Re: [microblaze-uclinux] Low level access

[Rod Campbell <rod@xxxxxxxxxxxxxxxxxx>]

We do direct access to FPGA IP using the following macros:

#include <stdint.h>           // integer data types

// access 32-bit register data.
#define LAII_REG_READ(reg) (*(volatile uint32_t *)(reg))
#define LAII_REG_WRITE(reg,val)     { (*(volatile uint32_t *)(reg) = val); }

Our interface between a uClinux app and the FPGA IP is via these 32-bit 
memory-mapped "registers".
It is true that doing this leaves you open to problems if the value of 
reg is not right.

Rod Campbell

Benny Chen wrote:
> Hi Duy-ky,
> Without hardware MMU support it is even more important for your 
> application code to access your ipcore via the IOCTL() command.  This 
> is so because it would help prevent your application code from 
> bringing down the kernel when it does incorrect memory access due to 
> pointer referencing error.
>
> The recommended way is to write a thin driver for your ipcore and 
> provide access to the application program via the device file interface.
>
> If you like the idea of referencing memory via their address instead 
> of IOCTL then look at mmap() support for your driver.
>
> Cheers,
> B,
>
> Duy-Ky Nguyen wrote:
> > Hello,
> >
> > I got some experiences on low level access in Linux using X86 and 
> > MPC8272. They were "real Linux" with memory protection between kernel 
> > and user space, so I had to go through ioctl for low level access.
> >
> > I'm quite aware that uCLinux does not have that kind of protection. 
> > In experience, loose something goes together with gain some thing, so 
> > I expect I'm able to have more direct access of low level.
> >
> > Let's say I have a user_ip at 0x40080000, I've created a new myapp_hw 
> > in user-apps, and failed to compile a code using
> >
> > // Start of code
> > #include <asm/io.h>
> > #define BASEADDR 0x40080000
> > . .
> > x = inl((volatile unsigned *) (BASEADDR));    // read-only reg
> > outl(1, (volatile unsigned *) (BASEADDR));    // write 1 to RWreg
> > ..
> > // End of code
> >
> > I had very long list of error from the compilation.
> >
> > I'd really appreciate if I'd be shown how to use these low-level IO 
> > access functions.
> >
> > Thanks a lot,
> >
> > Duy-Ky
> >
> >
> >
> >
> >
> > ___________________________
> > microblaze-uclinux mailing list
> > microblaze-uclinux@xxxxxxxxxxxxxx
> > Project Home Page : http://www.itee.uq.edu.au/~jwilliams/mblaze-uclinux
> > Mailing List Archive : 
> > http://www.itee.uq.edu.au/~listarch/microblaze-uclinux/
> ___________________________
> microblaze-uclinux mailing list
> microblaze-uclinux@xxxxxxxxxxxxxx
> Project Home Page : http://www.itee.uq.edu.au/~jwilliams/mblaze-uclinux
> Mailing List Archive : 
> http://www.itee.uq.edu.au/~listarch/microblaze-uclinux/

___________________________
microblaze-uclinux mailing list
microblaze-uclinux@xxxxxxxxxxxxxx
Project Home Page : http://www.itee.uq.edu.au/~jwilliams/mblaze-uclinux
Mailing List Archive : http://www.itee.uq.edu.au/~listarch/microblaze-uclinux/