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Hi
I am struggling with reading and writing to mcsp registers and I would be grateful if anyone can share an example.
I need to modify and read mcspi2 registers for my GPIO driver and have tried phys_to_virt macro which returns an address which is not same as the virtual address when mcspi2 master is registered.
If I had code the virtual address of mcspi2 at the time of registration and read the registers it returns all 0's
The debug statement shows this
[ 0.038635] omap2_mcspi omap2_mcspi.1: r->start 48098000 r->end 480980ff mcspi->base cd89936c
[ 0.043792] omap2_mcspi omap2_mcspi.1: registered master spi1
[ 0.051788] omap2_mcspi omap2_mcspi.2: r->start 4809a000 r->end 4809a0ff mcspi->base cd89916c
[ 0.056884] omap2_mcspi omap2_mcspi.2: registered master spi2
[ 0.063171] spi spi2.0: setup: speed 1500000, sample leading edge, clk normal
[ 0.068634] spi spi2.0: setup mode 0, 8 bits/w, 1500000 Hz max --> 0
[ 0.073791] omap2_mcspi omap2_mcspi.2: registered child spi2.0
[ 0.080169] spi spi2.1: setup: speed 12000000, sample leading edge, clk normal
[ 0.085693] spi spi2.1: setup mode 0, 8 bits/w, 12000000 Hz max --> 0
[ 0.090820] omap2_mcspi omap2_mcspi.2: registered child spi2.1
[ 0.098785] omap2_mcspi omap2_mcspi.3: r->start 480b8000 r->end 480b80ff mcspi->base cd8afb6c
[ 0.103851] omap2_mcspi omap2_mcspi.3: registered master spi3
[ 0.111816] omap2_mcspi omap2_mcspi.4: r->start 480ba000 r->end 480ba0ff mcspi->base cd8af96c
[ 0.116882] omap2_mcspi omap2_mcspi.4: registered master spi4
this is what i get when i use
*************************************
struct xra1405
{
struct spi_device *spi;
struct device *dev;
struct xra1405_platform_data *pdata;
struct spi_message *msg[5];
struct spi_transfer *xfer[18];
struct mutex lock;
int cs_change;
void __iomem *base;
unsigned long phys;
};
*************************************
struct xra1405 *ts;
ts->base = phys_to_virt(0x4809A000);
On reading registers I get
[ 6.230163] xra1405 spi2.1: xra1405->base cdabb938
[ 6.238128] READ REGISTER OMAP2_MCSPI_REVISION fa09a000
[ 6.246704] READ REGISTER OMAP2_MCSPI_SYSCONFIG 00000000
[ 6.255371] READ REGISTER OMAP2_MCSPI_SYSSTATUS 00000000
[ 6.264038] READ REGISTER OMAP2_MCSPI_IRQSTATUS 00000000
[ 6.272705] READ REGISTER OMAP2_MCSPI_IRQENABLE 00000000
[ 6.281555] READ REGISTER OMAP2_MCSPI_WAKEUPENABLE 00000000
[ 6.290161] READ REGISTER OMAP2_MCSPI_SYST 00000000
[ 6.298370] READ REGISTER OMAP2_MCSPI_MODULCTRL 00000000
Can someone share an exaple of how to access mcspi->base value from specific driver say forexaple GPIO, Touchscreen etc.
Any help would be great.
Thanks
Hi Ali,
Try the sample kernel module driver to read the SPI2 register.
I hope that you know how to build kernel module driver with this code.
1) Create Makefile and put entry for the kernel code
obj-m += sample.c
2) Build
To build
make -C <kernel source dir> -M=`pwd` modules
To clean
make -C <kernel source dir> -M=`pwd` clean
3) You would get "sample.ko" after successful build
Note that you may get the error from include section since I have used this code for the latest kernel code so change the include files appropriately.
/*
* Sample driver
*
* This file is subject to the terms and conditions of the GNU General Public
* License.
*
* AUTHOR : Titusrathinaraj Stalin
* EMAIL : x0213399@ti.com
*
*/
/* Include linux kernel header files */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <asm/uaccess.h>
#include <linux/device.h>
#include <asm/gpio.h>
#include <linux/interrupt.h>
#include <asm/irq.h>
#include <linux/sched.h>
#include <linux/irq.h>
#include <linux/delay.h>
#include<linux/proc_fs.h> // Required for proc entry creation
#include <linux/mm.h>
#include <linux/io.h>
#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <asm/uaccess.h>
#include <linux/device.h>
#include <asm/gpio.h>
#include <linux/interrupt.h>
#include <asm/irq.h>
#include <linux/sched.h>
#include <linux/irq.h>
#include <linux/delay.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Titus S");
MODULE_DESCRIPTION("Sample driver");
#define SPI2_BASE_ADDR 0x4809A000
#define SPI_MODULECTRL_OFFSET 0x28
int sample_init(void)
{
unsigned int *SPI2_MODULECTRL = SPI2_MODULECTRL = ioremap(SPI2_BASE_ADDR+SPI2_MODULECTRL_OFFSET,4); //SPI2_MODULECTRL_OFFSET
printk(KERN_ALERT "sample driver is inserted sucessfully SPI2_MODULECTRL register %p\n",*SPI2_MODULECTRL);
return 0;
}
void sample_exit(void)
{
printk(KERN_ALERT "sample driver is ejected sucessfully...\n");
}
/* Register driver to the kernel */
module_init(sample_init);
module_exit(sample_exit);
make -C <kernel source dir> -M=`pwd` modules
