Hi Marcel, [also added Lucas] On 2015-12-30 19:12, Marcel Ziswiler wrote: > Continuing on the Apalis iMX6 mainlining work started by Petr Štetiar I > noticed that it only boots when rebooting from NXP's downstream 3.14.28 > kernel or mainline otherwise (e.g. when cold booted) I did not get any > serial debug output at all. Enabling earlyprintk I got the following: > > [ 1.136806] INFO: trying to register non-static key. > [ 1.136871] 2020000.serial: ttymxc0 at MMIO 0x2020000 (irq = 25, > base_baud = 5000000) is a IMX > [ 1.150651] the code is fine but needs lockdep annotation. > [ 1.150653] turning off the locking correctness validator. > [ 1.150664] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.4.0-rc6- > next-20151223-00002-g6008f30-dirty #27 > [ 1.150668] Hardware name: Freescale i.MX6 Quad/DualLite (Device > Tree) > [ 1.150675] Backtrace: > [ 1.150701] [<c010c45c>] (dump_backtrace) from [<c010c654>] > (show_stack+0x18/0x1c) > [ 1.150722] r7:00000000 r6:c0d20848 r5:00000000 r4:00000000 > [ 1.150739] [<c010c63c>] (show_stack) from [<c03dadcc>] > (dump_stack+0x8c/0xa4) > [ 1.150760] [<c03dad40>] (dump_stack) from [<c016b60c>] > (__lock_acquire+0x1d88/0x1eb4) > [ 1.150774] r7:00000000 r6:c0d063f8 r5:c155f834 r4:e503bc20 > [ 1.150785] [<c0169884>] (__lock_acquire) from [<c016bf54>] > (lock_acquire+0x74/0x94) > [ 1.150803] r10:c0d6eb5e r9:e597b300 r8:00000019 r7:00000001 > r6:00000001 r5:60000193 > [ 1.150808] r4:00000000 > [ 1.150821] [<c016bee0>] (lock_acquire) from [<c08d49d4>] > (_raw_spin_lock_irqsave+0x40/0x54) > [ 1.150834] r7:000052c8 r6:c0481470 r5:40000193 r4:e503bc10 > [ 1.150852] [<c08d4994>] (_raw_spin_lock_irqsave) from [<c0481470>] > (imx_rxint+0x20/0x2a4) > [ 1.150862] r6:00000000 r5:000052d0 r4:e503bc10 > [ 1.150874] [<c0481450>] (imx_rxint) from [<c0482540>] > (imx_int+0x170/0x1f4) > > Debugging a little further I noticed this actually happening after > calling devm_request_irq() during serial_imx_probe() even before > uart_add_one_port() did initialise the spin_lock acquired in > imx_rxint(). Turns out the data carrier detect interrupt fired > immediately upon requesting interrupts. This patch fixes this by > explicitly disabling data carrier detect before requesting interrupts. I actually hit a very similar issue on the Colibri iMX6 and hence looked into this too. In our downstream tree, I fixed it in imx_startup, which is probably the wrong place actually... > > Signed-off-by: Marcel Ziswiler <marcel.ziswiler@xxxxxxxxxxx> > > --- > > drivers/tty/serial/imx.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c > index 9362f54c..b1588f9 100644 > --- a/drivers/tty/serial/imx.c > +++ b/drivers/tty/serial/imx.c > @@ -2032,6 +2032,11 @@ static int serial_imx_probe(struct platform_device *pdev) > UCR1_TXMPTYEN | UCR1_RTSDEN); > writel_relaxed(reg, sport->port.membase + UCR1); > > + /* Disable data carrier detect before requesting interrupts */ > + reg = readl_relaxed(sport->port.membase + UCR3); > + reg &= ~(UCR3_DCD); > + writel_relaxed(reg, sport->port.membase + UCR3); > + Note that UCR3_DCD has a different meaning in DCE mode. As a DCE, the bit should be kept 1 (we assume that the carrier is detected by default...) The dte_mode bit should be initialized at that point, hence just making that code conditional should account for that. What I also noticed is that the RI signal suffers the very same issue. We do not use the signal on our Colibri board, but we should disable that interrupt too. -- Stefan > clk_disable_unprepare(sport->clk_ipg); > > /* -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
