From 8d71beaf1e6b49266c4d98286f4ce6c874c998ae Mon Sep 17 00:00:00 2001 From: Axel Heider Date: Sun, 20 Nov 2022 20:05:25 +0100 Subject: [PATCH] hw/timer/imx_epit: fix compare timer handling - fix #1263 for CR writes - rework compare time handling - The compare timer has to run even if CR.OCIEN is not set, as SR.OCIF must be updated. - The compare timer fires exactly once when the compare value is less than the current value, but the reload values is less than the compare value. - The compare timer will never fire if the reload value is less than the compare value. Disable it in this case. Signed-off-by: Axel Heider [PMM: fixed minor style nits] Reviewed-by: Peter Maydell Signed-off-by: Peter Maydell --- hw/timer/imx_epit.c | 192 ++++++++++++++++++++++++++------------------ 1 file changed, 116 insertions(+), 76 deletions(-) diff --git a/hw/timer/imx_epit.c b/hw/timer/imx_epit.c index cf13496165..3a869782bc 100644 --- a/hw/timer/imx_epit.c +++ b/hw/timer/imx_epit.c @@ -6,6 +6,7 @@ * Originally written by Hans Jiang * Updated by Peter Chubb * Updated by Jean-Christophe Dubois + * Updated by Axel Heider * * This code is licensed under GPL version 2 or later. See * the COPYING file in the top-level directory. @@ -151,33 +152,126 @@ static uint64_t imx_epit_read(void *opaque, hwaddr offset, unsigned size) return reg_value; } -/* Must be called from ptimer_transaction_begin/commit block for s->timer_cmp */ -static void imx_epit_reload_compare_timer(IMXEPITState *s) +/* + * Must be called from a ptimer_transaction_begin/commit block for + * s->timer_cmp, but outside of a transaction block of s->timer_reload, + * so the proper counter value is read. + */ +static void imx_epit_update_compare_timer(IMXEPITState *s) { - if ((s->cr & (CR_EN | CR_OCIEN)) == (CR_EN | CR_OCIEN)) { - /* if the compare feature is on and timers are running */ - uint32_t tmp = ptimer_get_count(s->timer_reload); - uint64_t next; - if (tmp > s->cmp) { - /* It'll fire in this round of the timer */ - next = tmp - s->cmp; - } else { /* catch it next time around */ - next = tmp - s->cmp + ((s->cr & CR_RLD) ? EPIT_TIMER_MAX : s->lr); + uint64_t counter = 0; + bool is_oneshot = false; + /* + * The compare timer only has to run if the timer peripheral is active + * and there is an input clock, Otherwise it can be switched off. + */ + bool is_active = (s->cr & CR_EN) && imx_epit_get_freq(s); + if (is_active) { + /* + * Calculate next timeout for compare timer. Reading the reload + * counter returns proper results only if pending transactions + * on it are committed here. Otherwise stale values are be read. + */ + counter = ptimer_get_count(s->timer_reload); + uint64_t limit = ptimer_get_limit(s->timer_cmp); + /* + * The compare timer is a periodic timer if the limit is at least + * the compare value. Otherwise it may fire at most once in the + * current round. + */ + bool is_oneshot = (limit >= s->cmp); + if (counter >= s->cmp) { + /* The compare timer fires in the current round. */ + counter -= s->cmp; + } else if (!is_oneshot) { + /* + * The compare timer fires after a reload, as it is below the + * compare value already in this round. Note that the counter + * value calculated below can be above the 32-bit limit, which + * is legal here because the compare timer is an internal + * helper ptimer only. + */ + counter += limit - s->cmp; + } else { + /* + * The compare timer won't fire in this round, and the limit is + * set to a value below the compare value. This practically means + * it will never fire, so it can be switched off. + */ + is_active = false; } - ptimer_set_count(s->timer_cmp, next); } + + /* + * Set the compare timer and let it run, or stop it. This is agnostic + * of CR.OCIEN bit, as this bit affects interrupt generation only. The + * compare timer needs to run even if no interrupts are to be generated, + * because the SR.OCIF bit must be updated also. + * Note that the timer might already be stopped or be running with + * counter values. However, finding out when an update is needed and + * when not is not trivial. It's much easier applying the setting again, + * as this does not harm either and the overhead is negligible. + */ + if (is_active) { + ptimer_set_count(s->timer_cmp, counter); + ptimer_run(s->timer_cmp, is_oneshot ? 