On Mon, 2004-02-23 at 00:35, Dirk Roloff wrote:
> Hi List,
>
> I ve got the following problem:
>
> I have to write a driver for linux for a receiver-board.
> On this board is an AMCC S5933 pci-controler. Ok on this chip is a fifo (256
> bit).
> it has 2 regsiters MWAR (adress for DMA) and MWTC ( byte count for DMA)
> i will set both to a buffer - the count will be decemented and if it reaches
> zero i will get an interrupt (IRQ 5). in the drivers handler function i will
> just set MWAR to the next buffer and MWTC to the size of the buffer.
> So the board can start new DMA.
>
> Thats the background now the problem:
> the fifo, again its 256 bit will be filled by a satalite link with 1Mbit
> 1024000 bits per second. So i have a maximum of 0.25 milliseconds.
> and i have no idea how long it takes to get the pci for the next dma.
> But it woks most time, but ca. 10 times in an hour my pc is too slow.
> ( i think - i am not sure )
> So i loose some data. Its a receive only application so i have no handshake
> back in the air.
>
> if you google for interrupt latency - you will find "Linux is no RTOS" - so i
> find rtai and the adeos-patches. Great that sounds like it could work.
> untar kernel - patch - compile - crash - compile - read ... read ...
> understand ... ahhhh .... ok i changed the driver.
>
> Create a domain with prio 200
> adeos_virtualize_irq( IRQ 5 )
> compile - test .... the same problem .... i lose data ....
>
> My next try to understand whats going on .... create a new module to simulate
> what i think is going on.
> i put some soure at the end of this mail.
>
> I registered a linux handler vor irq 4 (serial device)
> this is just looping in a long loop doing nothing but using cpu power.
> ( a cat on ttyS0 will trigger one irq )
>
> i register a handler for all (0-15) irqs on the realtimeside.
> while the linux handler is running i am counting the irqs that will be
> entered
> in there.
>
> at the end of the linux_handler i printk what is captured by the realtime:
> IRQ 0 ( timer i think ) 300 times and more ...
>
> and then i see only one other IRQ happening once !!
> IRQ 9 ( scsii ) or IRQ 1 (keyboard) or IRQ 12 (mouse)
>
> realy - when i trigger IRQ 4 ( by cat /dev/ttyS0 ) the pc is hanging for
> about
> a sekond. i am spinning around the mouse and pressing the keyboard.
> i will only catch one IRQ.
>
> At the end of the linux handler i read out the pic. the catched irq for
> example 12 is marked out. And i couldn't find why. If i understand the code.
> an incomming IRQ will be acked and put in the ipipe. So new IRQs can happen.
> While walking down the ipipe.
>
> Back to my real problem - if there is a driver on the linux side - the ide or
> whatever using long time ( simulated by IRQ 4 ) i will not get in the
> realtime handler for my receiver card.
>
> My goal is: if IRQ 5 is raised - stop doing what ever you are doing - serve
> the board, and after that you have all time you need.
>
> i am working a week on my own, its sunday night and the weekend is also gone.
> i real need someone to help me.
>
> thanks
>
> Dirk
>
> ah ... here is now the code pices ( I cut out some stuff )
>
>
> init_module()
> - request_irq( 4 , linux_handler ) /* my simulation of a long running device
> handler here ist ttyS0 */
> - adeos_register_domain( myRealtime )
>
> in the DomainEntry()
> {
> int i;
> for(i=0;i<16;++i) adeos_virtualize_irq( i realtime_handler )
>
It would be interesting to know the flags passed to
adeos_virtualize_irq(). In any case, either the 4th arg should pass
IPIPE_PASS_MASK, or you realtime_handler() routine should call
adeos_propagate_irq(irq).
> for(;;) /* dont realy understand - copyed from rtai */
> adeos_suspend_domain();
> }
>
> static volatile int linux_irq = 0;
> static volatile int irq_count[256];
>
> static void linux_handler()
> {
> linux_irq = 1; /* we are running */
> /* just eating some cpu time - this will hang the linux for 1-2 sekonds */
> for(x=0;x<1000;++x)
> for(i=0;i<1000000;++i)
> if( x==0)++i;
> linux_irq = 0; /* we are finish */
> /* Ok lets have a look what happend in realtime */
> for( i=0;i<255;++i)
> {
> if( irq_count[i] != 0)
> printk ("linux_irq_handler: irq %d catched %d times\n",i ,irq_count[i]);
> }
> }
>
> static void
> realtime_handler ( unsigned int irq )
> {
> if(linux_irq != 0)
> {
> ++irq_count[irq]; /* add counter while linux_handler is running */
> }
> }
>
>
>
>
>
>
> _______________________________________________
> Adeos-main mailing list
> [email protected]
> http://mail.nongnu.org/mailman/listinfo/adeos-main
--
Philippe.
