[PATCH v2 0/3] Support UART over MicroSD slot on Transformer T20

[PATCH v2 0/3] Support UART over MicroSD slot on Transformer T20

[Artur Kowalski]

v2 no longer forces UARTA to SDB/SDD on Transformer 20. Instead
CONFIG_TEGRA_UARTA_MICROSD is used for this purpose. Additionally,
user does not needs to configure additional DT files as that is handled
internally with preprocessor directives.

Changes in v2:
- fixed indentation of preprocessor directives
- added TEGRA_UARTA_MICROSD Kconfig option
- removed .dtsi for enabling UART over microSD
- modified transformer DT to use UARTA and correct pinmux when
  TEGRA_UARTA_MICROSD is enabled; it is enough to flip a single
  switch to enable/disable UART over microSD

Artur Kowalski (3):
  tegra: add funcmux for exposing UART over uSD slot on Tegra 20
  tegra: respect CONFIG_TEGRA_ENABLE_UART* options on Transformer T20
  tegra: allow to expose UART on microSD slot

 arch/arm/dts/tegra20-asus-transformer.dtsi  | 24 +++++++++++++++++++++
 arch/arm/include/asm/arch-tegra20/funcmux.h |  1 +
 arch/arm/mach-tegra/board.c                 |  2 ++
 arch/arm/mach-tegra/tegra20/Kconfig         | 18 ++++++++++++++++
 drivers/pinctrl/tegra/funcmux-tegra20.c     |  9 +++++++-
 include/configs/transformer-t20.h           | 10 +++++++++
 6 files changed, 63 insertions(+), 1 deletion(-)

-- 
2.48.1

[PATCH v2 1/3] tegra: add funcmux for exposing UART over uSD slot on Tegra 20

[Artur Kowalski]

UART-A can be exposed through uSD, this was tested on Transformer T20
but should work on all Ventana-based boards.

TX is exported on SDD pingroup corresponding to uSD CLK pin
RX is exported on SDB which is CMD pin in uSD slot

Signed-off-by: Artur Kowalski <arturkow2000@gmail.com>
---

Changes in v2:
- fixed indentation of preprocessor directives

 arch/arm/include/asm/arch-tegra20/funcmux.h | 1 +
 arch/arm/mach-tegra/board.c                 | 2 ++
 arch/arm/mach-tegra/tegra20/Kconfig         | 3 +++
 drivers/pinctrl/tegra/funcmux-tegra20.c     | 9 ++++++++-
 4 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/arch/arm/include/asm/arch-tegra20/funcmux.h b/arch/arm/include/asm/arch-tegra20/funcmux.h
index e9e96c1f933..bafcf857620 100644
--- a/arch/arm/include/asm/arch-tegra20/funcmux.h
+++ b/arch/arm/include/asm/arch-tegra20/funcmux.h
@@ -19,6 +19,7 @@ enum {
 	FUNCMUX_UART1_UAA_UAB,
 	FUNCMUX_UART1_GPU,
 	FUNCMUX_UART1_SDIO1,
+	FUNCMUX_UART1_SDB_SDD,
 	FUNCMUX_UART2_UAD = 0,
 	FUNCMUX_UART4_GMC = 0,
 
diff --git a/arch/arm/mach-tegra/board.c b/arch/arm/mach-tegra/board.c
index 7ca56a3b081..7597034fa48 100644
--- a/arch/arm/mach-tegra/board.c
+++ b/arch/arm/mach-tegra/board.c
@@ -169,6 +169,8 @@ static int uart_configs[] = {
 	FUNCMUX_UART1_GPU,
  #elif defined(CONFIG_TEGRA_UARTA_SDIO1)
 	FUNCMUX_UART1_SDIO1,
+ #elif defined(CONFIG_TEGRA_UARTA_SDB_SDD)
+	FUNCMUX_UART1_SDB_SDD,
  #else
 	FUNCMUX_UART1_IRRX_IRTX,
 #endif
diff --git a/arch/arm/mach-tegra/tegra20/Kconfig b/arch/arm/mach-tegra/tegra20/Kconfig
index e2735d93e28..3349f1e2786 100644
--- a/arch/arm/mach-tegra/tegra20/Kconfig
+++ b/arch/arm/mach-tegra/tegra20/Kconfig
@@ -17,6 +17,9 @@ config TEGRA_UARTA_GPU
 config TEGRA_UARTA_SDIO1
 	bool
 
+config TEGRA_UARTA_SDB_SDD
+	bool
+
 choice
 	prompt "Tegra20 board select"
 	optional
diff --git a/drivers/pinctrl/tegra/funcmux-tegra20.c b/drivers/pinctrl/tegra/funcmux-tegra20.c
index 951ae196161..f60d5aad3a4 100644
--- a/drivers/pinctrl/tegra/funcmux-tegra20.c
+++ b/drivers/pinctrl/tegra/funcmux-tegra20.c
@@ -62,8 +62,15 @@ int funcmux_select(enum periph_id id, int config)
 			pinmux_tristate_disable(PMUX_PINGRP_SDIO1);
 			bad_config = 0;
 			break;
+		case FUNCMUX_UART1_SDB_SDD:
+			pinmux_set_func(PMUX_PINGRP_SDB, PMUX_FUNC_UARTA);
+			pinmux_set_func(PMUX_PINGRP_SDD, PMUX_FUNC_UARTA);
+			pinmux_tristate_disable(PMUX_PINGRP_SDB);
+			pinmux_tristate_disable(PMUX_PINGRP_SDD);
+			bad_config = 0;
+			break;
 		}
-		if (!bad_config) {
+		if (!bad_config && config != FUNCMUX_UART1_SDB_SDD) {
 			/*
 			 * Tegra appears to boot with function UARTA pre-
 			 * selected on mux group SDB. If two mux groups are
-- 
2.48.1

Re: [PATCH v2 1/3] tegra: add funcmux for exposing UART over uSD slot on Tegra 20

[Svyatoslav Ryhel]

