foo.patch

From 1a5d57a5102c67358affbfd1560ccbbf692deddc Mon Sep 17 00:00:00 2001
From: Jeff Epler <jepler@gmail.com>
Date: Thu, 19 Jan 2023 07:57:06 -0600
Subject: [PATCH] clear bspi fifos before starting fifo writes

---
 src/hal/drivers/mesa-hostmot2/bspi.c     | 24 ++++++++++++++++++------
 src/hal/drivers/mesa-hostmot2/hostmot2.h |  1 +
 2 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/src/hal/drivers/mesa-hostmot2/bspi.c b/src/hal/drivers/mesa-hostmot2/bspi.c
index 1b9a491474..9397133d61 100644
--- a/src/hal/drivers/mesa-hostmot2/bspi.c
+++ b/src/hal/drivers/mesa-hostmot2/bspi.c
@@ -26,9 +26,10 @@
 
 int hm2_bspi_parse_md(hostmot2_t *hm2, int md_index) 
 {
-    // All this function actually does is allocate memory
-    // and give the bspi modules names. 
-    
+    // This function
+    //  * Allocates memory
+    //  * gives the bspi module names
+    //  * sets up a tram write to clear the TX and RX fifos every period
     
     // 
     // some standard sanity checks
@@ -78,11 +79,11 @@ int hm2_bspi_parse_md(hostmot2_t *hm2, int md_index)
     hm2->bspi.instance = (hm2_bspi_instance_t *)hal_malloc(hm2->bspi.num_instances 
                                                      * sizeof(hm2_bspi_instance_t));
     if (hm2->bspi.instance == NULL) {
-        HM2_ERR("out of memory!\n");
+        HM2_ERR("out of memory allocatin bspi instances!\n");
         r = -ENOMEM;
         goto fail0;
     }
-    
+
     for (i = 0 ; i < hm2->bspi.num_instances ; i++){
         hm2_bspi_instance_t *chan = &hm2->bspi.instance[i];
         chan->clock_freq = md->clock_freq;
@@ -97,8 +98,19 @@ int hm2_bspi_parse_md(hostmot2_t *hm2, int md_index)
         for (j = 0 ; j < 16 ; j++ ){
             chan->addr[j] = chan->base_address + j * sizeof(rtapi_u32);
         }
-        
     }
+
+    // Any write to the FIFO count register clears both the TX and RX fifos.
+    // Doing this early before the individual frame writes ensures that
+    // any weird timing issues that caused the FIFOs to be read back before
+    // they were full only causes a transient problem, rather than causing
+    // data to be skewed for the balance of the HAL session.
+    r = hm2_register_tram_write_region(hm2, hm2->bspi.instance[0].count_addr, (hm2->bspi.num_instances * sizeof(rtapi_u32)), &hm2->bspi.clear_fifos_reg);
+    if (r < 0) {
+        HM2_ERR("error registering tram write region for BSPI Fifo Clear register (%d)\n", r);
+        goto fail0;
+    }
+
     return hm2->bspi.num_instances;
 fail0:
     return r;
diff --git a/src/hal/drivers/mesa-hostmot2/hostmot2.h b/src/hal/drivers/mesa-hostmot2/hostmot2.h
index 2f3a081e42..fc0772013d 100644
--- a/src/hal/drivers/mesa-hostmot2/hostmot2.h
+++ b/src/hal/drivers/mesa-hostmot2/hostmot2.h
@@ -1270,6 +1270,7 @@ typedef struct {
     hm2_bspi_instance_t *instance;
     rtapi_u8 instances;
     rtapi_u8 num_registers;
+    rtapi_u32 *clear_fifos_reg;
 } hm2_bspi_t;
 
 //
-- 
2.34.1