Re: [PATCH 6/6] tty: serial: Add 8250-core based omap driver
From: Tony Lindgren
Date: Fri Jul 11 2014 - 02:41:58 EST
* Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> [140710 08:50]:
> On 07/10/2014 09:09 AM, Tony Lindgren wrote:
> > You can test this pretty easily on beagleboard xm for example
> > using v3.16-r4:
> I tried this with am335x-evm, dra7-evm and beaglebone (omap5-uevm and
> am335x-evmsk didn't want to boot a kernel and omap4-blaze didn't even
> want to show MLO/U-boot) with the same result.
None of these SoCs support off-idle with mainline kernel so testing
with those is not enough :) Best to use some omap3 based device for
So far I have verified that beagleboard xm, n900, and omap3730-evm
all hit off-idle with v3.16-rc4.
> > 1. Compile the kernel using omap2plus_defconfig and enable your
> > driver. USB EHCI needs to be disabled and OTG port should
> > not have a USB cable connected.
> EHCI was already disabled in the config. OTG was not connected.
> > 2. Boot with init=/bin/sh to keep user space timers to minimum
> > at least until you have verified to hit off-idle
> I had network up and configured. Was that okay? I also tried
> "ifconfig eth0 down; sleep 10; ifconfig eth0 up" to see if it works.
That's fine for GPMC connected devices, devices with Ethernet on
EHCI won't idle properly AFAIK.
> > 3. Enable UART timeouts with something like this. You may need
> > to update it for ttyS, I just changed ttyO to ttyS here:
> > #!/bin/bash
> > uarts=$(find /sys/class/tty/ttyS*/device/power/ -type d)
> > for uart in $uarts; do
> > echo 3000 > $uart/autosuspend_delay_ms
> > done
> > uarts=$(find /sys/class/tty/ttyS*/power/ -type d)
> > for uart in $uarts; do
> > echo enabled > $uart/wakeup
> > echo auto > $uart/control
> > done
> > echo 1 > /sys/kernel/debug/pm_debug/enable_off_mode
> > 4. Wait for UART to time out and verify you hit off-idle by
> > looking at the debugfs entry:
> > # cat /sys/kernel/debug/pm_debug/count
> > ...
> > core_pwrdm (ON),OFF:6,RET:0,INA:0,ON:7,RET-LOGIC-OFF:0,RET-MEMBANK1-OFF:0,RET-MEMBANK2-OFF:0
> That core_pwrdm shows only up on dra7. However with both drivers (mine
> and the current omap serial) the UART went down after three secs (as
> expected) and didn't accept any characters while writing on the
> console. If I wrote something on it via network (like echo a >
> /dev/ttyO0) it came back and was working as long as I kept it busy. The
> thing is that RX does not wake it up. Any idea?
If the RX pin does not wake it up, you need to configure the
pinctrl-single entry for it, and configure that pin as a wake-up
interrupt. See the interrupts-extended entry in omap3-beagle-xm.dts.
> Also, while it was I checked the core_pwrdm and I had ON:1 and OFF:0.
> So something is not right.
> Since Dra7 has some things missing I tried it on am335x with the same
> behavior. Should it work here?
Yes only omap3 currently has the pieces needed for off-idle in the
> > I just tried testing this, but did not get far on my omap3 evm:
> > [ 5.445953] Unhandled fault: external abort on non-linefetch (0x1028) at 0xfb020000
> > [ 5.453674] Internal error: : 1028 [#1] SMP ARM
> > [ 5.458221] Modules linked in:
> > [ 5.461334] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.16.0-rc4-00006-gaab2c6a #98
> > [ 5.469024] task: ce058b00 ti: ce05a000 task.ti: ce05a000
> > [ 5.474456] PC is at mem32_serial_in+0xc/0x1c
> > [ 5.478851] LR is at serial8250_do_startup+0xc8/0x89c
> > [ 5.483917] pc : [<c0346f90>] lr : [<c034ab2c>] psr: 60000113
> > [ 5.483917] sp : ce05bd10 ip : c0a0aba8 fp : ce275400
> > [ 5.495452] r10: 00000000 r9 : cda7a680 r8 : ce27568c
> > [ 5.500701] r7 : ce275400 r6 : 00000000 r5 : ce280408 r4 : c10b6234
> > [ 5.507263] r3 : fb020000 r2 : 00000002 r1 : fb020000 r0 : c10b6234
> > [ 5.513854] Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment kernel
> > [ 5.521179] Control: 10c5387d Table: 80004019 DAC: 00000015
> > [ 5.526977] Process swapper/0 (pid: 1, stack limit = 0xce05a248)
> > [ 5.532989] Stack: (0xce05bd10 to 0xce05c000)
> > ...
> > [ 5.734771] [<c0346f90>] (mem32_serial_in) from [<c034ab2c>] (serial8250_do_startup+0xc8/0x89c)
> > [ 5.743530] [<c034ab2c>] (serial8250_do_startup) from [<c03461f8>] (uart_startup.part.3+0x7c/0x1dc)
> > [ 5.752624] [<c03461f8>] (uart_startup.part.3) from [<c0346d68>] (uart_open+0xe4/0x124)
> > [ 5.760681] [<c0346d68>] (uart_open) from [<c032c19c>] (tty_open+0x130/0x58c)
> > [ 5.767852] [<c032c19c>] (tty_open) from [<c01216f4>] (chrdev_open+0x9c/0x174)
> > [ 5.775115] [<c01216f4>] (chrdev_open) from [<c011b8d4>] (do_dentry_open+0x1d0/0x310)
> > [ 5.783020] [<c011b8d4>] (do_dentry_open) from [<c011bd98>] (finish_open+0x34/0x4c)
> > [ 5.790710] [<c011bd98>] (finish_open) from [<c012a8f8>] (do_last.isra.27+0x5a4/0xb98)
> > [ 5.798675] [<c012a8f8>] (do_last.isra.27) from [<c012afa0>] (path_openat+0xb4/0x5e4)
> > [ 5.806549] [<c012afa0>] (path_openat) from [<c012b7dc>] (do_filp_open+0x2c/0x80)
> > [ 5.814086] [<c012b7dc>] (do_filp_open) from [<c011cd14>] (do_sys_open+0x100/0x1d0)
> > [ 5.821777] [<c011cd14>] (do_sys_open) from [<c07b7ce0>] (kernel_init_freeable+0x124/0x1c8)
> > [ 5.830200] [<c07b7ce0>] (kernel_init_freeable) from [<c054eb90>] (kernel_init+0x8/0xe4)
> > [ 5.838348] [<c054eb90>] (kernel_init) from [<c000e868>] (ret_from_fork+0x14/0x2c)
> > Sounds like the clocks are not enabled properly?
> puh. So after staring a while at your backtrace I realized that
> shutdown & startup callbacks are not overwritten properly. Well, thanks
> for that. Anyway, even serial8250_do_startup() has
> pm_runtime_get_sync() before first register access so I have no idea
> where this is coming from.
Maybe because the console is enabled for that port?
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/