нд, 30 бер. 2025 р. о 22:27 Artur Kowalski <arturkow2000@gmail.com> пише:
>
> UART-A can be exposed through uSD, this was tested on Transformer T20
> but should work on all Ventana-based boards.
>
> TX is exported on SDD pingroup corresponding to uSD CLK pin
> RX is exported on SDB which is CMD pin in uSD slot
>
> Signed-off-by: Artur Kowalski <arturkow2000@gmail.com>
> ---
>
> Changes in v2:
> - fixed indentation of preprocessor directives
>
>  arch/arm/include/asm/arch-tegra20/funcmux.h | 1 +
>  arch/arm/mach-tegra/board.c                 | 2 ++
>  arch/arm/mach-tegra/tegra20/Kconfig         | 3 +++
>  drivers/pinctrl/tegra/funcmux-tegra20.c     | 9 ++++++++-
>  4 files changed, 14 insertions(+), 1 deletion(-)
>

Reviewed-by: Svyatoslav Ryhel <clamor95@gmail.com>

Re: [PATCH v2 1/3] tegra: add funcmux for exposing UART over uSD slot on Tegra 20

[Svyatoslav Ryhel]

пн, 31 бер. 2025 р. о 08:42 Svyatoslav Ryhel <clamor95@gmail.com> пише:
>
> нд, 30 бер. 2025 р. о 22:27 Artur Kowalski <arturkow2000@gmail.com> пише:
> >
> > UART-A can be exposed through uSD, this was tested on Transformer T20
> > but should work on all Ventana-based boards.
> >
> > TX is exported on SDD pingroup corresponding to uSD CLK pin
> > RX is exported on SDB which is CMD pin in uSD slot
> >
> > Signed-off-by: Artur Kowalski <arturkow2000@gmail.com>
> > ---
> >
> > Changes in v2:
> > - fixed indentation of preprocessor directives
> >
> >  arch/arm/include/asm/arch-tegra20/funcmux.h | 1 +
> >  arch/arm/mach-tegra/board.c                 | 2 ++
> >  arch/arm/mach-tegra/tegra20/Kconfig         | 3 +++
> >  drivers/pinctrl/tegra/funcmux-tegra20.c     | 9 ++++++++-
> >  4 files changed, 14 insertions(+), 1 deletion(-)
> >
>
> Reviewed-by: Svyatoslav Ryhel <clamor95@gmail.com>

Applied to u-boot-tegra/staging.
Thank you.

[PATCH v2 2/3] tegra: respect CONFIG_TEGRA_ENABLE_UART* options on Transformer T20

[Artur Kowalski]

If debug UART is set to anything other than UARTD, U-Boot's SPL hangs
trying to communicate with UARTD which clock won't be ungated. With this
patch it is possible to boot with UARTA enabled.

Signed-off-by: Artur Kowalski <arturkow2000@gmail.com>
---

(no changes since v1)

 include/configs/transformer-t20.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/include/configs/transformer-t20.h b/include/configs/transformer-t20.h
index 6a3d9b24036..d3a98cc5a70 100644
--- a/include/configs/transformer-t20.h
+++ b/include/configs/transformer-t20.h
@@ -16,7 +16,17 @@
 #define CFG_TEGRA_BOARD_STRING		"ASUS Transformer"
 
 /* Board-specific serial config */
+#if defined(CONFIG_TEGRA_ENABLE_UARTA)
+#define CFG_SYS_NS16550_COM1		NV_PA_APB_UARTA_BASE
+#elif defined(CONFIG_TEGRA_ENABLE_UARTB)
+#define CFG_SYS_NS16550_COM1		NV_PA_APB_UARTB_BASE
+#elif defined(CONFIG_TEGRA_ENABLE_UARTC)
+#define CFG_SYS_NS16550_COM1		NV_PA_APB_UARCD_BASE
+#elif defined(CONFIG_TEGRA_ENABLE_UARTD)
 #define CFG_SYS_NS16550_COM1		NV_PA_APB_UARTD_BASE
+#elif defined(CONFIG_TEGRA_ENABLE_UARTE)
+#define CFG_SYS_NS16550_COM1		NV_PA_APB_UARTE_BASE
+#endif
 
 #include "tegra-common-post.h"
 
-- 
2.48.1

Re: [PATCH v2 2/3] tegra: respect CONFIG_TEGRA_ENABLE_UART* options on Transformer T20

[Svyatoslav Ryhel]

нд, 30 бер. 2025 р. о 22:27 Artur Kowalski <arturkow2000@gmail.com> пише:
>
> If debug UART is set to anything other than UARTD, U-Boot's SPL hangs
> trying to communicate with UARTD which clock won't be ungated. With this
> patch it is possible to boot with UARTA enabled.
>
> Signed-off-by: Artur Kowalski <arturkow2000@gmail.com>
> ---
>
> (no changes since v1)
>
>  include/configs/transformer-t20.h | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/include/configs/transformer-t20.h b/include/configs/transformer-t20.h
> index 6a3d9b24036..d3a98cc5a70 100644
> --- a/include/configs/transformer-t20.h
> +++ b/include/configs/transformer-t20.h
> @@ -16,7 +16,17 @@
>  #define CFG_TEGRA_BOARD_STRING         "ASUS Transformer"
>
>  /* Board-specific serial config */
> +#if defined(CONFIG_TEGRA_ENABLE_UARTA)
> +#define CFG_SYS_NS16550_COM1           NV_PA_APB_UARTA_BASE
> +#elif defined(CONFIG_TEGRA_ENABLE_UARTB)
> +#define CFG_SYS_NS16550_COM1           NV_PA_APB_UARTB_BASE
> +#elif defined(CONFIG_TEGRA_ENABLE_UARTC)
> +#define CFG_SYS_NS16550_COM1           NV_PA_APB_UARCD_BASE
> +#elif defined(CONFIG_TEGRA_ENABLE_UARTD)
>  #define CFG_SYS_NS16550_COM1           NV_PA_APB_UARTD_BASE
> +#elif defined(CONFIG_TEGRA_ENABLE_UARTE)
> +#define CFG_SYS_NS16550_COM1           NV_PA_APB_UARTE_BASE
> +#endif
>

Here you are actually hitting much much deeper thing. You are applying
fix to the result, not the cause. Adjustment should be done in the
tegra board itself with amending all existing tegra boards. As a
maintainer I cannot insist on you doing this unless you willingly
agree. You have time to answer till 02.03.25 and if no answer I will
apply patch on my own to custodian tegra/staging branch.

