Re: [PATCH 1/7] Revert "tty: serial: fsl_lpuart: drop EARLYCON_DECLARE"

From: Michael Walle
Date: Fri Feb 21 2020 - 04:34:48 EST


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?


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

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.

I've proposed a fix of the underlying problem [1]. But that fix also requires
the EARLYCON_DECLARE() in this driver.