Re: (EXT) Re: [PATCH v2 1/1] arm64: dts: imx8qm: Add fsl, imx7ulp-lpuart compatible to lpuart

Am Montag, dem 22.11.2021 um 09:43 +0800 schrieb Shawn Guo:

On Tue, Nov 16, 2021 at 01:58:14PM +0100, Alexander Stein wrote:

quoted

After commit b4b844930f27 ("tty: serial: fsl_lpuart: drop earlycon
entry
for i.MX8QXP") earlycon support was essentially removed from
imx8qm/imx8qxp due to missing compatible.
The commit message says "i.MX8QXP lpuart is compatible with
i.MX7ULP" so
adding a fallback compatible should be fine.
With this change earlycon is supported again on imx8qm/imx8qxp.

Signed-off-by: Alexander Stein <
alexander.stein@ew.tq-group.com

quoted

Reviewed-by: Peng Fan <
peng.fan@nxp.com

quoted

---
Changes in v2:
* Fix typo in commit message: 'early' -> 'earlycon'

 arch/arm64/boot/dts/freescale/imx8qm-ss-dma.dtsi | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/boot/dts/freescale/imx8qm-ss-dma.dtsi

b/arch/arm64/boot/dts/freescale/imx8qm-ss-dma.dtsi
index bbe5f5ecfb92..3486b99ab6eb 100644

--- a/arch/arm64/boot/dts/freescale/imx8qm-ss-dma.dtsi
+++ b/arch/arm64/boot/dts/freescale/imx8qm-ss-dma.dtsi

@@ -19,19 +19,19 @@ uart4_lpcg: clock-controller@5a4a0000 {
 };
 
 &lpuart0 {
-	compatible = "fsl,imx8qm-lpuart", "fsl,imx8qxp-lpuart";
+	compatible = "fsl,imx8qm-lpuart", "fsl,imx8qxp-lpuart",

"fsl,imx7ulp-lpuart";

Then fsl,imx8qxp-lpuart should be dropped?

If you drop fsl,imx8qxp-lpuart in the compatible list, fsl_lpuart.c
needs a new lpuart_soc_data for imx8qm in order to work. "fsl,imx7ulp-
lpuart" is not enough for imx8qm, as (among other things) "baud" clk is
mising in imx7. IMHO there are 2 ways:

1st
Add both fsl,imx8qxp-lpuart and fsl,imx7ulp-lpuart to the compatible
list to get both regular serial support (fsl,imx8qxp-lpuart) as well as
earlycon (fsl,imx7ulp-lpuart). In this case the bindings need to get
fixed as well, see [1]

2nd
Remove fsl,imx8qxp-lpuart compatible for imx8qm. But in this case
everything done for imx8qxp in fsl_lpuart.c has to be duplicated.
fsl,imx7ulp-lpuart is still required for earlycon support.

If you want to get rid of fsl,imx7ulp-lpuart compatible for
imx8qm/imx8qxp in either case, you need to revert b4b844930f27 ("tty:
serial: fsl_lpuart: drop earlycon entry for i.MX8QXP").

Best regards,
Alexander

[1] 
http://lists.infradead.org/pipermail/linux-arm-kernel/2021-November/697507.html


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