>  #include "tegra-common-post.h"
>
> --
> 2.48.1
>

Re: [PATCH v2 2/3] tegra: respect CONFIG_TEGRA_ENABLE_UART* options on Transformer T20

[Artur Kowalski]

W dniu 31.03.2025 o 07:48, Svyatoslav Ryhel pisze:
> нд, 30 бер. 2025 р. о 22:27 Artur Kowalski <arturkow2000@gmail.com> пише:
>> If debug UART is set to anything other than UARTD, U-Boot's SPL hangs
>> trying to communicate with UARTD which clock won't be ungated. With this
>> patch it is possible to boot with UARTA enabled.
>>
>> Signed-off-by: Artur Kowalski <arturkow2000@gmail.com>
>> ---
>>
>> (no changes since v1)
>>
>>   include/configs/transformer-t20.h | 10 ++++++++++
>>   1 file changed, 10 insertions(+)
>>
>> diff --git a/include/configs/transformer-t20.h b/include/configs/transformer-t20.h
>> index 6a3d9b24036..d3a98cc5a70 100644
>> --- a/include/configs/transformer-t20.h
>> +++ b/include/configs/transformer-t20.h
>> @@ -16,7 +16,17 @@
>>   #define CFG_TEGRA_BOARD_STRING         "ASUS Transformer"
>>
>>   /* Board-specific serial config */
>> +#if defined(CONFIG_TEGRA_ENABLE_UARTA)
>> +#define CFG_SYS_NS16550_COM1           NV_PA_APB_UARTA_BASE
>> +#elif defined(CONFIG_TEGRA_ENABLE_UARTB)
>> +#define CFG_SYS_NS16550_COM1           NV_PA_APB_UARTB_BASE
>> +#elif defined(CONFIG_TEGRA_ENABLE_UARTC)
>> +#define CFG_SYS_NS16550_COM1           NV_PA_APB_UARCD_BASE
>> +#elif defined(CONFIG_TEGRA_ENABLE_UARTD)
>>   #define CFG_SYS_NS16550_COM1           NV_PA_APB_UARTD_BASE
>> +#elif defined(CONFIG_TEGRA_ENABLE_UARTE)
>> +#define CFG_SYS_NS16550_COM1           NV_PA_APB_UARTE_BASE
>> +#endif
>>
> Here you are actually hitting much much deeper thing. You are applying
> fix to the result, not the cause. Adjustment should be done in the
> tegra board itself with amending all existing tegra boards. As a
> maintainer I cannot insist on you doing this unless you willingly
> agree. You have time to answer till 02.03.25 and if no answer I will
> apply patch on my own to custodian tegra/staging branch.
I'd like to do it but unfortunately I won't have enought time this week.
>>   #include "tegra-common-post.h"
>>
>> --
>> 2.48.1
>>

Re: [PATCH v2 2/3] tegra: respect CONFIG_TEGRA_ENABLE_UART* options on Transformer T20

[Svyatoslav Ryhel]

вт, 1 квіт. 2025 р. о 16:30 Artur Kowalski <arturkow2000@gmail.com> пише:
>
>
> W dniu 31.03.2025 o 07:48, Svyatoslav Ryhel pisze:
> > нд, 30 бер. 2025 р. о 22:27 Artur Kowalski <arturkow2000@gmail.com> пише:
> >> If debug UART is set to anything other than UARTD, U-Boot's SPL hangs
> >> trying to communicate with UARTD which clock won't be ungated. With this
> >> patch it is possible to boot with UARTA enabled.
> >>
> >> Signed-off-by: Artur Kowalski <arturkow2000@gmail.com>
> >> ---
> >>
> >> (no changes since v1)
> >>
> >>   include/configs/transformer-t20.h | 10 ++++++++++
> >>   1 file changed, 10 insertions(+)
> >>
> >> diff --git a/include/configs/transformer-t20.h b/include/configs/transformer-t20.h
> >> index 6a3d9b24036..d3a98cc5a70 100644
> >> --- a/include/configs/transformer-t20.h
> >> +++ b/include/configs/transformer-t20.h
> >> @@ -16,7 +16,17 @@
> >>   #define CFG_TEGRA_BOARD_STRING         "ASUS Transformer"
> >>
> >>   /* Board-specific serial config */
> >> +#if defined(CONFIG_TEGRA_ENABLE_UARTA)
> >> +#define CFG_SYS_NS16550_COM1           NV_PA_APB_UARTA_BASE
> >> +#elif defined(CONFIG_TEGRA_ENABLE_UARTB)
> >> +#define CFG_SYS_NS16550_COM1           NV_PA_APB_UARTB_BASE
> >> +#elif defined(CONFIG_TEGRA_ENABLE_UARTC)
> >> +#define CFG_SYS_NS16550_COM1           NV_PA_APB_UARCD_BASE
> >> +#elif defined(CONFIG_TEGRA_ENABLE_UARTD)
> >>   #define CFG_SYS_NS16550_COM1           NV_PA_APB_UARTD_BASE
> >> +#elif defined(CONFIG_TEGRA_ENABLE_UARTE)
> >> +#define CFG_SYS_NS16550_COM1           NV_PA_APB_UARTE_BASE
> >> +#endif
> >>
> > Here you are actually hitting much much deeper thing. You are applying
> > fix to the result, not the cause. Adjustment should be done in the
> > tegra board itself with amending all existing tegra boards. As a
> > maintainer I cannot insist on you doing this unless you willingly
> > agree. You have time to answer till 02.03.25 and if no answer I will
> > apply patch on my own to custodian tegra/staging branch.
> I'd like to do it but unfortunately I won't have enought time this week.

