Hi,
Am 2020-02-24 02:12, schrieb Peng Fan:
Subject: Re: [PATCH 1/7] Revert "tty: serial: fsl_lpuart: drop
EARLYCON_DECLARE"
Hi,
Am 2020-02-21 02:30, schrieb Peng Fan:
>> Subject: [PATCH 1/7] Revert "tty: serial: fsl_lpuart: drop
>> EARLYCON_DECLARE"
>>
>> This reverts commit a659652f6169240a5818cb244b280c5a362ef5a4.
>>
>> This broke the earlycon on LS1021A processors because the order of
>> the
>> earlycon_setup() functions were changed. Before the commit the normal
>> lpuart32_early_console_setup() was called. After the commit the
>> lpuart32_imx_early_console_setup() is called instead.
>
> How do you pass earlycon args to kernel?
earlycon=lpuart32,mmio32be,0x2950000,115200
please note that there are two possible declarations: (1) an OF/ACPI
based
earlycon, eg just "earlycon" on the bootargs and (2) an elaborate one
where
you can give the offset and access method yourself, eg. the one from
above.
(1) will still work even with the EARLYCON_DECLARE() removed. But (2)
will
search through all possible
OF_DELARE_EARLYCON(lpuart32,..)
EARLYCON_DECLARE(lpuart32,..)
and doesn't take the compatible into account. So which setup function
is
actually called depends on (a) the order of the OF_DECLARE_EARLYCON()
and
EARLYCON_DECLARE() statements and (b) on the compiler (thats just a
guess!).
For me, the order in which it will actually end up in the
__earlycon_table is
reversed, eg. the last one is called. So now that you've removed the
EARLYCON_DECLARE() the last one is the imx setup function which will
add
the reg offset and doesn't work on LS1021A.
You mean the OF_DECLARD_EARLYCON for i.MX7ULP will be put before
LS1021A
in Image? I am not sure about this. If this is true, you could try
below diff, to see
well, you could have a look at the disassembly; so no need for real
hardware,
if thats what you're missing.
whether it works. i.MX always use little endian.
diff --git a/drivers/tty/serial/fsl_lpuart.c
b/drivers/tty/serial/fsl_lpuart.c
index 91e2805e6441..1b0aa3b836c5 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -2381,8 +2381,10 @@ static int __init
lpuart32_imx_early_console_setup(struct earlycon_device *devic
if (!device->port.membase)
return -ENODEV;
- device->port.iotype = UPIO_MEM32;
- device->port.membase += IMX_REG_OFF;
+ if (device->port.iotype != UPIO_MEM32BE) {
+ device->port.iotype = UPIO_MEM32;
+ device->port.membase += IMX_REG_OFF;
+ }
device->con->write = lpuart32_early_write;
return 0;
while that would also fix the problem (I guess; I'm too lazy to try), it
is
really bad because:
(A) it doesn't fix the underlying problem that there are multiple setup
functions for lpuart32 (and this is not only a problem for
lpuart32)
(B) it would've broken the lpuart32 for IMX in the form (2), if it had
ever
been working.
(C) it will break if some developer adds a new setup function to the
end of
the list
(D) you basically make every setup() function behave like the ls1021a
setup()
if its called in form (2)
Please, lets try to find a more generic solution for this, like my
proposed
patch [1].
-michael
[1]
https://lore.kernel.org/linux-serial/20200220174607.24285-1-michael@xxxxxxxx
