From 4a292ac0dacc6ebbfc05b95e8bce0091530028e2 Mon Sep 17 00:00:00 2001
From: Rahix <rahix@rahix.de>
Date: Sun, 21 Jul 2019 23:02:45 +0200
Subject: [PATCH] workaround(cdcacm): Fix CDC-ACM lockup on host hangup
This patch is a workaround for #54. A lockup is detected if more than
4096 attempts to write to the USB FIFO fail. If this condition is
detected, CDC-ACM is disabled until the next reboot.
Signed-off-by: Rahix <rahix@rahix.de>
---
epicardium/cdcacm.c | 12 ++++++++----
lib/sdk/Libraries/MAXUSB/src/devclass/cdc_acm.c | 6 ++++++
2 files changed, 14 insertions(+), 4 deletions(-)
diff --git a/epicardium/cdcacm.c b/epicardium/cdcacm.c
index 19b1dcfe..cead3780 100644
--- a/epicardium/cdcacm.c
+++ b/epicardium/cdcacm.c
@@ -199,10 +199,14 @@ uint8_t cdcacm_read(void)
void cdcacm_write(uint8_t *data, int len)
{
- while (acm_present()) {
- // TODO: This might fail horribly
- if (acm_write(data, len) == len) {
- break;
+ static int lockup_disable = 0;
+ if (acm_present() && !lockup_disable) {
+ int ret = acm_write(data, len);
+ if (ret < 0) {
+ LOG_ERR("cdcacm", "fifo lockup detected");
+ lockup_disable = 1;
+ } else if (ret != len) {
+ LOG_WARN("cdcacm", "write length mismatch, got %d", ret);
}
}
}
diff --git a/lib/sdk/Libraries/MAXUSB/src/devclass/cdc_acm.c b/lib/sdk/Libraries/MAXUSB/src/devclass/cdc_acm.c
index 92bf8df2..c85ca2b8 100644
--- a/lib/sdk/Libraries/MAXUSB/src/devclass/cdc_acm.c
+++ b/lib/sdk/Libraries/MAXUSB/src/devclass/cdc_acm.c
@@ -329,10 +329,12 @@ int acm_read(uint8_t *buf, unsigned int len)
int acm_write(uint8_t *buf, unsigned int len)
{
unsigned int i = 0;
+ unsigned int failcount = 0;
/* Write data into the FIFO */
while (len > 0) {
if (fifo_put8(&wfifo, buf[i]) == 0) {
+ failcount = 0;
/* Success */
i++; len--;
} else {
@@ -340,6 +342,10 @@ int acm_write(uint8_t *buf, unsigned int len)
if (wreq.reqlen == 0) {
svc_in_to_host(&wreq);
}
+
+ if (failcount++ > 4096) {
+ return -1;
+ }
}
}
--
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