Re: [PATCH] ARM: dts: am33xx: Add missing serial console speed

Den tors. 2. okt. 2025 kl. 14.32 skrev Matti Vaittinen
[off-list ref]:

On 02/10/2025 12:53, Geert Uytterhoeven wrote:

quoted

Without a serial console speed specified in chosen/stdout-path in the
DTB, the serial console uses the default speed of the serial driver,
unless explicitly overridden in a legacy console= kernel command-line
parameter.

After dropping "ti,omap3-uart" from the list of compatible values in DT,
AM33xx serial ports can no longer be used with the legacy OMAP serial
driver, but only with the OMAP-flavored 8250 serial driver (which is
mutually-exclusive with the former).  However, replacing
CONFIG_SERIAL_OMAP=y by CONFIG_SERIAL_8250_OMAP=y (with/without enabling
CONFIG_SERIAL_8250_OMAP_TTYO_FIXUP) may not be sufficient to restore
serial console functionality: the legacy OMAP serial driver defaults to
115200 bps, while the 8250 serial driver defaults to 9600 bps, causing
no visible output on the serial console when no appropriate console=
kernel command-line parameter is specified.

Fix this for all AM33xx boards by adding ":115200n8" to
chosen/stdout-path.  This requires replacing the "&uartN" reference by
the corresponding "serialN" DT alias.

Fixes: ca8be8fc2c306efb ("ARM: dts: am33xx-l4: fix UART compatible")
Fixes: 077e1cde78c3f904 ("ARM: omap2plus_defconfig: Enable 8250_OMAP")
Closes: https://lore.kernel.org/CAMuHMdUb7Jb2=GqK3=Rn+Gv5G9KogcQieqDvjDCkJA4zyX4VcA@mail.gmail.com (local)
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

Reviewed-by: Matti Vaittinen <mazziesaccount@gmail.com>
Tested-by: Matti Vaittinen <mazziesaccount@gmail.com>

Reviewed-by: Bruno Thomsen <redacted>

(Tested booting on Beaglebone black with a config and kernel command
line which were NOT affected by the issue. Well, prints do still get
through the UART to my minicom, so things seem to work for me after this
change as well :) )

The change does also look Ok to me.

Yours,
        -- Matti