[PATCH 1/1] zynq-uart: Fix set_attributes implementation

Joel Sherrill joel at rtems.org
Tue Feb 9 23:21:03 UTC 2021

On Tue, Feb 9, 2021 at 5:08 PM Chris Johns <chrisj at rtems.org> wrote:

> On 9/2/21 11:42 pm, Jan Sommer wrote:
> > From: Kinsey Moore <kinsey.moore at oarcorp.com>
> >
> > The zynq-uart set_attributes implementation was configured to always
> > return false which causes spconsole01 to fail. This restores the
> > disabled implementation which sets the baud rate registers
> > appropriately and allows spconsole01 to pass. This also expands the
> > set_attributes functionality to allow setting of the stop bits,
> > character width, and parity.
> Hmmm I missed this change.
> Sebastian changed the Zynq driver to return an error. Returning an error is
> correct because the attributes are not being set however we have a couple
> of
> design approaches clashing.
> The issue pulls right back to the Xilinx SystemZ design dialogue box. The
> hardware designer has the ability to set the serial port defaults. These
> settings form part of the ps7init data the FSBL paints into the hardware
> very
> early in the boot process. Also in this data are parallel port pin
> settings, AXI
> clocks, memory and more so lots of important stuff. The Xilinx bootloader
> and
> ones I have created (I do not know about uboot) do not touch the UART
> hardware
> on purpose so the system designer has control. Then in 2017 Sebastian
> pushed a
> change to force the baudrate to a BSP specific default.
> This is normally all OK because all Zynq designs I know of use the default
> of
> 115200,8,n,1 for the configuration. A problem arises when these defaults
> are varied.
> Maybe something explaining this in the user manual ...
> https://docs.rtems.org/branches/master/user/bsps/bsps-arm.html#xilinx-zynq
> so we have provided information on what to change?

I wonder if there should be a configuration parameter for the default
At least "don't override the defaults"

> The other approach is not to touch the defaults in hardware and allow a get
> attributes to discover them? Does termios drivers have a low level get? I
> can
> see a set but no get in the zynq uart driver.

No. This reflects termios from the POSIX perspective.


> Chris
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