Thanks for responding. Don't worry, I was planning to remove
per-device headers anyway so I will include you into patchset which
should address the root of this issue you are facing.

> >>   #include "tegra-common-post.h"
> >>
> >> --
> >> 2.48.1
> >>

[PATCH v2 3/3] tegra: allow to expose UART on microSD slot

[Artur Kowalski]

Tegra20 has mux allowing to repurpose microSD as UART on boards which
use sdmmc3 controller for microSD. Add TEGRA_UARTA_MICROSD to enable
this feature. It is currently supported on Transformer T20, support for
other boards may require Device Tree changes.

Update Transformer T20 DTS to select correct pinmux and stdout-path
based on TEGRA_UARTA_MICROSD.

Signed-off-by: Artur Kowalski <arturkow2000@gmail.com>
---

Changes in v2:
- added TEGRA_UARTA_MICROSD Kconfig option
- removed .dtsi for enabling UART over microSD
- modified transformer DT to use UARTA and correct pinmux when
  TEGRA_UARTA_MICROSD is enabled; it is enough to flip a single
  switch to enable/disable UART over microSD

 arch/arm/dts/tegra20-asus-transformer.dtsi | 24 ++++++++++++++++++++++
 arch/arm/mach-tegra/tegra20/Kconfig        | 15 ++++++++++++++
 2 files changed, 39 insertions(+)

diff --git a/arch/arm/dts/tegra20-asus-transformer.dtsi b/arch/arm/dts/tegra20-asus-transformer.dtsi
index 49efabbfd92..9ea323c81f3 100644
--- a/arch/arm/dts/tegra20-asus-transformer.dtsi
+++ b/arch/arm/dts/tegra20-asus-transformer.dtsi
@@ -5,7 +5,13 @@
 
 / {
 	chosen {
+#if CONFIG_IS_ENABLED(TEGRA_ENABLE_UARTA)
+		stdout-path = &uarta;
+#elif CONFIG_IS_ENABLED(TEGRA_ENABLE_UARTD)
 		stdout-path = &uartd;
+#else
+#error Unsupported UART
+#endif
 	};
 
 	aliases {
@@ -195,10 +201,17 @@
 				nvidia,function = "i2c1";
 			};
 
+#if CONFIG_IS_ENABLED(TEGRA_UARTA_SDB_SDD)
+			dbguart {
+				nvidia,pins = "sdb", "sdd";
+				nvidia,function = "uarta";
+			};
+#else
 			sdb {
 				nvidia,pins = "sdb", "sdc", "sdd", "slxc", "slxk";
 				nvidia,function = "sdio3";
 			};
+#endif
 
 			sdio1 {
 				nvidia,pins = "sdio1";
@@ -376,7 +389,13 @@
 		};
 	};
 
+#if CONFIG_IS_ENABLED(TEGRA_ENABLE_UARTA)
+	uarta: serial@70006000 {
+#elif CONFIG_IS_ENABLED(TEGRA_ENABLE_UARTD)
 	uartd: serial@70006300 {
+#else
+#error Unsupported UART
+#endif
 		status = "okay";
 		clock-frequency = <216000000>;
 	};
@@ -434,7 +453,12 @@
 	};
 
 	sdmmc3: sdhci@c8000400 {
+#if CONFIG_IS_ENABLED(TEGRA_UARTA_MICROSD)
+		/* Can't use both at the same time */
+		status = "disabled";
+#else
 		status = "okay";
+#endif
 		bus-width = <4>;
 
 		cd-gpios = <&gpio TEGRA_GPIO(I, 5) GPIO_ACTIVE_LOW>;
diff --git a/arch/arm/mach-tegra/tegra20/Kconfig b/arch/arm/mach-tegra/tegra20/Kconfig
index 3349f1e2786..c2c51660216 100644
--- a/arch/arm/mach-tegra/tegra20/Kconfig
+++ b/arch/arm/mach-tegra/tegra20/Kconfig
@@ -77,6 +77,21 @@ endchoice
 config SYS_SOC
 	default "tegra20"
 
+config TEGRA_UARTA_MICROSD
+	bool "UARTA on MicroSD breakout board"
+	default n
+	depends on TEGRA_ENABLE_UARTA && TARGET_TRANSFORMER_T20
+	select TEGRA_UARTA_SDB_SDD
+	help
+	  Repurpose the SD card slot for getting access to the UARTA serial
+	  console. Primarily useful only for low level u-boot debugging on
+	  tablets, where normal UARTD is difficult to access and requires
+	  device disassembly and/or soldering. Enabling this option causes
+	  UARTA TX to become exposed on SDD and RX on SDB pins which correspond
+	  to microSD CLK and CMD pins respectively. Currently this is supported
+	  only on Transformer T20, support for other platforms may require DT
+	  and configs (from include/configs/*) updates.
+
 source "board/nvidia/harmony/Kconfig"
 source "board/avionic-design/medcom-wide/Kconfig"
 source "board/compal/paz00/Kconfig"
-- 
2.48.1

Re: [PATCH v2 3/3] tegra: allow to expose UART on microSD slot

[Svyatoslav Ryhel]

