Re: [PATCH] arm64: dts: renesas: r8a779f0: Set UFS lane count

[Geert Uytterhoeven]

Hi Den-san,

CC ufs

Thanks for your patch!

On Fri, 11 Sept 2026 at 09:31, Koichiro Den <den@xxxxxxxxxxxxx> wrote:
> Since commit e72323f3b09f ("scsi: ufs: core: Configure only active lanes
> during link"), the following error is observed on R-Car S4:
>
> ufshcd-renesas e6860000.ufs: Tx lane mismatch [config,reported] [2,1]
> ufshcd-renesas e6860000.ufs: link startup failed -67
> ufshcd-renesas e6860000.ufs: error -ENOLINK: Initialization failed with error -67
> ufshcd-renesas e6860000.ufs: probe with driver ufshcd-renesas failed with error -67

This is very unfortunate...

> R-Car S4 has one UFS lane per direction, as described in section 152.1
> of its hardware manual. Without lanes-per-direction, the UFS platform
> driver defaults to two lanes.
>
> Previously, the core used PA_CONNECTEDRXDATALANES and
> PA_CONNECTEDTXDATALANES to configure the link without checking them
> against lanes-per-direction, so the missing property did not prevent
> initialization.
>
> Explicitly set lanes-per-direction to 1, now that the validation is in
> place.

Given this breaks backwards compatibility with existing DTBs, I think
this new check should be relaxed iff the DT property "lanes-per-direction" is
not present. Are any other platforms affected?
Possible solutions I see are:
  1. Skip the check completely, like commit 06a34d9c1f47b923 ("scsi:
     ufs: core: Skip link param validation when lanes_per_direction is
     unset") does for ufshcd-pci?
  2. Correct hba->lanes_per_direction based on the actual values of
     PA_CONNECTED[RT]XDATALANES?

Alternatively, ufshcd_init_lanes_per_dir() could override
hba->lanes_per_direction to one if "lanes-per-direction" is missing
and the device is compatible with renesas,r8a779f0-ufs.  Or perhaps
hba->lanes_per_direction could be preset in ufs-renesas.c, and not
overwritten by UFSHCD_DEFAULT_LANES_PER_DIRECTION when non-zero?

> Fixes: 5235d551779d ("arm64: dts: renesas: r8a779f0: Add UFS node")
> Cc: stable@xxxxxxxxxxxxxxx # 7.2+
> Signed-off-by: Koichiro Den <den@xxxxxxxxxxxxx>

> --- a/arch/arm64/boot/dts/renesas/r8a779f0.dtsi
> +++ b/arch/arm64/boot/dts/renesas/r8a779f0.dtsi
> @@ -901,6 +901,7 @@ ufs: ufs@e6860000 {
>                         clocks = <&cpg CPG_MOD 1514>, <&ufs30_clk>;
>                         clock-names = "fck", "ref_clk";
>                         freq-table-hz = <200000000 200000000>, <38400000 38400000>;
> +                       lanes-per-direction = <1>;
>                         power-domains = <&sysc R8A779F0_PD_ALWAYS_ON>;
>                         resets = <&cpg 1514>;
>                         status = "disabled";
>

Reviewed-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Works fine on S4SK, so
Tested-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Will queue in renesas-fixes for v7.3.

Gr{oetje,eeting}s,

                        Geert


--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds