Re: AM5749: tty serial 8250 omap driver crash

[Tony Lindgren <tony@atomide.com>]

Hi,

* Romain Naour <romain.naour@smile.fr> [220204 13:39]:
> It seems that the driver fail to read the UART_LCR register from
> omap8250_set_mctrl():
> 
> "lcr = serial_in(up, UART_LCR);"
> 
> PC is at mem_serial_in+0x2c/0x30
> LR is at omap8250_set_mctrl+0x48/0xb0
> 
> The problem only occurs with a -rt kernel, I tried with several kernel version:
> 5.10-rt, 5.15-rt and 5.17-rt.
> 
> I'm not able to reproduce the issue with a standard kernel.

Interesting, what's the exception you get with the -rt kernel? Is it an
unhandled external abort or something else?

> While looking at the git history, I noticed this commit [3] about "flakey idling
> of uarts and stop using swsup_sidle_act".
> 
> So I removed the SYSC_QUIRK for uart IP revision 0x50411e03 and it fixed my issue.

Hmm.

> Is the SYSC_QUIRK for omap4 still needed ? Is it safe to remove it ?
> It seems this issue was introduced while dropping the legacy platform data
> (between 4.19 and 5.4 kernels).

AFAIK it's still needed, but maybe we can disable it for am57xx though.

Regards,

Tony