] spi_dev_num = 1 (here you will have to put in the modalias "spidev")  [spi_board0] modalias = "spidev" max_speed_hz = 12000000 bus_num = 0 chip_select = 0 mode = 0 full_duplex = 1 manual_cs = 0 For more information about editing the fex file: http://linux-sunxi.org/Fex_Guide

=Configuring your DT (mainline)= Example for A10s Olinuxino Micro UEXT connector: --- a/arch/arm/boot/dts/sun5i-a10s.dtsi +++ b/arch/arm/boot/dts/sun5i-a10s.dtsi @@ -154,6 +154,20 @@                       clocks = <&apb1_gates 18>; status = "disabled"; }; + +              spi2: spi@01c17000 { +                      compatible = "allwinner,sun4i-a10-spi"; +                      reg = ; +                      interrupts = <12>; +                      clocks = <&ahb_gates 22>, <&spi2_clk>; +                      clock-names = "ahb", "mod"; +                      dmas = <&dma SUN4I_DMA_DEDICATED 29>, +                             <&dma SUN4I_DMA_DEDICATED 28>; +                      dma-names = "rx", "tx"; +                      status = "disabled"; +                      #address-cells = <1>; +                      #size-cells = <0>; +              };        }; }; @@ -198,4 +212,18 @@                allwinner,drive = ; allwinner,pull = ; }; + +      spi2_pins_a: spi2@0 { +              allwinner,pins = "PB11", "PB12", "PB13", "PB14"; +              allwinner,function = "spi2"; +              allwinner,drive = ; +              allwinner,pull = ; +      }; + +       spi2_pins_b: spi2@1 { +              allwinner,pins = "PE00", "PE01", "PE02", "PE03"; +              allwinner,function = "spi2"; +              allwinner,drive = ; +              allwinner,pull = ; +      }; };

--- a/arch/arm/boot/dts/sun5i-a10s-olinuxino-micro.dts +++ b/arch/arm/boot/dts/sun5i-a10s-olinuxino-micro.dts @@ -182,6 +188,12 @@       status = "okay"; }; +&spi2 { +      pinctrl-names = "default"; +      pinctrl-0 = <&spi2_pins_a>; +      status = "okay"; +}; + &ohci0 { status = "okay"; };

--- a/arch/arm/boot/dts/sun5i-a10s-olinuxino-micro.dts +++ b/arch/arm/boot/dts/sun5i-a10s-olinuxino-micro.dts @@ -192,6 +192,15 @@       pinctrl-names = "default"; pinctrl-0 = <&spi2_pins_a>; status = "okay"; +      spi2_0 { +              #address-cells = <1>; +              #size-cells = <0>; + +              compatible = "spidev"; + +              reg = <0>; +              spi-max-frequency = ; +      }; }; &ohci0 { =Using the SPI bus= Once you will have this set you can boot your sunxi device and you will have in your dev in /dev/spidevn.0

Transfer size is limited to 64 bytes on sun4i and 128 bytes on sun6i. You have to loop over longer messages in your code. Some SPI devices may require that you prefix each message fragment with a header, other may not. YMMV. Look up transfer diagrams in device datasheet.

Known problems: Using the spidev_test.c example you will receive [spi]: drivers/spi/spi_sunxi.c(L1025) cpu tx data time out!

Using the spidev_fdx.c method it works like a charm! :)

I've made a user friendlier library (C functions) to comunicate using SPIdev:

(Note, this library supose the read and write address to be 2 bytes)  /*   spidevlib.c - A user-space program to comunicate using spidev. Gustavo Zamboni
 * 1) include 
 * 2) include 
 * 3) include 
 * 4) include 
 * 5) include 
 * 6) include 
 * 7) include <sys/ioctl.h>
 * 8) include <linux/types.h>
 * 9) include <linux/spi/spidev.h>
 * 1) include <linux/spi/spidev.h>

char buf[10]; char buf2[10]; extern int com_serial; extern int failcount;

struct spi_ioc_transfer xfer[2];

////////// // Init SPIdev ////////// int spi_init(char filename[40]) {   	int file; __u8	mode, lsb, bits; __u32 speed=2500000;

if ((file = open(filename,O_RDWR)) < 0) {       	printf("Failed to open the bus."); /* ERROR HANDLING; you can check errno to see what went wrong */ com_serial=0; exit(1); }

