Re: [PATCH v1 1/1] Platform/RaspberryPi/ConfigDxe: Fix JTAG Pinout for Pi3/4

["Andrei Warkentin" <awarkentin@vmware.com>]

[-- Attachment #1: Type: text/plain, Size: 3501 bytes --]

Hi folks,

No objection at all. IIRC the original pin selection was driven by an article I read about using OpenOCD with Pi 3.

A
________________________________
From: Pete Batard <pete@akeo.ie>
Sent: Tuesday, September 15, 2020 7:26 AM
To: Jeff Booher-Kaeding <jeff.booher-kaeding@arm.com>; devel@edk2.groups.io <devel@edk2.groups.io>
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>; Leif Lindholm <leif@nuviainc.com>; Andrei Warkentin <awarkentin@vmware.com>
Subject: Re: [PATCH v1 1/1] Platform/RaspberryPi/ConfigDxe: Fix JTAG Pinout for Pi3/4

Copying Andrei on this, as the existing JTAG pinout is not technically
incorrect, since GPIO pin 4 can be used for TDI in ALT5 mode, and we are
using the relevant ALT mode in the existing code. See
https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fsysprogs.com%2FVisualKernel%2Ftutorials%2Fraspberry%2Fjtagsetup%2F&amp;data=02%7C01%7Cawarkentin%40vmware.com%7C1c1badf5e6f1433b44b508d859728a32%7Cb39138ca3cee4b4aa4d6cd83d9dd62f0%7C0%7C0%7C637357695767996220&amp;sdata=rGIzM4Io36gFJrAK%2F4xZs0fm0DpXVvamhOYYXfc09ek%3D&amp;reserved=0

As far as I'm concerned, I think it makes sense to use the same ALT mode
and have all the JTAG pins grouped, but I'd like to confirm whether we
deliberately chose not to use GPIO 26 in order to leave it available for
some other purpose, before I approve this patch.

If Andrei says he's okay with it, then I see no objection to this change.

Regards,

/Pete

On 2020.09.14 22:32, Jeff Booher-Kaeding wrote:
> Updated the pinout to match the Pi4 datasheet, tested with the RPi4, Pi3 Datasheet has same pinout.
>
> Signed-off-by: Jeff Booher-Kaeding <Jeff.booher-kaeding@arm.com>
>
> Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
> Cc: Leif Lindholm <leif@nuviainc.com>
> Cc: Pete Batard <pete@akeo.ie>
> ---
>   Platform/RaspberryPi/Drivers/ConfigDxe/ConfigDxe.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/Platform/RaspberryPi/Drivers/ConfigDxe/ConfigDxe.c b/Platform/RaspberryPi/Drivers/ConfigDxe/ConfigDxe.c
> index ac1004fe1836..6e793efb8227 100644
> --- a/Platform/RaspberryPi/Drivers/ConfigDxe/ConfigDxe.c
> +++ b/Platform/RaspberryPi/Drivers/ConfigDxe/ConfigDxe.c
> @@ -502,7 +502,7 @@ ApplyVariables (
>      * 1           VREF        N/A               1
>
>      * 3           nTRST       GPIO22    ALT4    15
>
>      * 4           GND         N/A               9
>
> -   * 5           TDI         GPIO4     ALT5    7
>
> +   * 5           TDI         GPIO26    ALT4    37
>
>      * 7           TMS         GPIO27    ALT4    13
>
>      * 9           TCK         GPIO25    ALT4    22
>
>      * 11          RTCK        GPIO23    ALT4    16
>
> @@ -510,14 +510,14 @@ ApplyVariables (
>      */
>
>     if (PcdGet32 (PcdDebugEnableJTAG)) {
>
>       GpioPinFuncSet (22, GPIO_FSEL_ALT4);
>
> -    GpioPinFuncSet (4, GPIO_FSEL_ALT5);
>
> +    GpioPinFuncSet (26, GPIO_FSEL_ALT4);
>
>       GpioPinFuncSet (27, GPIO_FSEL_ALT4);
>
>       GpioPinFuncSet (25, GPIO_FSEL_ALT4);
>
>       GpioPinFuncSet (23, GPIO_FSEL_ALT4);
>
>       GpioPinFuncSet (24, GPIO_FSEL_ALT4);
>
>     } else {
>
>       GpioPinFuncSet (22, GPIO_FSEL_INPUT);
>
> -    GpioPinFuncSet (4, GPIO_FSEL_INPUT);
>
> +    GpioPinFuncSet (26, GPIO_FSEL_INPUT);
>
>       GpioPinFuncSet (27, GPIO_FSEL_INPUT);
>
>       GpioPinFuncSet (25, GPIO_FSEL_INPUT);
>
>       GpioPinFuncSet (23, GPIO_FSEL_INPUT);
>


[-- Attachment #2: Type: text/html, Size: 7230 bytes --]