On 7/1/25 2:23 AM, Lothar Rubusch wrote: > On Sat, Jun 28, 2025 at 7:16 PM Jonathan Cameron <jic23@xxxxxxxxxx> wrote: >> >> On Sun, 22 Jun 2025 12:29:32 +0000 >> Lothar Rubusch <l.rubusch@xxxxxxxxx> wrote: >> >>> Cover the following tasks: >>> - Add scan_mask and scan_index to the IIO channel configuration. The >>> scan_index sets up buffer usage. According to the datasheet, the ADXL313 >>> uses a 13-bit wide data field in full-resolution mode. Set the >>> signedness, number of storage bits, and endianness accordingly. >>> >>> - Parse the devicetree for an optional interrupt line and configure the >>> interrupt mapping based on its presence. If no interrupt line is >>> specified, keep the FIFO in bypass mode as currently implemented. >>> >>> - Set up the interrupt handler. Add register access to detect and >>> evaluate interrupts. Implement functions to clear status registers and >>> reset the FIFO. >>> >>> - Implement FIFO watermark configuration and handling. Allow the >>> watermark level to be set, evaluate the corresponding interrupt, read >>> the FIFO contents, and push the data to the IIO channel. >>> >>> Signed-off-by: Lothar Rubusch <l.rubusch@xxxxxxxxx> >> Hi Lothar, >> > > Hi Jonathan, there's still one thing about this patch [PATCH v6 3/8], > I wanted to address: > > struct mutex lock; /* lock to protect transf_buf */ > + u8 watermark; > __le16 transf_buf __aligned(IIO_DMA_MINALIGN); > + __le16 fifo_buf[ADXL313_NUM_AXIS * ADXL313_FIFO_SIZE + 1]; > }; > > Is this correct usage of the IIO_DMA_MINALIGN? My intention here is to > have transf_buf and fifo_buf[...] aligned with the IIO_DMA_MINALIGN. > > Sorry, I should have asked this earlier. I saw the sensor operating, > but I'm unsure if perhaps DMA usage is setup correctly. Perhaps you > could drop me a line of feedback here? > > Best, > L Assuming that transf_bus and fifo_buf aren't used at the same time, which seems unlikely, this looks correct. As an example of what could be problematic would be if the driver wrote to transf_buf while fifo_buf was being used for a SPI DMA read. Then, when the DMA operation was done, it could write over transf_buf with the old value from when the DMA operation started because it was in the same memory cache line as fifo_buf.
