board/hyperdebug: Use dedicated memory buffer for gpio monitoring

HyperDebug can be instructed to capture edge events on a subset of GPIO
pins.  The current use of `common/shared_mem.h` conflicts with its use
by e.g. SPI.

This CL introduces a dedicated memory area in `hyperdebug/gpio.c`.  For
now, only a single allocation of that area is implemented.  We may want
to allow the called to request a certain buffer size, and split the
available are between buffer for disjoint subsets of GPIO pins being
monitored.

BUG=b:279752946
TEST=opentitantool spi tpm read register,  while gpio monitoring

Change-Id: I9cc9b016b964b4db1cb31a048126deeacfef9b99
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/4481050
Reviewed-by: Jett Rink <jettrink@chromium.org>
Commit-Queue: Jes Klinke <jbk@chromium.org>
Tested-by: Jes Klinke <jbk@chromium.org>

1 files changed, 36 insertions, 8 deletions

diff --git a/board/hyperdebug/gpio.c b/board/hyperdebug/gpio.c
index 53a4929b3c..fff62ee233 100644
--- a/board/hyperdebug/gpio.c
+++ b/board/hyperdebug/gpio.c
@@ -12,7 +12,6 @@
 #include "gpio.h"
 #include "hooks.h"
 #include "registers.h"
-#include "shared_mem.h"
 #include "task.h"
 #include "timer.h"
 #include "util.h"
@@ -101,6 +100,36 @@ struct monitoring_slot_t {
 struct monitoring_slot_t monitoring_slots[16];
 
 /*
+ * Memory area used for allocation of cyclic buffers.  (Currently the
+ * implementation supports only a single allocation.)
+ */
+uint8_t buffer_area[sizeof(struct cyclic_buffer_header_t) + 8192];
+bool buffer_area_in_use = false;
+
+static struct cyclic_buffer_header_t *allocate_cyclic_buffer(size_t size)
+{
+	struct cyclic_buffer_header_t *res =
+		(struct cyclic_buffer_header_t *)buffer_area;
+	if (buffer_area_in_use) {
+		/* No support for multiple smaller allocations, yet. */
+		return 0;
+	}
+	if (sizeof(struct cyclic_buffer_header_t) + size >
+	    sizeof(buffer_area)) {
+		/* Requested size exceeds the capacity of the area. */
+		return 0;
+	}
+	buffer_area_in_use = true;
+	res->size = size;
+	return res;
+}
+
+static void free_cyclic_buffer(struct cyclic_buffer_header_t *buf)
+{
+	buffer_area_in_use = false;
+}
+
+/*
  * Counts unacknowledged buffer overflows.  Whenever non-zero, the red LED
  * will flash.
  */
@@ -251,7 +280,7 @@ static void stop_all_gpio_monitoring(void)
 		num_cur_monitoring--;
 		if (buffer_header->overflow)
 			atomic_sub(&num_cur_error_conditions, 1);
-		shared_mem_release((char *)buffer_header);
+		free_cyclic_buffer(buffer_header);
 	}
 }
 
@@ -521,14 +550,13 @@ static int command_gpio_monitoring_start(int argc, const char **argv)
 	 * All the requested signals were available for monitoring, and their
 	 * slots have been marked as reserved for the respective signal.
 	 */
-	rv = shared_mem_acquire(sizeof(struct cyclic_buffer_header_t) +
-					cyclic_buffer_size,
-				(char **)&buf);
-	if (rv != EC_SUCCESS)
+	buf = allocate_cyclic_buffer(cyclic_buffer_size);
+	if (!buf) {
+		rv = EC_ERROR_BUSY;
 		goto out_cleanup;
+	}
 
 	buf->head = buf->tail = 0;
-	buf->size = cyclic_buffer_size;
 	buf->overflow = 0;
 	buf->num_signals = gpio_num;
 	buf->signal_bits = 0;
@@ -790,7 +818,7 @@ static int command_gpio_monitoring_stop(int argc, const char **argv)
 	if (buf->overflow)
 		atomic_sub(&num_cur_error_conditions, 1);
 
-	shared_mem_release((char *)buf);
+	free_cyclic_buffer(buf);
 	return EC_SUCCESS;
 }