нд, 30 бер. 2025 р. о 22:27 Artur Kowalski <arturkow2000@gmail.com> пише:
>
> Tegra20 has mux allowing to repurpose microSD as UART on boards which
> use sdmmc3 controller for microSD. Add TEGRA_UARTA_MICROSD to enable
> this feature. It is currently supported on Transformer T20, support for
> other boards may require Device Tree changes.
>
> Update Transformer T20 DTS to select correct pinmux and stdout-path
> based on TEGRA_UARTA_MICROSD.
>
> Signed-off-by: Artur Kowalski <arturkow2000@gmail.com>
> ---
>
> Changes in v2:
> - added TEGRA_UARTA_MICROSD Kconfig option
> - removed .dtsi for enabling UART over microSD
> - modified transformer DT to use UARTA and correct pinmux when
>   TEGRA_UARTA_MICROSD is enabled; it is enough to flip a single
>   switch to enable/disable UART over microSD
>
>  arch/arm/dts/tegra20-asus-transformer.dtsi | 24 ++++++++++++++++++++++
>  arch/arm/mach-tegra/tegra20/Kconfig        | 15 ++++++++++++++
>  2 files changed, 39 insertions(+)
>
> diff --git a/arch/arm/dts/tegra20-asus-transformer.dtsi b/arch/arm/dts/tegra20-asus-transformer.dtsi
> index 49efabbfd92..9ea323c81f3 100644
> --- a/arch/arm/dts/tegra20-asus-transformer.dtsi
> +++ b/arch/arm/dts/tegra20-asus-transformer.dtsi
> @@ -5,7 +5,13 @@
>
>  / {
>         chosen {
> +#if CONFIG_IS_ENABLED(TEGRA_ENABLE_UARTA)
> +               stdout-path = &uarta;
> +#elif CONFIG_IS_ENABLED(TEGRA_ENABLE_UARTD)
>                 stdout-path = &uartd;
> +#else
> +#error Unsupported UART
> +#endif
>         };
>
>         aliases {
> @@ -195,10 +201,17 @@
>                                 nvidia,function = "i2c1";
>                         };
>
> +#if CONFIG_IS_ENABLED(TEGRA_UARTA_SDB_SDD)
> +                       dbguart {
> +                               nvidia,pins = "sdb", "sdd";
> +                               nvidia,function = "uarta";
> +                       };
> +#else
>                         sdb {
>                                 nvidia,pins = "sdb", "sdc", "sdd", "slxc", "slxk";
>                                 nvidia,function = "sdio3";
>                         };
> +#endif
>
>                         sdio1 {
>                                 nvidia,pins = "sdio1";
> @@ -376,7 +389,13 @@
>                 };
>         };
>
> +#if CONFIG_IS_ENABLED(TEGRA_ENABLE_UARTA)
> +       uarta: serial@70006000 {
> +#elif CONFIG_IS_ENABLED(TEGRA_ENABLE_UARTD)
>         uartd: serial@70006300 {
> +#else
> +#error Unsupported UART
> +#endif
>                 status = "okay";
>                 clock-frequency = <216000000>;
>         };
> @@ -434,7 +453,12 @@
>         };
>
>         sdmmc3: sdhci@c8000400 {
> +#if CONFIG_IS_ENABLED(TEGRA_UARTA_MICROSD)
> +               /* Can't use both at the same time */
> +               status = "disabled";
> +#else
>                 status = "okay";
> +#endif
>                 bus-width = <4>;
>
>                 cd-gpios = <&gpio TEGRA_GPIO(I, 5) GPIO_ACTIVE_LOW>;
> diff --git a/arch/arm/mach-tegra/tegra20/Kconfig b/arch/arm/mach-tegra/tegra20/Kconfig
> index 3349f1e2786..c2c51660216 100644
> --- a/arch/arm/mach-tegra/tegra20/Kconfig
> +++ b/arch/arm/mach-tegra/tegra20/Kconfig
> @@ -77,6 +77,21 @@ endchoice
>  config SYS_SOC
>         default "tegra20"
>
> +config TEGRA_UARTA_MICROSD
> +       bool "UARTA on MicroSD breakout board"
> +       default n
> +       depends on TEGRA_ENABLE_UARTA && TARGET_TRANSFORMER_T20
> +       select TEGRA_UARTA_SDB_SDD
> +       help
> +         Repurpose the SD card slot for getting access to the UARTA serial
> +         console. Primarily useful only for low level u-boot debugging on
> +         tablets, where normal UARTD is difficult to access and requires
> +         device disassembly and/or soldering. Enabling this option causes
> +         UARTA TX to become exposed on SDD and RX on SDB pins which correspond
> +         to microSD CLK and CMD pins respectively. Currently this is supported
> +         only on Transformer T20, support for other platforms may require DT
> +         and configs (from include/configs/*) updates.
> +
>  source "board/nvidia/harmony/Kconfig"
>  source "board/avionic-design/medcom-wide/Kconfig"
>  source "board/compal/paz00/Kconfig"
> --
> 2.48.1
>

This is not applicable since this is a hack by nature, BUT if you
contain this in the transformer t20 board and Kconfig (no dts
changes), this may be applied.

Re: [PATCH v2 3/3] tegra: allow to expose UART on microSD slot

[Artur Kowalski]

