On Mon, 9 Mar 2020 at 20:31, Michael Walle <michael@xxxxxxxx> wrote: > > Am 2020-03-09 19:14, schrieb Vladimir Oltean: > > On Mon, 9 Mar 2020 at 20:03, Michael Walle <michael@xxxxxxxx> wrote: > >> Am 2020-03-09 15:56, schrieb Vladimir Oltean: > >> > From: Vladimir Oltean <vladimir.oltean@xxxxxxx> > >> > > >> > This series addresses a few issues that were missed during the previous > >> > series "[PATCH 00/12] TCFQ to XSPI migration for NXP DSPI driver", on > >> > SoCs other than LS1021A and LS1043A. DMA mode has been completely > >> > broken > >> > by that series, and XSPI mode never worked on little-endian > >> > controllers. > >> > > >> > Then it introduces support for the LS1028A chip, whose compatible has > >> > recently been documented here: > >> > > >> > https://lore.kernel.org/linux-devicetree/20200218171418.18297-1-michael@xxxxxxxx/ > >> > >> If it is not compatible with the LS1021A the second compatible string > >> should be removed. Depending on the other remark about the endianess, > >> it might still be compatible, though. > >> > > > > Please feel free to remove it. I wasn't actually planning to add it in > > the first place, but now it that it's there it doesn't really bother > > anybody either. > > But it won't work if the endianess depends on the compatible string ;) > True. > >> > >> > The device tree for the LS1028A SoC is extended with DMA channels > >> > definition, such that even though the default operating mode is XSPI, > >> > one can simply change DSPI_XSPI_MODE to DSPI_DMA_MODE in the > >> > devtype_data structure of the driver and use that instead. > >> > >> wouldn't it make more sense, to use DMA is the dma node is present > >> in the device tree? otherwise use XSPI mode? I don't think it is > >> really handy to change the mode inside the driver. > >> > > > > Let's keep it simple. The driver should configure the hardware in the > > most efficient and least buggy mode available. Right now that is XSPI. > > The hardware description (aka the device tree) is a separate topic. If > > there ever arises any situation where there are corner cases with XSPI > > mode, it's good to have a fallback in the form of DMA mode, and not > > have to worry about yet another problem (which is that there are 2 > > sets of device tree blobs in deployment). > > Point taken. But this is not how other drivers behave, which uses the > DMA if its given in the device node. > Also true. > Btw. do other SoCs perform better with DMA? > Not that I know of. My general rule of thumb for this controller is: if it supports XSPI then use that, otherwise use DMA. Luckily there is just one controller that supports none of those, and that would be Coldfire, which uses the braindead EOQ mode. I don't have the hardware to do testing on that, but in principle if I did, I would have converted that as well to the more functional but less efficient TCFQ mode (now removed). > -michael > > > TL;DR: These DMA channels don't really bother anybody but you never > > know when they might come in handy. > > > >> -michael > >> > >> > > >> > For testing, benchmarking and debugging, the mikroBUS connector on the > >> > LS1028A-RDB is made available via spidev. > >> > > >> > Vladimir Oltean (6): > >> > spi: spi-fsl-dspi: Don't access reserved fields in SPI_MCR > >> > spi: spi-fsl-dspi: Fix little endian access to PUSHR CMD and TXDATA > >> > spi: spi-fsl-dspi: Fix oper_word_size of zero for DMA mode > >> > spi: spi-fsl-dspi: Add support for LS1028A > >> > arm64: dts: ls1028a: Specify the DMA channels for the DSPI > >> > controllers > >> > arm64: dts: ls1028a-rdb: Add a spidev node for the mikroBUS > >> > > >> > .../boot/dts/freescale/fsl-ls1028a-rdb.dts | 14 +++++ > >> > .../arm64/boot/dts/freescale/fsl-ls1028a.dtsi | 6 +++ > >> > drivers/spi/spi-fsl-dspi.c | 54 +++++++++++++++---- > >> > 3 files changed, 64 insertions(+), 10 deletions(-) > > > > Thanks, > > -Vladimir -Vladimir
