Here is a better patch for the touchpanel bug. It gives me a much better
compromise between stylus move accuracy and interrupt overhead.

Index: j720ssp.c
===================================================================
RCS file: /cvsroot/syssrc/sys/arch/hpcarm/dev/j720ssp.c,v
retrieving revision 1.8
diff -U4 -r1.8 j720ssp.c
--- j720ssp.c   2002/07/22 20:55:48     1.8
+++ j720ssp.c   2002/09/09 05:42:06
@@ -114,8 +114,9 @@
        struct tpcalib_softc sc_tpcalib;
 
        void *sc_kbdsi;
        void *sc_tpsi;
+       u_int64_t sc_tpdelay;
        struct callout sc_tptimeout;
        int sc_enabled;
 };
 
@@ -281,8 +282,9 @@
        callout_init(&sc->sc_tptimeout);
 
        /* Setup touchpad interrupt */
        sc->sc_tpsi = softintr_establish(IPL_SOFTCLOCK, j720tpsoft, sc);
+       sc->sc_tpdelay = 0;
        sa11x0_intr_establish(0, 9, 1, IPL_BIO, j720tp_intr, sc);
 
        /* LCD control is on the same bus */
        config_hook(CONFIG_HOOK_SET, CONFIG_HOOK_BRIGHTNESS,
@@ -378,12 +380,21 @@
 int
 j720tp_intr(void *arg)
 {
        struct j720ssp_softc *sc = arg;
+       int s;
+       u_int64_t now;
 
        bus_space_write_4(sc->sc_iot, sc->sc_gpioh, SAGPIO_EDR, 1 << 9);
 
-       softintr_schedule(sc->sc_tpsi);
+       s = splclock(); 
+       now = softclock_ticks;
+       splx(s);
+
+       if (now >= sc->sc_tpdelay) {
+               sc->sc_tpdelay = now + (hz / 12);
+               softintr_schedule(sc->sc_tpsi);
+       }       
 
        return (1);
 }
 


-- 
Emmanuel Dreyfus
manu@netbsd.org