Re: [PATCH V1] serial: imx: revert setup DCEDTE early and ensure DCD and RI irqs to be off
From: Uwe Kleine-König
Date: Tue May 23 2017 - 12:08:55 EST
Hello Steve,
On Tue, May 23, 2017 at 03:01:26PM +0000, Steve Twiss wrote:
> On 23 May 2017 15:37, Uwe Kleine-KÃnig wrote:
> > Subject: Re: [PATCH V1] serial: imx: revert setup DCEDTE early and ensure DCD and RI irqs to be off
> > On Tue, May 23, 2017 at 02:28:11PM +0000, Steve Twiss wrote:
> > > On 23 May 2017 15:10, Uwe Kleine-KÃnig wrote:
> > > > On Tue, May 23, 2017 at 01:17:26PM +0100, Steve Twiss wrote:
> > > > >
> > > > > Revert the commit e61c38d85b7392e ("serial: imx: setup DCEDTE early and
> > > > > ensure DCD and RI irqs to be off")
> > > > > The patch submitted to setup DCEDTE early and ensure DCD and RI irqs to
> > > > > be off, causes a serial console display problem the i.MX6Q SABRESD board.
> > > > > The console becomes unreadable and unwritable.
> > > > >
> > > > > Tested-by: Steve Twiss <stwiss.opensource@xxxxxxxxxxx>
> > > > > Signed-off-by: Steve Twiss <stwiss.opensource@xxxxxxxxxxx>
> > > >
> > > > You're not the first to report this issue but you still have the chance
> > > > to be the first to test a suggested patch for it.
> > >
> > > I've just applied your patch against a clean linux-next/v4.12-rc2
> > > I added your patch ...
> > >
> > > > http://marc.info/?l=linux-serial&m=149434029912947&w=2
> > >
> [...]
> > > I've added that to my working directory, but I am still seeing the corrupted
> > > console output on the i.MX6 Q (quad) board.
> >
> > I don't have a failing board (I think). So here are a few questions
> > about yours:
> >
> > - how does the dts snippet for your failing device look like?
>
> I am using the standard DTS from the v4.12-rc2 kernel, no changes.
> I did an earlier test yesterday using the DTS from v4.11 to see if it was the new
> imx7 changes that have recently gone into the kernel but I still see the same
> effect.
>
> > - This is not the device the console runs on, right?
>
> I am connected through the USB to UART, U22 on the i.MX6Q board.
> Terminal set to 115200 baud, no parity, 8bit data.
>
> > - Can you initialize the device in the bootloader and check if it is working there?
>
> I can get U-boot ok for all cases.
> Once I TFTP the kernel across, I am okay until I get to "Starting kernel ...",
> then, the UART is "working" in the sense that I get the some characters in the style
> of the kernel starting up, but they are all garbled.
>
> I expect the kernel has started ok, but I am unable to read/write through the UART
> console because of corruptions.
>
> Console log:
> --- 8< ---
> U-Boot 2009.08-00001-gf65536a (Jan 12 2015 - 15:47:19)
>
> CPU: Freescale i.MX6 family TO1.2 at 792 MHz
> Thermal sensor with ratio = 200
> Temperature: 46 C, calibration data 0x5f15527d
huh, it's hot in your office :-)
> mx6q pll1: 792MHz
> mx6q pll2: 528MHz
> mx6q pll3: 480MHz
> mx6q pll8: 50MHz
> ipg clock : 66000000Hz
> ipg per clock : 66000000Hz
> uart clock : 80000000Hz
> cspi clock : 60000000Hz
> ahb clock : 132000000Hz
> axi clock : 264000000Hz
> emi_slow clock: 132000000Hz
> ddr clock : 528000000Hz
> usdhc1 clock : 198000000Hz
> usdhc2 clock : 198000000Hz
> usdhc3 clock : 198000000Hz
> usdhc4 clock : 198000000Hz
> nfc clock : 24000000Hz
> Board: i.MX6Q-SABRESD: unknown-board Board: 0x63012 [WDOG ]
> Boot Device: SD
> I2C: ready
> DRAM: 1 GB
> MMC: FSL_USDHC: 0,FSL_USDHC: 1,FSL_USDHC: 2,FSL_USDHC: 3
> In: serial
> Out: serial
> Err: serial
> Found PFUZE100! deviceid=10,revid=11
> Net: got MAC address from IIM: 00:04:9f:02:e3:0a
> FEC0 [PRIME]
> Hit any key to stop autoboot: 0
> PHY indentify @ 0x1 = 0x004dd074
> FEC: Link is Up 796d
> Using FEC0 device
> TFTP from server 192.168.2.1; our IP address is 192.168.2.2
> Filename 'uImage_dtb.imx6q.v4.12-rc2'.
> Load address: 0x12000000
> Loading: #################################################################
> #################################################################
> #################################################################
> #################################################################
> #################################################################
> #################################################################
> #################################################################
> #################################################################
> #################################################################
> #################################################################
> #################################################################
> #################################################################
> #################################################################
> #################################################################
> #################################################################
> #################################################################
> #################################################################
> ##########################################################
> done
> Bytes transferred = 5951108 (5ace84 hex)
> ## Booting kernel from Legacy Image at 12000000 ...
> Image Name:
> Image Type: ARM Linux Kernel Image (uncompressed)
> Data Size: 5951044 Bytes = 5.7 MB
> Load Address: 10800000
> Entry Point: 10800000
> Verifying Checksum ... OK
> Loading Kernel Image ... OK
> OK
>
> Starting kernel ...
>
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did you check with an oscilloscope if the baud rate is as expected (hmm,
but I wouldn't expect my patch to change the baud rate).
> --- 8< ---
>
> > - Does it make a difference in Linux if the bootloader used the device before?
>
> If you mean, if U-boot uses the UART console before loading the kernel, then no.
> Is that what you mean?
I didn't expect that it destroys the console UART so I expected that you
can make use of a 2nd UART in U-Boot somehow to already initialize the
port and check if that makes it magically work in Linux.
Note to myself: So we're taking about the UART at 0x02020000, it is
operated in DCE mode.
> It makes no difference until the kernel is loaded, then the serial
> output gets corrupted.
>
> > - Can you dump the register space of the uart with v4.12-rc2 and
> > v4.12-rc2 + revert of e61c38d85b7392e?
>
> Difficult to do that I think. The console is unusable in both directions. I can't get any
> response from the console (through typing) once the kernel has started.
ssh or telnet come to mind.
Can you try to just remove the line
writel(0, sport->port.membase + UFCR);
that was introduced in the last hunk by commit e61c38d85b7?
Best regards
Uwe
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