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pandad: guarantee SPI slave turnaround time (#38464)

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pandad: add SPI turnaround delay

Co-authored-by: Adeeb Shihadeh <adeebshihadeh@gmail.com>
This commit is contained in:
CzokNorris
2026-08-05 07:41:16 +02:00
committed by GitHub
parent 2e4de38eb8
commit aa0ac919ba
1 changed files with 11 additions and 0 deletions
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openpilot/selfdrive/pandad/spi.cc
+11
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@@ -29,6 +29,12 @@ enum SpiError {
const unsigned int SPI_ACK_TIMEOUT = 500; // milliseconds
const std::string SPI_DEVICE = "/dev/spidev0.0";
// TODO: fix SPI turnaround synchronization at the protocol level.
static uint64_t spi_last_bus_activity_ns = 0; // protected by hw_lock
static void wait_for_spi_turnaround(uint64_t start_ns) {
while ((nanos_since_boot() - start_ns) < 400000) {}
}
class LockEx {
public:
@@ -319,6 +325,8 @@ int PandaSpiHandle::spi_transfer(uint8_t endpoint, uint8_t *tx_data, uint16_t tx
assert(tx_len < SPI_BUF_SIZE);
assert(max_rx_len < SPI_BUF_SIZE);
wait_for_spi_turnaround(spi_last_bus_activity_ns);
xfer_count++;
header = {
.sync = SPI_SYNC,
@@ -347,6 +355,7 @@ int PandaSpiHandle::spi_transfer(uint8_t endpoint, uint8_t *tx_data, uint16_t tx
if (ret < 0) {
goto fail;
}
wait_for_spi_turnaround(nanos_since_boot());
// Send data
if (tx_data != NULL) {
@@ -389,6 +398,7 @@ int PandaSpiHandle::spi_transfer(uint8_t endpoint, uint8_t *tx_data, uint16_t tx
memcpy(rx_data, rx_buf + 3, rx_data_len);
}
spi_last_bus_activity_ns = nanos_since_boot();
return rx_data_len;
fail:
@@ -403,6 +413,7 @@ fail:
}
}
spi_last_bus_activity_ns = nanos_since_boot();
if (ret >= 0) ret = -1;
return ret;
}