asix-sigma: improve robustness of firmware download, delay and retry

[libsigrok.git] / src / hardware / asix-sigma / protocol.c

diff --git a/src/hardware/asix-sigma/protocol.c b/src/hardware/asix-sigma/protocol.c
index 9819e892508632e73bb2c8a7326b083acefed5c6..68bb83e558b794b0ae9f2837193f4f4ea85d0df7 100644 (file)
--- a/src/hardware/asix-sigma/protocol.c
+++ b/src/hardware/asix-sigma/protocol.c
@@ -313,10 +313,16 @@ SR_PRIV int sigma_write_trigger_lut(struct triggerlut *lut, struct dev_context *
 /*
  * Initiate slave serial mode for configuration download. Which is done
  * by pulsing PROG_B and sensing INIT_B. Make sure CCLK is idle before
- * initiating the configuration download. Run a "suicide sequence" first
- * to terminate the regular FPGA operation before reconfiguration.
+ * initiating the configuration download.
+ *
+ * Run a "suicide sequence" first to terminate the regular FPGA operation
+ * before reconfiguration. The FTDI cable is single channel, and shares
+ * pins which are used for data communication in FIFO mode with pins that
+ * are used for FPGA configuration in bitbang mode. Hardware defaults for
+ * unconfigured hardware, and runtime conditions after FPGA configuration
+ * need to cooperate such that re-configuration of the FPGA can start.
  */
-static int sigma_fpga_init_bitbang(struct dev_context *devc)
+static int sigma_fpga_init_bitbang_once(struct dev_context *devc)
 {
        uint8_t suicide[] = {
                BB_PIN_D7 | BB_PIN_D2,
@@ -348,9 +354,11 @@ static int sigma_fpga_init_bitbang(struct dev_context *devc)
        sigma_write(suicide, sizeof(suicide), devc);
        sigma_write(suicide, sizeof(suicide), devc);
        sigma_write(suicide, sizeof(suicide), devc);
+       g_usleep(10 * 1000);
 
        /* Section 2. part 2), pulse PROG. */
        sigma_write(init_array, sizeof(init_array), devc);
+       g_usleep(10 * 1000);
        ftdi_usb_purge_buffers(&devc->ftdic);
 
        /* Wait until the FPGA asserts INIT_B. */
@@ -367,6 +375,27 @@ static int sigma_fpga_init_bitbang(struct dev_context *devc)
        return SR_ERR_TIMEOUT;
 }
 
+/*
+ * This is belt and braces. Re-run the bitbang initiation sequence a few
+ * times should first attempts fail. Failure is rare but can happen (was
+ * observed during driver development).
+ */
+static int sigma_fpga_init_bitbang(struct dev_context *devc)
+{
+       size_t retries;
+       int ret;
+
+       retries = 10;
+       while (retries--) {
+               ret = sigma_fpga_init_bitbang_once(devc);
+               if (ret == SR_OK)
+                       return ret;
+               if (ret != SR_ERR_TIMEOUT)
+                       return ret;
+       }
+       return ret;
+}
+
 /*
  * Configure the FPGA for logic-analyzer mode.
  */