///////////////		// Verifications ///////////////		//possible modes: mode |= SPI_LOOP; mode |= SPI_CPHA; mode |= SPI_CPOL; mode |= SPI_LSB_FIRST; mode |= SPI_CS_HIGH; mode |= SPI_3WIRE; mode |= SPI_NO_CS; mode |= SPI_READY; //multiple possibilities using | /*			if (ioctl(file, SPI_IOC_WR_MODE, &mode)<0)	{ perror("can't set spi mode"); return; }		*/

if (ioctl(file, SPI_IOC_RD_MODE, &mode) < 0) {				perror("SPI rd_mode"); return; }			if (ioctl(file, SPI_IOC_RD_LSB_FIRST, &lsb) < 0) {				perror("SPI rd_lsb_fist"); return; }		//sunxi supports only 8 bits /*			if (ioctl(file, SPI_IOC_WR_BITS_PER_WORD, 8)<0) {				perror("can't set bits per word"); return; }		*/			if (ioctl(file, SPI_IOC_RD_BITS_PER_WORD, &bits) < 0) {				perror("SPI bits_per_word"); return; }		/*			if (ioctl(file, SPI_IOC_WR_MAX_SPEED_HZ, &speed)<0) {				perror("can't set max speed hz"); return; }		*/			if (ioctl(file, SPI_IOC_RD_MAX_SPEED_HZ, &speed) < 0) {				perror("SPI max_speed_hz"); return; }

printf("%s: spi mode %d, %d bits %sper word, %d Hz max\n",filename, mode, bits, lsb ? "(lsb first) " : "", speed);

//xfer[0].tx_buf = (unsigned long)buf; xfer[0].len = 3; /* Length of command to write*/ xfer[0].cs_change = 0; /* Keep CS activated */ xfer[0].delay_usecs = 0, //delay in us	xfer[0].speed_hz = 2500000, //speed xfer[0].bits_per_word = 8, // bites per word 8

//xfer[1].rx_buf = (unsigned long) buf2; xfer[1].len = 4; /* Length of Data to read */ xfer[1].cs_change = 0; /* Keep CS activated */ xfer[0].delay_usecs = 0; xfer[0].speed_hz = 2500000; xfer[0].bits_per_word = 8;

return file; }

////////// // Read n bytes from the 2 bytes add1 add2 address //////////

char * spi_read(int add1,int add2,int nbytes,int file) {	int status;

memset(buf, 0, sizeof buf); memset(buf2, 0, sizeof buf2); buf[0] = 0x01; buf[1] = add1; buf[2] = add2; xfer[0].tx_buf = (unsigned long)buf; xfer[0].len = 3; /* Length of command to write*/ xfer[1].rx_buf = (unsigned long) buf2; xfer[1].len = nbytes; /* Length of Data to read */ status = ioctl(file, SPI_IOC_MESSAGE(2), xfer); if (status < 0) {		perror("SPI_IOC_MESSAGE"); return; }	//printf("env: %02x %02x %02x\n", buf[0], buf[1], buf[2]); //printf("ret: %02x %02x %02x %02x\n", buf2[0], buf2[1], buf2[2], buf2[3]);

com_serial=1; failcount=0; return buf2; }

////////// // Write n bytes int the 2 bytes address add1 add2 ////////// void spi_write(int add1,int add2,int nbytes,char value[10],int file) {	unsigned char	buf[32], buf2[32]; int status;

memset(buf, 0, sizeof buf); memset(buf2, 0, sizeof buf2); buf[0] = 0x00; buf[1] = add1; buf[2] = add2; if (nbytes>=1) buf[3] = value[0]; if (nbytes>=2) buf[4] = value[1]; if (nbytes>=3) buf[5] = value[2]; if (nbytes>=4) buf[6] = value[3]; xfer[0].tx_buf = (unsigned long)buf; xfer[0].len = nbytes+3; /* Length of command to write*/ status = ioctl(file, SPI_IOC_MESSAGE(1), xfer); if (status < 0) {		perror("SPI_IOC_MESSAGE"); return; }	//printf("env: %02x %02x %02x\n", buf[0], buf[1], buf[2]); //printf("ret: %02x %02x %02x %02x\n", buf2[0], buf2[1], buf2[2], buf2[3]);

com_serial=1; failcount=0; }

Usage example:

<pre class="brush: ini"> char *buffer; char buf[10];

file=spi_init("/dev/spidev0.0"); //dev

buf[0] = 0x41; buf[1] = 0xFF; spi_write(0xE6,0x0E,2,buf,file); //this will write value 0x41FF to the address 0xE60E

buffer=(char *)spi_read(0xE6,0x0E,4,file); //reading the address 0xE60E

close(file);

For info it is possible to use all the 12000000 Hz frequency limit transfers.

=SPI NOR Flash= The Allwinner Boot Rom can boot from NOR flash packaged over an SPI interface. There are currently no known devices that have onboard NOR flash.