Intel's XScale Microarchitecture 80312 companion processor provides a 
Performance Monitoring Unit (PMON) that can be utilized to provide 
information that can be useful for fine tuning of code.  This text 
file describes the API that's been developed for use by Linux kernel 
programmers.  Note that to get the most usage out of the PMON, 
I highly reccomend getting the XScale reference manual from Intel[1] 
and looking at chapter 12.
 
To use the PMON, you must #include <asm-arm/arch-iop310/pmon.h> in your 
source file.
 
Since there's only one PMON, only one user can currently use the PMON
at a given time.  To claim the PMON for usage, call iop310_pmon_claim() which
returns an identifier.  When you are done using the PMON, call 
iop310_pmon_release() with the id you were given earlier.
 
The PMON consists of 14 registers that can be used for performance measurements.  
By combining different statistics, you can derive complex performance metrics.
 
To start the PMON, just call iop310_pmon_start(mode).  Mode tells the PMON what 
statistics to capture and can each be one of:

    IOP310_PMU_MODE0
    Performance Monitoring Disabled	

    IOP310_PMU_MODE1
    Primary PCI bus and internal agents (bridge, dma Ch0, dam Ch1, patu)

    IOP310_PMU_MODE2
    Secondary PCI bus and internal agents (bridge, dma Ch0, dam Ch1, patu)

    IOP310_PMU_MODE3
    Secondary PCI bus and internal agents (external masters 0..2 and Intel
    80312 I/O companion chip)

    IOP310_PMU_MODE4
    Secondary PCI bus and internal agents (external masters 3..5 and Intel
    80312 I/O companion chip)

    IOP310_PMU_MODE5
    Intel 80312 I/O companion chip internal bus, DMA Channels and Application
    Accelerator

    IOP310_PMU_MODE6
    Intel 80312 I/O companion chip internal bus, PATU, SATU and Intel 80200
    processor

    IOP310_PMU_MODE7
    Intel 80312 I/O companion chip internal bus, Primary PCI bus, Secondary
    PCI bus and Secondary PCI agents (external masters 0..5 & Intel 80312 I/O
    companion chip)

To get the results back, call iop310_pmon_stop(&results) where results is 
defined as follows:

typedef struct _iop310_pmon_result
{
	u32 timestamp;			/* Global Time Stamp Register */
	u32 timestamp_overflow;		/* Time Stamp overflow count */
	u32 event_count[14];		/* Programmable Event Counter 
					   Registers 1-14 */
	u32 event_overflow[14];		/* Overflow counter for PECR1-14 */
} iop310_pmon_res_t;


--
This code is still under development, so please feel free to send patches,
questions, comments, etc to me.

Deepak Saxena <dsaxena@mvista.com>