From 1a391e20c39026f4de0d137f9b2dc64f1f8462c0 Mon Sep 17 00:00:00 2001 From: Guenter Roeck Date: Tue, 22 Oct 2019 16:50:35 +0100 Subject: [PATCH] hw/timer/exynos4210_mct: Initialize ptimer before starting it MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit When booting a recent Linux kernel, the qemu message "Timer with delta zero, disabling" is seen, apparently because a ptimer is started before being initialized. Fix the problem by initializing the offending ptimer before starting it. The bug is effectively harmless in the old QEMUBH setup because the sequence of events is: * the delta zero means the timer expires immediately * ptimer_reload() arranges for exynos4210_gfrc_event() to be called * ptimer_reload() notices the zero delta and disables the timer * later, the QEMUBH runs, and exynos4210_gfrc_event() correctly configures the timer and restarts it In the new transaction based API the bug is still harmless, but differences of when the callback function runs mean the message is not printed any more: * ptimer_run() does nothing as it's inside a transaction block * ptimer_transaction_commit() sees it has work to do and calls ptimer_reload() * the zero delta means the timer expires immediately * ptimer_reload() calls exynos4210_gfrc_event() directly * exynos4210_gfrc_event() configures the timer * the delta is no longer zero so ptimer_reload() doesn't complain (the zero-delta test is after the trigger-callback in the ptimer_reload() function) Regardless, the behaviour here was not intentional, and we should just program the ptimer correctly to start with. Signed-off-by: Guenter Roeck Reviewed-by: Philippe Mathieu-Daudé Tested-by: Philippe Mathieu-Daudé Signed-off-by: Peter Maydell Message-id: 20191018143149.9216-1-peter.maydell@linaro.org [PMM: Expansion/clarification of the commit message: the message is about a zero delta, not a zero period; added detail to the commit message of the analysis of what is happening and why the kernel boots even with the message; added note that the message goes away with the new ptimer API] Signed-off-by: Peter Maydell --- hw/timer/exynos4210_mct.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/hw/timer/exynos4210_mct.c b/hw/timer/exynos4210_mct.c index 7225758414..944120aea5 100644 --- a/hw/timer/exynos4210_mct.c +++ b/hw/timer/exynos4210_mct.c @@ -1254,7 +1254,7 @@ static void exynos4210_mct_write(void *opaque, hwaddr offset, /* Start FRC if transition from disabled to enabled */ if ((value & G_TCON_TIMER_ENABLE) > (old_val & G_TCON_TIMER_ENABLE)) { - exynos4210_gfrc_start(&s->g_timer); + exynos4210_gfrc_restart(s); } if ((value & G_TCON_TIMER_ENABLE) < (old_val & G_TCON_TIMER_ENABLE)) {