On 20/01/15 14:26, Graeme Gregory wrote: > On Tue, Jan 20, 2015 at 01:55:01PM +0000, Andre Przywara wrote: >> Hi Graeme, >> >> On 20/01/15 13:08, Graeme Gregory wrote: >>> On Fri, Jan 16, 2015 at 05:22:56PM +0000, Andre Przywara wrote: >>>> 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. Cheers, Andre. -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