W dniu 31.03.2025 o 07:51, Svyatoslav Ryhel pisze:
> нд, 30 бер. 2025 р. о 22:27 Artur Kowalski <arturkow2000@gmail.com> пише:
>> Tegra20 has mux allowing to repurpose microSD as UART on boards which
>> use sdmmc3 controller for microSD. Add TEGRA_UARTA_MICROSD to enable
>> this feature. It is currently supported on Transformer T20, support for
>> other boards may require Device Tree changes.
>>
>> Update Transformer T20 DTS to select correct pinmux and stdout-path
>> based on TEGRA_UARTA_MICROSD.
>>
>> Signed-off-by: Artur Kowalski <arturkow2000@gmail.com>
>> ---
>>
>> Changes in v2:
>> - added TEGRA_UARTA_MICROSD Kconfig option
>> - removed .dtsi for enabling UART over microSD
>> - modified transformer DT to use UARTA and correct pinmux when
>>    TEGRA_UARTA_MICROSD is enabled; it is enough to flip a single
>>    switch to enable/disable UART over microSD
>>
>>   arch/arm/dts/tegra20-asus-transformer.dtsi | 24 ++++++++++++++++++++++
>>   arch/arm/mach-tegra/tegra20/Kconfig        | 15 ++++++++++++++
>>   2 files changed, 39 insertions(+)
>>
>> diff --git a/arch/arm/dts/tegra20-asus-transformer.dtsi b/arch/arm/dts/tegra20-asus-transformer.dtsi
>> index 49efabbfd92..9ea323c81f3 100644
>> --- a/arch/arm/dts/tegra20-asus-transformer.dtsi
>> +++ b/arch/arm/dts/tegra20-asus-transformer.dtsi
>> @@ -5,7 +5,13 @@
>>
>>   / {
>>          chosen {
>> +#if CONFIG_IS_ENABLED(TEGRA_ENABLE_UARTA)
>> +               stdout-path = &uarta;
>> +#elif CONFIG_IS_ENABLED(TEGRA_ENABLE_UARTD)
>>                  stdout-path = &uartd;
>> +#else
>> +#error Unsupported UART
>> +#endif
>>          };
>>
>>          aliases {
>> @@ -195,10 +201,17 @@
>>                                  nvidia,function = "i2c1";
>>                          };
>>
>> +#if CONFIG_IS_ENABLED(TEGRA_UARTA_SDB_SDD)
>> +                       dbguart {
>> +                               nvidia,pins = "sdb", "sdd";
>> +                               nvidia,function = "uarta";
>> +                       };
>> +#else
>>                          sdb {
>>                                  nvidia,pins = "sdb", "sdc", "sdd", "slxc", "slxk";
>>                                  nvidia,function = "sdio3";
>>                          };
>> +#endif
>>
>>                          sdio1 {
>>                                  nvidia,pins = "sdio1";
>> @@ -376,7 +389,13 @@
>>                  };
>>          };
>>
>> +#if CONFIG_IS_ENABLED(TEGRA_ENABLE_UARTA)
>> +       uarta: serial@70006000 {
>> +#elif CONFIG_IS_ENABLED(TEGRA_ENABLE_UARTD)
>>          uartd: serial@70006300 {
>> +#else
>> +#error Unsupported UART
>> +#endif
>>                  status = "okay";
>>                  clock-frequency = <216000000>;
>>          };
>> @@ -434,7 +453,12 @@
>>          };
>>
>>          sdmmc3: sdhci@c8000400 {
>> +#if CONFIG_IS_ENABLED(TEGRA_UARTA_MICROSD)
>> +               /* Can't use both at the same time */
>> +               status = "disabled";
>> +#else
>>                  status = "okay";
>> +#endif
>>                  bus-width = <4>;
>>
>>                  cd-gpios = <&gpio TEGRA_GPIO(I, 5) GPIO_ACTIVE_LOW>;
>> diff --git a/arch/arm/mach-tegra/tegra20/Kconfig b/arch/arm/mach-tegra/tegra20/Kconfig
>> index 3349f1e2786..c2c51660216 100644
>> --- a/arch/arm/mach-tegra/tegra20/Kconfig
>> +++ b/arch/arm/mach-tegra/tegra20/Kconfig
>> @@ -77,6 +77,21 @@ endchoice
>>   config SYS_SOC
>>          default "tegra20"
>>
>> +config TEGRA_UARTA_MICROSD
>> +       bool "UARTA on MicroSD breakout board"
>> +       default n
>> +       depends on TEGRA_ENABLE_UARTA && TARGET_TRANSFORMER_T20
>> +       select TEGRA_UARTA_SDB_SDD
>> +       help
>> +         Repurpose the SD card slot for getting access to the UARTA serial
>> +         console. Primarily useful only for low level u-boot debugging on
>> +         tablets, where normal UARTD is difficult to access and requires
>> +         device disassembly and/or soldering. Enabling this option causes
>> +         UARTA TX to become exposed on SDD and RX on SDB pins which correspond
>> +         to microSD CLK and CMD pins respectively. Currently this is supported
>> +         only on Transformer T20, support for other platforms may require DT
>> +         and configs (from include/configs/*) updates.
>> +
>>   source "board/nvidia/harmony/Kconfig"
>>   source "board/avionic-design/medcom-wide/Kconfig"
>>   source "board/compal/paz00/Kconfig"
>> --
>> 2.48.1
>>
> This is not applicable since this is a hack by nature, BUT if you
> contain this in the transformer t20 board and Kconfig (no dts
> changes), this may be applied.
Ok, then I'll drop DTS changes. I will add few words about this option 
in Transformer documentation
and a note in Kconfig help to not surprise users with not booting U-Boot 
as enabling this option without
changing DTS causes U-Boot to hang.

Re: [PATCH v2 3/3] tegra: allow to expose UART on microSD slot

[Svyatoslav Ryhel]

