wip

panda/drivers/spi/spi_panda.h

@@ -0,0 +1,160 @@
+#include <linux/delay.h>
+#include <linux/spi/spi.h>
+#include <linux/spi/spidev.h>
+
+#define SPI_SYNC 0x5AU
+#define SPI_HACK 0x79U
+#define SPI_DACK 0x85U
+#define SPI_NACK 0x1FU
+#define SPI_CHECKSUM_START 0xABU
+
+struct __attribute__((packed)) spi_header {
+  u8 sync;
+  u8 endpoint;
+  uint16_t tx_len;
+  uint16_t max_rx_len;
+};
+
+struct spi_panda_transfer {
+  __u64 rx_buf;
+  __u64 tx_buf;
+  __u32 tx_length;
+  __u32 rx_length_max;
+  __u32 timeout;
+  __u8 endpoint;
+  __u8 expect_disconnect;
+};
+
+static u8 panda_calc_checksum(u8 *buf, u16 length) {
+  int i;
+  u8 checksum = SPI_CHECKSUM_START;
+  for (i = 0U; i < length; i++) {
+    checksum ^= buf[i];
+  }
+  return checksum;
+}
+
+static long panda_wait_for_ack(struct spidev_data *spidev, u8 ack_val, u8 length) {
+  int i;
+  int ret;
+  for (i = 0; i < 1000; i++) {
+    ret = spidev_sync_read(spidev, length);
+    if (ret < 0) {
+      return ret;
+    }
+
+    if (spidev->rx_buffer[0] == ack_val) {
+      return 0;
+    } else if (spidev->rx_buffer[0] == SPI_NACK) {
+      return -2;
+    }
+    if (i > 20) usleep_range(10, 20);
+  }
+  return -1;
+}
+
+static long panda_transfer_raw(struct spidev_data *spidev, struct spi_device *spi, unsigned long arg) {
+  u16 rx_len;
+  long retval = -1;
+  struct spi_header header;
+  struct spi_panda_transfer pt;
+
+  struct spi_transfer t = {
+    .len = 0,
+    .tx_buf = spidev->tx_buffer,
+    .rx_buf = spidev->rx_buffer,
+    .speed_hz = spidev->spi->max_speed_hz,
+  };
+
+  struct spi_message m;
+  spi_message_init(&m);
+  spi_message_add_tail(&t, &m);
+
+  // read struct from user
+  if (!access_ok(VERIFY_WRITE, arg, sizeof(pt))) {
+    return -1;
+  }
+  if (copy_from_user(&pt, (void __user *)arg, sizeof(pt))) {
+    return -1;
+  }
+  dev_dbg(&spi->dev, "ep: %d, tx len: %d\n", pt.endpoint, pt.tx_length);
+
+  // send header
+  header.sync = 0x5a;
+  header.endpoint = pt.endpoint;
+  header.tx_len = pt.tx_length;
+  header.max_rx_len = pt.rx_length_max;
+  memcpy(spidev->tx_buffer, &header, sizeof(header));
+  spidev->tx_buffer[sizeof(header)] = panda_calc_checksum(spidev->tx_buffer, sizeof(header));
+
+  t.len = sizeof(header) + 1;
+  retval = spidev_sync(spidev, &m);
+  if (retval < 0) {
+    dev_dbg(&spi->dev, "spi xfer failed %ld\n", retval);
+    return retval;
+  }
+
+  // wait for ACK
+  retval = panda_wait_for_ack(spidev, SPI_HACK, 1);
+  if (retval < 0) {
+    dev_dbg(&spi->dev, "no header ack %ld\n", retval);
+    return retval;
+  }
+
+  // send data
+  dev_dbg(&spi->dev, "sending data\n");
+  retval = copy_from_user(spidev->tx_buffer, (const u8 __user *)(uintptr_t)pt.tx_buf, pt.tx_length);
+  spidev->tx_buffer[pt.tx_length] = panda_calc_checksum(spidev->tx_buffer, pt.tx_length);
+  t.len = pt.tx_length + 1;
+  retval = spidev_sync(spidev, &m);
+
+  if (pt.expect_disconnect) {
+    return 0;
+  }
+
+  // wait for ACK
+  retval = panda_wait_for_ack(spidev, SPI_DACK, 3);
+  if (retval < 0) {
+    dev_dbg(&spi->dev, "no data ack\n");
+    return retval;
+  }
+
+  // get response
+  t.rx_buf = spidev->rx_buffer + 3;
+  rx_len = (spidev->rx_buffer[2] << 8) | (spidev->rx_buffer[1]);
+  dev_dbg(&spi->dev, "rx len %u\n", rx_len);
+  if (rx_len > pt.rx_length_max) {
+    dev_dbg(&spi->dev, "RX len greater than max\n");
+    return -1;
+  }
+
+  // do the read
+  t.len = rx_len + 1;
+  retval = spidev_sync(spidev, &m);
+  if (retval < 0) {
+    dev_dbg(&spi->dev, "spi xfer failed %ld\n", retval);
+    return retval;
+  }
+  if (panda_calc_checksum(spidev->rx_buffer, 3 + rx_len + 1) != 0) {
+    dev_dbg(&spi->dev, "bad checksum\n");
+    return -1;
+  }
+
+  retval = copy_to_user((u8 __user *)(uintptr_t)pt.rx_buf, spidev->rx_buffer + 3, rx_len);
+
+  return rx_len;
+}
+
+static long panda_transfer(struct spidev_data *spidev, struct spi_device *spi, unsigned long arg) {
+  int i;
+  int ret;
+  dev_dbg(&spi->dev, "=== XFER start ===\n");
+  for (i = 0; i < 20; i++) {
+    ret = panda_transfer_raw(spidev, spi, arg);
+    if (ret >= 0) {
+      break;
+    }
+  }
+  dev_dbg(&spi->dev, "took %d tries\n", i+1);
+  return ret;
+}