[PATCH 0/4] New UART drivers for PL011 and Mini UART

[Utkarsh Verma]

A gentle reminder for this patch. Please have a look at this and let me
know what changes are required. Once this is merged, I have a few more
patches building upon this.

Regards,
Utkarsh

On Wed, Aug 30, 2023 at 9:47 AM Utkarsh Verma <utkarsh at bitbanged.com> wrote:

> This patch series adds two drivers, PL011 and Mini UART. Both support
> interrupts and implement the termios API.
>
> Why add a new driver for the PL011 when we already have one?
>
> The existing driver is a very basic one and uses memory-mapped structs
> to access the registers. This proved to be problematic for the
> 'aarch64/raspberrypi4b' BSP as the RPi 4B's MMU does not reserve the
> entirety of the space required by the PL011 register struct.
>
> Even the existing driver doesn't use all the struct members. So, in the
> new driver, macros were used instead. This has the benefit of minimalism
> and ensures that we only add tested features to the driver.
>
> This driver builds upon the PL011 driver present in the Xilinx Versal
> BSP and addresses the IRQ startup hack.
>
> In short, the new PL011 driver has the features provided by the
> existing driver, and it meshes well with the termios API.
>
> Lastly, there's one thing I need feedback on. The PL011 has a hardware
> limitation which requires me to invoke the IRQ handler manually, the
> first time. For this, I need access to the `tty` struct in the
> `write_buffer` function.
>
>
> https://github.com/UtkarshVerma/rtems/blob/uart-drivers/bsps/shared/dev/serial/pl011.c#L301
>
> For now, I store the tty in the device context and then pass the context
> to the IRQ handler. Is this a good approach? Are there better ways to do
> this?
>
> For convenience, feel free to check out my GitHub fork which has these
> changes:
>
> https://github.com/UtkarshVerma/rtems/tree/uart-drivers
>
> Utkarsh Verma (4):
>   bsps/shared: Add new PL011 driver with IRQ support
>   bsps/shared: Add new Mini UART driver
>   spec: Add Mini UART and PL011 drivers to build spec
>   bsps: Update BSPs to use the new PL011 driver
>
>  bsps/aarch64/a53/console/console.c            |  15 +-
>  bsps/aarch64/a72/console/console.c            |  15 +-
>  bsps/aarch64/raspberrypi/console/console.c    |  29 +-
>  bsps/arm/raspberrypi/console/console-config.c |  27 +-
>  .../realview-pbx-a9/console/console-polled.c  |   5 +-
>  .../arm/realview-pbx-a9/include/bsp/console.h |   4 +-
>  bsps/arm/xen/console/console.c                |  15 +-
>  bsps/include/dev/serial/arm-pl011-regs.h      | 143 ------
>  .../dev/serial/{arm-pl011.h => mini-uart.h}   |  52 +-
>  bsps/include/dev/serial/pl011.h               |  68 +++
>  bsps/shared/dev/serial/arm-pl011.c            | 104 ----
>  bsps/shared/dev/serial/mini-uart.c            | 316 ++++++++++++
>  bsps/shared/dev/serial/pl011.c                | 470 ++++++++++++++++++
>  .../aarch64/raspberrypi/bspraspberrypi4.yml   |   1 -
>  spec/build/bsps/obj.yml                       |   7 +-
>  15 files changed, 934 insertions(+), 337 deletions(-)
>  delete mode 100644 bsps/include/dev/serial/arm-pl011-regs.h
>  rename bsps/include/dev/serial/{arm-pl011.h => mini-uart.h} (64%)
>  create mode 100644 bsps/include/dev/serial/pl011.h
>  delete mode 100644 bsps/shared/dev/serial/arm-pl011.c
>  create mode 100644 bsps/shared/dev/serial/mini-uart.c
>  create mode 100644 bsps/shared/dev/serial/pl011.c
>
> --
> 2.41.0
>
>
>
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