Forum Post: How to access uncached mscpi- base address from GPIO Driver

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