On Thu, Feb 07, 2019 at 09:00:44PM +0000, Trent Piepho wrote: > On Mon, 2019-01-07 at 14:22 +0100, Stefan Agner wrote: > > Allow to use DMA for SPI by adding the appropriate DMA properites > > to the ecspi nodes. > > > > Signed-off-by: Stefan Agner <stefan@xxxxxxxx> > > --- > > arch/arm/boot/dts/imx7s.dtsi | 8 ++++++++ > > 1 file changed, 8 insertions(+) > > > > diff --git a/arch/arm/boot/dts/imx7s.dtsi b/arch/arm/boot/dts/imx7s.dtsi > > index a052198f6e96..b9330176c3af 100644 > > --- a/arch/arm/boot/dts/imx7s.dtsi > > +++ b/arch/arm/boot/dts/imx7s.dtsi > > @@ -653,6 +653,8 @@ > > clocks = <&clks IMX7D_ECSPI4_ROOT_CLK>, > > <&clks IMX7D_ECSPI4_ROOT_CLK>; > > clock-names = "ipg", "per"; > > + dmas = <&sdma 6 7 1>, <&sdma 7 7 2>; > > + dma-names = "rx", "tx"; > > status = "disabled"; > > }; > > After updating my kernel to linux-next on my IMX7d based device, I > found that an FPGA, which is programmed via the ECSPI interface, was no > longer accepting its image. > > I tracked the problem to this change. If I turn off DMA, it works. > > There's an interesting thing that happens when DMA is used. The SPI > clock changes. Instead of cycling continuously for the entire > transfer, it instead clocks out 8 bits, then pauses for 4 bit times, > then the next byte, etc. So it's a net of about 50% slower. The pause > between bytes scales with spi frequency to always be about 4 bits. > > Here's a trace with DMA: https://imagebin.ca/v/4WEkEnvsVSkq > > Here's what it looks like without DMA: > https://imagebin.ca/v/4WEkVfEqpQ12 > > It seems like there are other problems with DMA too. Here's an error > I'll random get every so often. > > [ 142.082325] spi_master spi1: I/O Error in DMA RX > [ 142.085678] spidev spi1.0: SPI transfer failed: -110 > [ 142.089389] spi_master spi1: failed to transfer one message from queue > > Not sure if the timeout is overly aggressive or if there is some other failure. > > Then sometimes there errors are worse: > > Internal error: Oops - undefined instruction: 0 [#1] PREEMPT SMP ARM > Modules linked in: > CPU: 0 PID: 1006 Comm: fpga-loader Not tainted 5.0.0-rc4-next-20190201 #1 > Hardware name: Freescale i.MX7 Dual (Device Tree) > PC is at sg_last+0x4c/0x68 > LR is at (null) > pc : [<80494800>] lr : [<00000000>] psr: 60010013 > sp : bf0add5c ip : bea94598 fp : bf371218 > r10: bf0949f0 r9 : 00000000 r8 : bf094800 > r7 : bdc39300 r6 : bf371000 r5 : bdc39300 r4 : bf094b68 > r3 : 00000000 r2 : 00000001 r1 : 00000001 r0 : bea94580 > Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user > Control: 30c5387d Table: bea94000 DAC: fffffffd > Process fpga-loader (pid: 1006, stack limit = 0x61bc8b73) > Stack: (0xbf0add5c to 0xbf0ae000) > dd40: 8056cdb0 > dd60: 8056c9ac 00001000 00000000 bdc39300 bf094800 bf094b68 bf371000 00000000 > dd80: bf0949f0 8056bc00 bf094800 bdc39300 bf0adeac bf094800 bf094ad0 80569edc > ... > dfc0: 00217301 00150000 00001000 00000036 00df2010 00000003 00001000 00df1008 > dfe0: 00022f70 7e9ebb14 000113b8 76f2a7f8 20010030 00000003 00000000 00000000 > [<80494800>] (sg_last) from [<8056cdb0>] (spi_imx_transfer+0xd8/0x448) > [<8056cdb0>] (spi_imx_transfer) from [<8056bc00>] (spi_bitbang_transfer_one+0x50/0xa0) > [<8056bc00>] (spi_bitbang_transfer_one) from [<80569edc>] (spi_transfer_one_message+0x18c/0x3e0) > [<80569edc>] (spi_transfer_one_message) from [<8056a498>] (__spi_pump_messages+0x368/0x518) > [<8056a498>] (__spi_pump_messages) from [<8056a7ec>] (__spi_sync+0x198/0x1a0) > [<8056a7ec>] (__spi_sync) from [<8056a818>] (spi_sync+0x24/0x3c) > [<8056a818>] (spi_sync) from [<8056ae14>] (spidev_sync+0x38/0x4c) > [<8056ae14>] (spidev_sync) from [<8056b6f4>] (spidev_ioctl+0x660/0x704) > [<8056b6f4>] (spidev_ioctl) from [<80335f9c>] (do_vfs_ioctl+0xac/0x79c) > [<80335f9c>] (do_vfs_ioctl) from [<803366c0>] (ksys_ioctl+0x34/0x58) > [<803366c0>] (ksys_ioctl) from [<80201120>] (ret_fast_syscall+0x0/0x4c) > Exception stack(0xbf0adfa8 to 0xbf0adff0) > dfa0: 00217301 00150000 00000003 40206b00 7e9ebb80 03938700 > dfc0: 00217301 00150000 00001000 00000036 00df2010 00000003 00001000 00df1008 > dfe0: 00022f70 7e9ebb14 000113b8 76f2a7f8 > Code: e1510002 1afffff3 e3530000 149df004 (e7f001f2) > ---[ end trace 1588229fc7541669 ]--- > > I think DMA on imx not be ready for prime time yet. I dropped both patches from my tree. Shawn