вт, 1 квіт. 2025 р. о 16:34 Artur Kowalski <arturkow2000@gmail.com> пише:
>
>
> W dniu 31.03.2025 o 07:51, Svyatoslav Ryhel pisze:
> > нд, 30 бер. 2025 р. о 22:27 Artur Kowalski <arturkow2000@gmail.com> пише:
> >> Tegra20 has mux allowing to repurpose microSD as UART on boards which
> >> use sdmmc3 controller for microSD. Add TEGRA_UARTA_MICROSD to enable
> >> this feature. It is currently supported on Transformer T20, support for
> >> other boards may require Device Tree changes.
> >>
> >> Update Transformer T20 DTS to select correct pinmux and stdout-path
> >> based on TEGRA_UARTA_MICROSD.
> >>
> >> Signed-off-by: Artur Kowalski <arturkow2000@gmail.com>
> >> ---
> >>
> >> Changes in v2:
> >> - added TEGRA_UARTA_MICROSD Kconfig option
> >> - removed .dtsi for enabling UART over microSD
> >> - modified transformer DT to use UARTA and correct pinmux when
> >>    TEGRA_UARTA_MICROSD is enabled; it is enough to flip a single
> >>    switch to enable/disable UART over microSD
> >>
> >>   arch/arm/dts/tegra20-asus-transformer.dtsi | 24 ++++++++++++++++++++++
> >>   arch/arm/mach-tegra/tegra20/Kconfig        | 15 ++++++++++++++
> >>   2 files changed, 39 insertions(+)
> >>
> >> diff --git a/arch/arm/dts/tegra20-asus-transformer.dtsi b/arch/arm/dts/tegra20-asus-transformer.dtsi
> >> index 49efabbfd92..9ea323c81f3 100644
> >> --- a/arch/arm/dts/tegra20-asus-transformer.dtsi
> >> +++ b/arch/arm/dts/tegra20-asus-transformer.dtsi
> >> @@ -5,7 +5,13 @@
> >>
> >>   / {
> >>          chosen {
> >> +#if CONFIG_IS_ENABLED(TEGRA_ENABLE_UARTA)
> >> +               stdout-path = &uarta;
> >> +#elif CONFIG_IS_ENABLED(TEGRA_ENABLE_UARTD)
> >>                  stdout-path = &uartd;
> >> +#else
> >> +#error Unsupported UART
> >> +#endif
> >>          };
> >>
> >>          aliases {
> >> @@ -195,10 +201,17 @@
> >>                                  nvidia,function = "i2c1";
> >>                          };
> >>
> >> +#if CONFIG_IS_ENABLED(TEGRA_UARTA_SDB_SDD)
> >> +                       dbguart {
> >> +                               nvidia,pins = "sdb", "sdd";
> >> +                               nvidia,function = "uarta";
> >> +                       };
> >> +#else
> >>                          sdb {
> >>                                  nvidia,pins = "sdb", "sdc", "sdd", "slxc", "slxk";
> >>                                  nvidia,function = "sdio3";
> >>                          };
> >> +#endif
> >>
> >>                          sdio1 {
> >>                                  nvidia,pins = "sdio1";
> >> @@ -376,7 +389,13 @@
> >>                  };
> >>          };
> >>
> >> +#if CONFIG_IS_ENABLED(TEGRA_ENABLE_UARTA)
> >> +       uarta: serial@70006000 {
> >> +#elif CONFIG_IS_ENABLED(TEGRA_ENABLE_UARTD)
> >>          uartd: serial@70006300 {
> >> +#else
> >> +#error Unsupported UART
> >> +#endif
> >>                  status = "okay";
> >>                  clock-frequency = <216000000>;
> >>          };
> >> @@ -434,7 +453,12 @@
> >>          };
> >>
> >>          sdmmc3: sdhci@c8000400 {
> >> +#if CONFIG_IS_ENABLED(TEGRA_UARTA_MICROSD)
> >> +               /* Can't use both at the same time */
> >> +               status = "disabled";
> >> +#else
> >>                  status = "okay";
> >> +#endif
> >>                  bus-width = <4>;
> >>
> >>                  cd-gpios = <&gpio TEGRA_GPIO(I, 5) GPIO_ACTIVE_LOW>;
> >> diff --git a/arch/arm/mach-tegra/tegra20/Kconfig b/arch/arm/mach-tegra/tegra20/Kconfig
> >> index 3349f1e2786..c2c51660216 100644
> >> --- a/arch/arm/mach-tegra/tegra20/Kconfig
> >> +++ b/arch/arm/mach-tegra/tegra20/Kconfig
> >> @@ -77,6 +77,21 @@ endchoice
> >>   config SYS_SOC
> >>          default "tegra20"
> >>
> >> +config TEGRA_UARTA_MICROSD
> >> +       bool "UARTA on MicroSD breakout board"
> >> +       default n
> >> +       depends on TEGRA_ENABLE_UARTA && TARGET_TRANSFORMER_T20
> >> +       select TEGRA_UARTA_SDB_SDD
> >> +       help
> >> +         Repurpose the SD card slot for getting access to the UARTA serial
> >> +         console. Primarily useful only for low level u-boot debugging on
> >> +         tablets, where normal UARTD is difficult to access and requires
> >> +         device disassembly and/or soldering. Enabling this option causes
> >> +         UARTA TX to become exposed on SDD and RX on SDB pins which correspond
> >> +         to microSD CLK and CMD pins respectively. Currently this is supported
> >> +         only on Transformer T20, support for other platforms may require DT
> >> +         and configs (from include/configs/*) updates.
> >> +
> >>   source "board/nvidia/harmony/Kconfig"
> >>   source "board/avionic-design/medcom-wide/Kconfig"
> >>   source "board/compal/paz00/Kconfig"
> >> --
> >> 2.48.1
> >>
> > This is not applicable since this is a hack by nature, BUT if you
> > contain this in the transformer t20 board and Kconfig (no dts
> > changes), this may be applied.
> Ok, then I'll drop DTS changes. I will add few words about this option
> in Transformer documentation
> and a note in Kconfig help to not surprise users with not booting U-Boot
> as enabling this option without
> changing DTS causes U-Boot to hang.

You should remove then Kconfig option as well. Add a new chapter to
Transformer T20 documentation which describes this method, here[1] you
may find a similar approach but info is in the commit message of
tegra30 uart-e funcmux. Additionally, as I have said previously, these
changes can be contained in the transformer t20 board file by using
some device tree manipulations from there.

---
1 https://source.denx.de/u-boot/u-boot/-/commit/b515d7ae0de51a26f73b2ddb5ea4db0d95b67d7a

Re: [PATCH v2 3/3] tegra: allow to expose UART on microSD slot

[Artur Kowalski]

W dniu 01.04.2025 o 15:48, Svyatoslav Ryhel pisze:

