On Tue, Jan 20, 2015 at 02:52:21PM +0000, Graeme Gregory wrote:

On Tue, Jan 20, 2015 at 02:33:00PM +0000, Andre Przywara wrote:

quoted

On 20/01/15 14:26, Graeme Gregory wrote:

quoted

On Tue, Jan 20, 2015 at 01:55:01PM +0000, Andre Przywara wrote:

quoted

Hi Graeme,

On 20/01/15 13:08, Graeme Gregory wrote:

quoted

On Fri, Jan 16, 2015 at 05:22:56PM +0000, Andre Przywara wrote:

quoted

The ARM Server Base System Architecture[1] document describes a
generic UART which is a subset of the PL011 UART.
It lacks DMA support, baud rate control and modem status line
control, among other things.
The idea is to move the UART initialization and setup into the
firmware (which does this job today already) and let the kernel just
use the UART for sending and receiving characters.

This patchset integrates support for this UART subset into the
existing PL011 driver - basically by refactoring some
functions and providing a new uart_ops structure for it. It also has
a separate probe function to be not dependent on AMBA/PrimeCell.
It provides a device tree binding, but can easily be adapted to other
device configuration systems.
Beside the obvious effect of code sharing reusing most of the PL011
code has the advantage of not introducing another serial device
prefix, so it can go with ttyAMA, which seems to be pretty common.

This series relies on Dave's recent PL011 fix[2], which gets rid of
the loopback trick to get the UART going. There is a repo at [3]
(branch sbsa-uart/v1), which has this patch already integrated.

Patch 1/10 contains a bug fix which applies to the PL011 part also,
it should be considered regardless of the rest of the series.
Patch 2-7 refactor some PL011 functions by splitting them up into
smaller pieces, so that most of the code can be reused later by the
SBSA part.
Patch 8 and 9 introduce two new properties for the vendor structure,
this is for SBSA functionality which cannot be controlled by
separate uart_ops members only.
Patch 10 then finally drops in the SBSA specific code, by providing
a new uart_ops, vendor struct and probe function for it. Also the new
device tree binding is documented.

For testing you should be able to take any hardware which has a PL011
and change the DT to use a "arm,sbsa-uart" compatible string.
Of course testing with a real SBSA Generic UART is welcomed!

I have tested this series on Juno where it seems to work and also on FVP
model where there are some issues.

On the FVP when we enter usespace a couple of 32 character strings are
printed then nothing else. 32 Characters is a suspicious number.

Can you try to add:
-C bp.pl011_uart0.untimed_fifos=0
to your model command line? (given that your model supports this option)

We discovered that lately, also not sure how the default for this
setting is handled these days in the various model versions.

We are about to investigate this here atm.
This issue seems to be introduced by Dave's FIFO patch.

With this setting userspace functions better but loses characters
fairly regularly.

Are you using arm,sbsa-uart in the DT, but a default PL011 in the model
config? In my model the default PL011 version has a 16 byte FIFO only,
specifying:
-C bp.pl011_uart0.revision="r1p5"
upgrades this to the SBSA specified 32 byte FIFO size.
With this setting I don't see any character loses.

Yes with this setting all works with untimed_fifos=0

I was not aware of the differences in versions thanks.

Now I know how to correctly configure model I have now tested on FVP and
Juno so feel free to add my Tested-by:

Graeme