Re: [PATCH 03/15] dmaengine: dw: rename masters to reflect actual topology

["Måns Rullgård" <mans@mansr.com>]

Hans-Christian Noren Egtvedt <egtvedt@samfundet.no> writes:

> Around Sun 24 Jan 2016 20:19:46 +0000 or thereabout, Måns Rullgård wrote:
>> Hans-Christian Noren Egtvedt <egtvedt@samfundet.no> writes:
>>> Around Sun 24 Jan 2016 19:21:50 +0000 or thereabout, Mans Rullgard wrote:
>>>> From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
>>>> 
>>>> The source and destination masters are reflecting buses or their layers to
>>>> where the different devices can be connected. The patch changes the master
>>>> names to reflect which one is related to which independently on the transfer
>>>> direction.
>>>> 
>>>> The outcome of the change is that the memory data width is now always limited
>>>> by a data width of the master which is dedicated to communicate to memory.
>>>> 
>>>> The patch will not break anything since all current users have the same data
>>>> width for all masters. Though it would be nice to revisit avr32 plaforms to
>>>> check what is the actual hardware topology is used there. It seems that it has
>>>> one bus and two masters on it as stated by Table 8-2, that's why everything
>>>> works independently on the master in use. The purpose of the sequential patch
>>>> is to fix the driver for configuration of more that one bus.
>>>
>>> Not entirely sure what you want to have confirmed here. There are multiple
>>> masters and slaves on the HMATRIX internal bus on AVR32, and the DMA
>>> controller supports up to three simultaneous configurations.
>>>
>>> Sounds good to support configuration of more than one bus. I thought we
>>> always did support that? Perhaps it was a non-standard avr32 implementation.
>> 
>> The DW DMA controller on the AT32AP7000 serves the MCI, AC97, and ABDAC
>> peripherals.  It appears to work regardless of the values put in the
>> various master select fields.  Perhaps the topology is hardwired in the
>> DMA controller and those fields are ignored.  The AVR32 works both
>> before and after this patch series, the main purpose of which (at least
>> my patches) is to fix the SATA driver on 460EX.
>
> DEST_PER and SRC_PER in the DMA controller selects this, numbers placed here
> should match the table you most likely found, 9-3.
>
> Wiring the handshake connections is done with the struct dw_dma_slave src_id
> or dst_id member, depending on data direction. Configured in the at32ap700x.c
> machine code.
>
> It is not hard wired on avr32, as there are not one-to-one configurations and
> masters.

This is about the SMS (Source Master Select) and DMS (Destination Master
Select) fields in the CTLxL register and the LMS (List Master Select)
field in the LLPx register.

>>>> The change is done in the assumption that src_master and dst_master are
>>>> reflecting a connection to the memory and peripheral correspondently on all
>>>> platforms except 460ex.
>
> OK, I have no knowledge about the 460ex.
>
>>>> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
>>>> Signed-off-by: Mans Rullgard <mans@mansr.com>
>>>
>>> For the avr32 related stuff:
>>>
>>> Acked-by: Hans-Christian Egtvedt <egtvedt@samfundet.no>
>>>
>>>> ---
>>>>  Documentation/devicetree/bindings/dma/snps-dma.txt |  4 ++--
>>>>  arch/avr32/mach-at32ap/at32ap700x.c                | 16 ++++++++--------
>>>>  drivers/ata/sata_dwc_460ex.c                       |  4 ++--
>>>>  drivers/dma/dw/core.c                              | 15 +++++++--------
>>>>  drivers/dma/dw/platform.c                          | 12 ++++++------
>>>>  drivers/dma/dw/regs.h                              |  4 ++--
>>>>  drivers/spi/spi-pxa2xx-pci.c                       |  8 ++++----
>>>>  drivers/tty/serial/8250/8250_pci.c                 |  8 ++++----
>>>>  include/linux/platform_data/dma-dw.h               |  8 ++++----
>>>>  9 files changed, 39 insertions(+), 40 deletions(-)
>>>
>>> <snipp diff>
> -- 
> Best regards, Hans-Christian Egtvedt

-- 
Måns Rullgård