1 : 0); + } else { + ptimer_stop(s->timer_cmp); + } + } static void imx_epit_write_cr(IMXEPITState *s, uint32_t value) { - uint32_t freq = 0; uint32_t oldcr = s->cr; s->cr = value & 0x03ffffff; if (s->cr & CR_SWR) { - /* handle the reset */ + /* + * Reset clears CR.SWR again. It does not touch CR.EN, but the timers + * are still stopped because the input clock is disabled. + */ imx_epit_reset(s, false); + } else { + uint32_t freq; + uint32_t toggled_cr_bits = oldcr ^ s->cr; + /* re-initialize the limits if CR.RLD has changed */ + bool set_limit = toggled_cr_bits & CR_RLD; + /* set the counter if the timer got just enabled and CR.ENMOD is set */ + bool is_switched_on = (toggled_cr_bits & s->cr) & CR_EN; + bool set_counter = is_switched_on && (s->cr & CR_ENMOD); + + ptimer_transaction_begin(s->timer_cmp); + ptimer_transaction_begin(s->timer_reload); + freq = imx_epit_get_freq(s); + if (freq) { + ptimer_set_freq(s->timer_reload, freq); + ptimer_set_freq(s->timer_cmp, freq); + } + + if (set_limit || set_counter) { + uint64_t limit = (s->cr & CR_RLD) ? s->lr : EPIT_TIMER_MAX; + ptimer_set_limit(s->timer_reload, limit, set_counter ? 1 : 0); + if (set_limit) { + ptimer_set_limit(s->timer_cmp, limit, 0); + } + } + /* + * If there is an input clock and the peripheral is enabled, then + * ensure the wall clock timer is ticking. Otherwise stop the timers. + * The compare timer will be updated later. + */ + if (freq && (s->cr & CR_EN)) { + ptimer_run(s->timer_reload, 0); + } else { + ptimer_stop(s->timer_reload); + } + /* Commit changes to reload timer, so they can propagate. */ + ptimer_transaction_commit(s->timer_reload); + /* Update compare timer based on the committed reload timer value. */ + imx_epit_update_compare_timer(s); + ptimer_transaction_commit(s->timer_cmp); } /* @@ -186,60 +280,6 @@ static void imx_epit_write_cr(IMXEPITState *s, uint32_t value) * - write to CR.EN or CR.OCIE */ imx_epit_update_int(s); - - /* - * TODO: could we 'break' here for reset? following operations appear - * to duplicate the work imx_epit_reset() already did. - */ - - ptimer_transaction_begin(s->timer_cmp); - ptimer_transaction_begin(s->timer_reload); - - /* - * Update the frequency. In case of a reset the input clock was - * switched off, so this can be skipped. - */ - if (!(s->cr & CR_SWR)) { - freq = imx_epit_get_freq(s); - if (freq) { - ptimer_set_freq(s->timer_reload, freq); - ptimer_set_freq(s->timer_cmp, freq); - } - } - - if (freq && (s->cr & CR_EN) && !(oldcr & CR_EN)) { - if (s->cr & CR_ENMOD) { - if (s->cr & CR_RLD) { - ptimer_set_limit(s->timer_reload, s->lr, 1); - ptimer_set_limit(s->timer_cmp, s->lr, 1); - } else { - ptimer_set_limit(s->timer_reload, EPIT_TIMER_MAX, 1); - ptimer_set_limit(s->timer_cmp, EPIT_TIMER_MAX, 1); - } - } - - imx_epit_reload_compare_timer(s); - ptimer_run(s->timer_reload, 0); - if (s->cr & CR_OCIEN) { - ptimer_run(s->timer_cmp, 0); - } else { - ptimer_stop(s->timer_cmp); - } - } else if (!(s->cr & CR_EN)) { - /* stop both timers */ - ptimer_stop(s->timer_reload); - ptimer_stop(s->timer_cmp); - } else if (s->cr & CR_OCIEN) { - if (!(oldcr & CR_OCIEN)) { - imx_epit_reload_compare_timer(s); - ptimer_run(s->timer_cmp, 0); - } - } else { - ptimer_stop(s->timer_cmp); - } - - ptimer_transaction_commit(s->timer_cmp); - ptimer_transaction_commit(s->timer_reload); } static void imx_epit_write_sr(IMXEPITState *s, uint32_t value) @@ -266,14 +306,10 @@ static void imx_epit_write_lr(IMXEPITState *s, uint32_t value) /* If IOVW bit is set then set the timer value */ ptimer_set_count(s->timer_reload, s->lr); } - /* - * Commit the change to s->timer_reload, so it can propagate. Otherwise - * the timer interrupt may not fire properly. The commit must happen - * before calling imx_epit_reload_compare_timer(), which reads - * s->timer_reload internally again. - */ + /* Commit the changes to s->timer_reload, so they can propagate. */ ptimer_transaction_commit(s->timer_reload); - imx_epit_reload_compare_timer(s); + /* Update the compare timer based on the committed reload timer value. */ + imx_epit_update_compare_timer(s); ptimer_transaction_commit(s->timer_cmp); } @@ -281,8 +317,9 @@ static void imx_epit_write_cmp(IMXEPITState *s, uint32_t value) { s->cmp = value; + /* Update the compare timer based on the committed reload timer value. */ ptimer_transaction_begin(s->timer_cmp); - imx_epit_reload_compare_timer(s); + imx_epit_update_compare_timer(s); ptimer_transaction_commit(s->timer_cmp); } @@ -322,6 +359,9 @@ static void imx_epit_cmp(void *opaque) { IMXEPITState *s = IMX_EPIT(opaque); + /* The cmp ptimer can't be running when the peripheral is disabled */ + assert(s->cr & CR_EN); + DPRINTF("sr was %d\n", s->sr); /* Set interrupt status bit SR.OCIF and update the interrupt state */ s->sr |= SR_OCIF;