1.8V operation of SD1 requires the jumper to be placed on the correct
pins of a connector on these Evaluation Kits. 1.8V is needed to achieve
the higher rated speeds like SDR104. Add a note about it to make sure no
one else spends too much time figuring this out.

Signed-off-by: Cosmin Tanislav <cosmin-gabriel.tanislav.xa@renesas.com>
---
 arch/arm64/boot/dts/renesas/r9a09g077m44-rzt2h-evk.dts | 3 +++
 arch/arm64/boot/dts/renesas/r9a09g087m44-rzn2h-evk.dts | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/arch/arm64/boot/dts/renesas/r9a09g077m44-rzt2h-evk.dts b/arch/arm64/boot/dts/renesas/r9a09g077m44-rzt2h-evk.dts
index e94b84393bd9..7269bca8c8cc 100644
--- a/arch/arm64/boot/dts/renesas/r9a09g077m44-rzt2h-evk.dts
+++ b/arch/arm64/boot/dts/renesas/r9a09g077m44-rzt2h-evk.dts
@@ -26,6 +26,9 @@
  * P17_4 = SD1_CD; SW2[3] = ON
  * P08_5 = SD1_PWEN; SW2[3] = ON
  * P08_6 = SD1_IOVS; SW2[3] = ON; SW5[3] = OFF; SW5[4] = ON
+ * To enable proper operation in 1.8V modes, CN77 must have pins 2 and 3
+ * connected by the jumper. This connects SD1 power-supply control IC output
+ * back to VCC1833_7.
  */
 #define SD1_MICRO_SD	1
 
diff --git a/arch/arm64/boot/dts/renesas/r9a09g087m44-rzn2h-evk.dts b/arch/arm64/boot/dts/renesas/r9a09g087m44-rzn2h-evk.dts
index d27da157c6d6..c87cb6510edc 100644
--- a/arch/arm64/boot/dts/renesas/r9a09g087m44-rzn2h-evk.dts
+++ b/arch/arm64/boot/dts/renesas/r9a09g087m44-rzn2h-evk.dts
@@ -30,6 +30,9 @@
 /*
  * P17_4 = SD1_CD; DSW5[3] = ON; DSW19[1] = OFF; DSW19[2] = ON
  * P08_6 = SD1_IOVS; DSW5[3] = ON
+ * To enable proper operation in 1.8V modes, JP21 must have pins 2 and 3
+ * connected by the jumper. This connects SD1 power-supply control IC output
+ * back to VCC1833_7.
  */
 #define SD1_MICRO_SD	1
 
-- 
2.51.1.dirty

On Wed, 22 Oct 2025 at 09:32, Cosmin Tanislav
<cosmin-gabriel.tanislav.xa@renesas.com> wrote:
> 1.8V operation of SD1 requires the jumper to be placed on the correct
> pins of a connector on these Evaluation Kits. 1.8V is needed to achieve
> the higher rated speeds like SDR104. Add a note about it to make sure no
> one else spends too much time figuring this out.
>
> Signed-off-by: Cosmin Tanislav <cosmin-gabriel.tanislav.xa@renesas.com>

Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
i.e. will queue in renesas-devel for v6.20.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

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