> вт, 1 квіт. 2025 р. о 16:34 Artur Kowalski <arturkow2000@gmail.com> пише:
>>
>> W dniu 31.03.2025 o 07:51, Svyatoslav Ryhel pisze:
>>> нд, 30 бер. 2025 р. о 22:27 Artur Kowalski <arturkow2000@gmail.com> пише:
>>>> Tegra20 has mux allowing to repurpose microSD as UART on boards which
>>>> use sdmmc3 controller for microSD. Add TEGRA_UARTA_MICROSD to enable
>>>> this feature. It is currently supported on Transformer T20, support for
>>>> other boards may require Device Tree changes.
>>>>
>>>> Update Transformer T20 DTS to select correct pinmux and stdout-path
>>>> based on TEGRA_UARTA_MICROSD.
>>>>
>>>> Signed-off-by: Artur Kowalski <arturkow2000@gmail.com>
>>>> ---
>>>>
>>>> Changes in v2:
>>>> - added TEGRA_UARTA_MICROSD Kconfig option
>>>> - removed .dtsi for enabling UART over microSD
>>>> - modified transformer DT to use UARTA and correct pinmux when
>>>>     TEGRA_UARTA_MICROSD is enabled; it is enough to flip a single
>>>>     switch to enable/disable UART over microSD
>>>>
>>>>    arch/arm/dts/tegra20-asus-transformer.dtsi | 24 ++++++++++++++++++++++
>>>>    arch/arm/mach-tegra/tegra20/Kconfig        | 15 ++++++++++++++
>>>>    2 files changed, 39 insertions(+)
>>>>
>>>> diff --git a/arch/arm/dts/tegra20-asus-transformer.dtsi b/arch/arm/dts/tegra20-asus-transformer.dtsi
>>>> index 49efabbfd92..9ea323c81f3 100644
>>>> --- a/arch/arm/dts/tegra20-asus-transformer.dtsi
>>>> +++ b/arch/arm/dts/tegra20-asus-transformer.dtsi
>>>> @@ -5,7 +5,13 @@
>>>>
>>>>    / {
>>>>           chosen {
>>>> +#if CONFIG_IS_ENABLED(TEGRA_ENABLE_UARTA)
>>>> +               stdout-path = &uarta;
>>>> +#elif CONFIG_IS_ENABLED(TEGRA_ENABLE_UARTD)
>>>>                   stdout-path = &uartd;
>>>> +#else
>>>> +#error Unsupported UART
>>>> +#endif
>>>>           };
>>>>
>>>>           aliases {
>>>> @@ -195,10 +201,17 @@
>>>>                                   nvidia,function = "i2c1";
>>>>                           };
>>>>
>>>> +#if CONFIG_IS_ENABLED(TEGRA_UARTA_SDB_SDD)
>>>> +                       dbguart {
>>>> +                               nvidia,pins = "sdb", "sdd";
>>>> +                               nvidia,function = "uarta";
>>>> +                       };
>>>> +#else
>>>>                           sdb {
>>>>                                   nvidia,pins = "sdb", "sdc", "sdd", "slxc", "slxk";
>>>>                                   nvidia,function = "sdio3";
>>>>                           };
>>>> +#endif
>>>>
>>>>                           sdio1 {
>>>>                                   nvidia,pins = "sdio1";
>>>> @@ -376,7 +389,13 @@
>>>>                   };
>>>>           };
>>>>
>>>> +#if CONFIG_IS_ENABLED(TEGRA_ENABLE_UARTA)
>>>> +       uarta: serial@70006000 {
>>>> +#elif CONFIG_IS_ENABLED(TEGRA_ENABLE_UARTD)
>>>>           uartd: serial@70006300 {
>>>> +#else
>>>> +#error Unsupported UART
>>>> +#endif
>>>>                   status = "okay";
>>>>                   clock-frequency = <216000000>;
>>>>           };
>>>> @@ -434,7 +453,12 @@
>>>>           };
>>>>
>>>>           sdmmc3: sdhci@c8000400 {
>>>> +#if CONFIG_IS_ENABLED(TEGRA_UARTA_MICROSD)
>>>> +               /* Can't use both at the same time */
>>>> +               status = "disabled";
>>>> +#else
>>>>                   status = "okay";
>>>> +#endif
>>>>                   bus-width = <4>;
>>>>
>>>>                   cd-gpios = <&gpio TEGRA_GPIO(I, 5) GPIO_ACTIVE_LOW>;
>>>> diff --git a/arch/arm/mach-tegra/tegra20/Kconfig b/arch/arm/mach-tegra/tegra20/Kconfig
>>>> index 3349f1e2786..c2c51660216 100644
>>>> --- a/arch/arm/mach-tegra/tegra20/Kconfig
>>>> +++ b/arch/arm/mach-tegra/tegra20/Kconfig
>>>> @@ -77,6 +77,21 @@ endchoice
>>>>    config SYS_SOC
>>>>           default "tegra20"
>>>>
>>>> +config TEGRA_UARTA_MICROSD
>>>> +       bool "UARTA on MicroSD breakout board"
>>>> +       default n
>>>> +       depends on TEGRA_ENABLE_UARTA && TARGET_TRANSFORMER_T20
>>>> +       select TEGRA_UARTA_SDB_SDD
>>>> +       help
>>>> +         Repurpose the SD card slot for getting access to the UARTA serial
>>>> +         console. Primarily useful only for low level u-boot debugging on
>>>> +         tablets, where normal UARTD is difficult to access and requires
>>>> +         device disassembly and/or soldering. Enabling this option causes
>>>> +         UARTA TX to become exposed on SDD and RX on SDB pins which correspond
>>>> +         to microSD CLK and CMD pins respectively. Currently this is supported
>>>> +         only on Transformer T20, support for other platforms may require DT
>>>> +         and configs (from include/configs/*) updates.
>>>> +
>>>>    source "board/nvidia/harmony/Kconfig"
>>>>    source "board/avionic-design/medcom-wide/Kconfig"
>>>>    source "board/compal/paz00/Kconfig"
>>>> --
>>>> 2.48.1
>>>>
>>> This is not applicable since this is a hack by nature, BUT if you
>>> contain this in the transformer t20 board and Kconfig (no dts
>>> changes), this may be applied.
>> Ok, then I'll drop DTS changes. I will add few words about this option
>> in Transformer documentation
>> and a note in Kconfig help to not surprise users with not booting U-Boot
>> as enabling this option without
>> changing DTS causes U-Boot to hang.
> You should remove then Kconfig option as well. Add a new chapter to
> Transformer T20 documentation which describes this method, here[1] you
> may find a similar approach but info is in the commit message of
> tegra30 uart-e funcmux. Additionally, as I have said previously, these
> changes can be contained in the transformer t20 board file by using
> some device tree manipulations from there.

Currently I'm working on few other things both in U-Boot in OS, some of 
patches probably I will send to upstream
in the coming weeks, but eventually, I will come back to this.

> ---
> 1 https://source.denx.de/u-boot/u-boot/-/commit/b515d7ae0de51a26f73b2ddb5ea4db0d95b67d7a