Changeset 539 for trunk/kernel/kern/kernel_init.c

Timestamp:

Sep 21, 2018, 10:21:42 PM (6 years ago)

Author:

nicolas.van.phan@…

Message:

TTY MUX 4 : Multiplex TTY character sending

Now, when a thread wants to write to a tty,
when the dev_txt_write() or dev_txt_sync_write() are called,
they all call soclib_mtty_aux() with a channel number.
The soclib_mtty_aux() function will write the string char by char,
with each char preceded by the channel number, so that the receiving end
knows to which tty a character is addressed to.

N.B. dev_txt_write() makes *synchronous* writes for the moment
because unlike the vci_tty_tsar, the vci_multi_tty doesn't raise
interrupt except when a new char is received, so we can't use the
interrupt mechanism for writes.

N.B. Now, the TTY DEV threads all write to the same register (WRITE),
but when a thread sends a 2-byte (tty dest. nb. + char), the two must be
send consecutively, without another thread sending a byte in between.
Consequently, a lock has been added to guarantee this atomicity.

File:

• trunk/kernel/kern/kernel_init.c (modified) (2 diffs)

trunk/kernel/kern/kernel_init.c

@@ -88 +88 @@
 chdev_t              txt0_chdev                              CONFIG_CACHE_LINE_ALIGNED;
 
+// This variable defines the TXT0 lock for writing characters to MTY0
+__attribute__((section(".kdata")))
+spinlock_t           txt0_lock                               CONFIG_CACHE_LINE_ALIGNED;
+
 // This variables define the kernel process0 descriptor
 __attribute__((section(".kdata")))
@@ -282 +286 @@
     dev_tbl = info->int_dev;
 
+    // Initialize spinlock for writing to MTY0
+    spinlock_init(&txt0_lock);
+    
     // Loop on internal peripherals of cluster (0,0) to find MTY0
     for ( i = 0; i < dev_nr; i++ )