rp1-pio+dw-axi-dmac: add cyclic DMA support, ability to select light vs heavy DMA - #7598
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The cyclic DMA implementation of the dw-axi-dmac driver was broken: it actually stopped the DMA at the end of each period and had to be restarted by the interrupt handler. That can cause data loss. The root cause is the use of the CH_CTL_H_LLI_LAST flag in the last period DMA descriptor: this stops the DMA and triggers an irq. But for cyclic DMA you just want to get an interrupt and not stop the DMA. For that use the CH_CTL_H_LLI_BLKTRF: that just raises an interrupt but does not stop the DMA. In the interrupt handler we need to mark all the used descriptors from the last period as valid again: the DMA HW clears the CH_CTL_H_LLI_VALID bit after retiring that descriptor, and so it has to be set again or the DMA would stop. With these changes the cyclic DMA works as it should. In addition, when the current dw_axi_dma_chan_prep_cyclic implementation is given a span larger than the maximum supported by the DMAC it attempts to divide it into a number of roughly equal-sized segments. This requires care that the results are all multiples of the transfer unit, e.g. words for transfers with a hardware register. Simplify the logic by making all segments as large as possible except for the last one. Signed-off-by: Hans Verkuil <hverkuil@kernel.org>
We want to be able to select 'light' DMAs (25 MB/s), so add eight more entries without the DMA_FLAG_HEAVY flag and name them with the 'l' suffix for 'light'. Signed-off-by: Hans Verkuil <hverkuil@kernel.org>
Add a new ioctl to be able to pass flags to the driver. This new flags field can be used to select 'heavy' (50 MB/s) and 'light' (25 MB/s) DMA engines. The existing PIO_IOC_SM_CONFIG_XFER(32) ioctls keep their current behavior of preferring to use the 'heavy' DMA engine and fall back to the 'light' variant. Signed-off-by: Hans Verkuil <hverkuil@kernel.org>
If the DMA is freed first, and the SMs are disabled afterwards, then the next time you use the DMA the first 4-8 words are corrupt (old data). Disable the SMs first, then free the DMA. With this change there is no longer old data seen in the next run. Signed-off-by: Hans Verkuil <hverkuil@kernel.org>
Add a new RP1_PIO_SM_CONFIG_XFER_FL_DMA_CYCLE flag to select cyclic DMA. In that case buf_size is the size of a single cycle and there are buf_count cycles. So the total buffer size will be buf_size * buf_count. Signed-off-by: Hans Verkuil <hverkuil@kernel.org>
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It looks great - I can't think of a reason not to merge as-is. |
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kernel: staging: vc04_services: fix pointer arithmetic in create_pagelist See: raspberrypi/linux#7593 kernel: rp1-pio+dw-axi-dmac: add cyclic DMA support, ability to select light vs heavy DMA See: raspberrypi/linux#7598 kernel: overlays: ed-backlight-pwm: Add EDATEC PWM backlight overlay See: raspberrypi/linux#7597 kernel: configs: Add CAN_VXCAN=m See: raspberrypi/linux#7592 kernel: media/hevc_d: Improve checking and cleanup of decoder See: raspberrypi/linux#7583 kernel: drm/vc4: hdmi: Don't write past the end of a packet RAM slot See: raspberrypi/linux#7579 kernel: bcm2835-i2s: fail capture open cleanly when FIFO clear has no clock See: raspberrypi/linux#7586 kernel: vc04_services: bounds and fd handling fixes See: raspberrypi/linux#7576 kernel: overlays: wm8960-soundcard: Add media parameter See: raspberrypi/linux#7577 kernel: overlays: rt5616: Add RT5616 audio codec overlay See: raspberrypi/linux#7574 kernel: arm64: defconfig: Enable RT5616 codec in Pi configurations See: raspberrypi/linux#7575
popcornmix
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kernel: staging: vc04_services: fix pointer arithmetic in create_pagelist See: raspberrypi/linux#7593 kernel: rp1-pio+dw-axi-dmac: add cyclic DMA support, ability to select light vs heavy DMA See: raspberrypi/linux#7598 kernel: overlays: ed-backlight-pwm: Add EDATEC PWM backlight overlay See: raspberrypi/linux#7597 kernel: configs: Add CAN_VXCAN=m See: raspberrypi/linux#7592 kernel: media/hevc_d: Improve checking and cleanup of decoder See: raspberrypi/linux#7583 kernel: drm/vc4: hdmi: Don't write past the end of a packet RAM slot See: raspberrypi/linux#7579 kernel: bcm2835-i2s: fail capture open cleanly when FIFO clear has no clock See: raspberrypi/linux#7586 kernel: vc04_services: bounds and fd handling fixes See: raspberrypi/linux#7576 kernel: overlays: wm8960-soundcard: Add media parameter See: raspberrypi/linux#7577 kernel: overlays: rt5616: Add RT5616 audio codec overlay See: raspberrypi/linux#7574 kernel: arm64: defconfig: Enable RT5616 codec in Pi configurations See: raspberrypi/linux#7575
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This PR adds support for cyclic DMA for FROM_SM and the ability to select a 'heavy' or 'light' DMA engine. This required adding a new PIO_IOC_SM_CONFIG_XFER_V2 ioctl with a new flags field.
It also adds a fix where old corrupt data would be DMAed when you do a second DMA run.
With these changes it is possible to sample up to 6 pins at full speed (200 MHz) from the PIO using 4 SMs and both 'heavy' DMAs and two 'light' DMAs for a total of about 150 MB/s.