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. Graeme -- 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
