From patchwork Mon Jul 4 15:24:25 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: mx25 gpt-clock issue, waits are too long Date: Mon, 04 Jul 2011 05:24:25 -0000 From: Torsten Mehnert X-Patchwork-Id: 103121 Message-Id: <3F263ABB4EDE344D974E1983B56807734FF6B38D@EX-DAG01.eckelmann.group> To: "linux-arm-kernel@lists.infradead.org" Hi, i am using barebox and standard linux (2.6.39.1) on my mx25 board. Under linux i now have the problem that a sleepwait or busywait results in a factor 1.8 too long waiting time. So sleep(10) results in ~18 seconds of waiting. I see through the clock registers and found that the clock source of the general purpose timer is set to UPLL(240MHz), divided by 2 its 120MHz. So when 120Mhz is factor 1.8 too much, then the correct value should be 66MHz. As this value can't be divided from UPLL i changed the clock source to AHB_DIV(133MHz), get the 66MHz and my sleep(10) are the proper 10 seconds. I think that the clock-mx25.c expected the CCM_MCR register to be cleared completely, which it's not in my case. I tested this issue again on the mx25-3stack evaluation board, with the same result. Old Kernel message: sched_clock: 32 bits at 120MHz, resolution 8ns, wraps every 35791ms New Kernel message: sched_clock: 32 bits at 66MHz, resolution 15ns, wraps every 64585ms This patch fixes this issue: Request for comment and feedback. From: T. Mehnert Date: Mon, 4 Jul 2011 15:53:30 +0200 Subject: [PATCH] GPT clock fix: corrected the clock source This patch changes the clock source for the general purpose timer of the arm/mx25 from UPLL to AHB_DIV. This fixes the problem, that sleep/busy wating waits factor 1.8 too long. Signed-off-by: Torsten Mehnert --- arch/arm/mach-imx/clock-imx25.c | 4 ++++ 1 files changed, 4 insertions(+), 0 deletions(-) -- 1.7.0.4 ECKELMANN AG Vorstand: Dr.-Ing. Gerd Eckelmann (Vorsitzender), Dr.-Ing. Peter Cordes, Dr.-Ing. Frank-Thomas Mellert Vorsitzender des Aufsichtsrats: Hubertus G. Krossa Sitz der Gesellschaft: Wiesbaden Amtsgericht Wiesbaden, HRB 12636 diff --git a/arch/arm/mach-imx/clock-imx25.c b/arch/arm/mach-imx/clock-imx25.c index a65838f..bf1ecda 100644 --- a/arch/arm/mach-imx/clock-imx25.c +++ b/arch/arm/mach-imx/clock-imx25.c @@ -328,6 +328,10 @@ int __init mx25_clocks_init(void) __raw_writel(__raw_readl(CRM_BASE+0x64) | (1 << 7) | (1 << 0), CRM_BASE + 0x64); + /* Clock source for gpt is ahb_div */ + __raw_writel(__raw_readl(CRM_BASE+0x64) & ~(1 << 5), + CRM_BASE + 0x64); + mxc_timer_init(&gpt_clk, MX25_IO_ADDRESS(MX25_GPT1_BASE_ADDR), 54); return 0;