[PATCH v5 2/2] serial: mxc: have putc use the TXFIFO

[Fabio Estevam]

Hi Johannes,

On 02/11/2022 09:38, SCHNEIDER Johannes wrote:

> sadly that does not reproduce on imx8mm ... a long print works fine
> with or without the patch :-S

Yes, it does happen on imx8mm.

You need to add the print() inside board_init().

Here is a reproducer on imx8mm evk:

diff --git a/board/freescale/imx8mm_evk/imx8mm_evk.c 
b/board/freescale/imx8mm_evk/imx8mm_evk.c
index e0975fcda705..69ec723c616e 100644
--- a/board/freescale/imx8mm_evk/imx8mm_evk.c
+++ b/board/freescale/imx8mm_evk/imx8mm_evk.c
@@ -50,6 +50,7 @@ int board_init(void)
         if (IS_ENABLED(CONFIG_FEC_MXC))
                 setup_fec();

+       
printf("*******************0123456789012345678901234567890123456789\n");
         return 0;
  }


The result is:

U-Boot SPL 2022.10-00991-gc8d9ff634fc4-dirty (Nov 02 2022 - 11:15:14 
-0300)
No pmic
SEC0:  RNG instantiated
cyclic_register for watchdog at 30280000 failed
WDT:   Failed to start watchdog at 30280000
Trying to boot from MMC1
NOTICE:  BL31: v2.6(release):lf-5.15.32-2.0.0-1-g044ea08c0109
NOTICE:  BL31: Built : 11:15:02, Nov  2 2022


U-Boot 2022.10-00991-gc8d9ff634fc4-dirty (Nov 02 2022 - 11:15:14 -0300)

CPU:   Freescale i.MX8MMQ rev1.0 at 1200 MHz
Reset cause: POR
Model: FSL i.MX8MM EVK board
DRAM:  2 GiB
*******************0123456789012345678901234567890123n�KW�'$HL�� 
devices, 23 uclasses, devicetree: separate
WDT:   Started watchdog at 30280000 with servicing every 1000ms (60s 
timeout)
MMC:   FSL_SDHC: 1, FSL_SDHC: 2
Loading Environment from MMC... OK
In:    serial at 30890000
Out:   serial at 30890000
Err:   serial at 30890000
SEC0:  RNG instantiated
Net:   eth0: ethernet at 30be0000
Hit any key to stop autoboot:  0
u-boot=>

As you can see the corruption is clearly seen.

>> The RTC line is displayed from drivers/misc/gsc.c and the Core: comes
>> from dm_announce. Somehow in between the FIFO does not get drained
>> before dm_announce gets called.
> 
> "flushing" shouldn't be an issue, since everything goes through the
> same set of registers which the imx queues into its fifo...
> i suspect the rootcause lies someplace else?


Reverting your change makes the issue disappear.

Regards,

Fabio Estevam
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