From mboxrd@z Thu Jan 1 00:00:00 1970 From: tony@atomide.com (Tony Lindgren) Date: Tue, 12 Apr 2016 11:42:50 -0700 Subject: [PATCH] ARM: omap2: am437x: rollback to use omap3_gptimer_timer_init() In-Reply-To: <570D3EC8.7090807@ti.com> References: <1460457775-23850-1-git-send-email-grygorii.strashko@ti.com> <20160412160448.GN5995@atomide.com> <570D3EC8.7090807@ti.com> Message-ID: <20160412184250.GT5995@atomide.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org * Grygorii Strashko [160412 11:31]: > On 04/12/2016 07:04 PM, Tony Lindgren wrote: > > * Grygorii Strashko [160412 03:44]: > >> The commit 55ee7017ee31 ("arm: omap2: board-generic: use > >> omap4_local_timer_init for AM437x") unintentionally changes the > >> clocksource devices for AM437x from OMAP GP Timer to SyncTimer32K. > >> > >> Unfortunately, the SyncTimer32K is starving from frequency deviation > >> as mentioned in commit 5b5c01359152 ("ARM: OMAP2+: AM43x: Use gptimer > >> as clocksource") and, as reported by Franklin [1], even its monotonic > >> nature is under question (most probably there is a HW issue, but it's > >> still under investigation). > >> > >> Taking into account above facts It's reasonable to rollback to the use > >> of omap3_gptimer_timer_init(). > > > > I thought only the ePOS EVM does not have the 32k clock available? > > Maybe this is the the old sync timer autocorrection drift issue? > > > > May be, as i mentioned in [1] it could be errata same as for Watchdog > Advisory 22 (or OMAP_TIMER_ERRATA_I103_I767). > > But as per commit 5b5c01359152 ("ARM: OMAP2+: AM43x: Use gptimer > as clocksource") there is no reason to use SyncTimer32K as > clocksource any way (not only on epos): > > commit 5b5c01359152f3ddaa1aa0e5d1141bc2b29ba2c5 > Author: Rajendra Nayak > Date: Fri Feb 7 15:51:26 2014 +0530 > > ARM: OMAP2+: AM43x: Use gptimer as clocksource > > The SyncTimer in AM43x is clocked using the following two sources: > 1) An inaccuarte 32k clock (CLK_32KHZ) derived from PER DPLL, causing system > time to go slowly (~10% deviation). > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > 2) external 32KHz RTC clock, which may not always be available on board like > in the case of ePOS EVM This sounds similar to recent "ARM: dts: dra7: Correct clock tree for sys_32k_ck", can you see if similar changes help for am43x? Regards, Tony