fbcon: set a default value to blink interval
authorJean-Philippe Brucker <jean-philippe.brucker@arm.com>
Mon, 15 Feb 2016 18:41:33 +0000 (18:41 +0000)
committerTomi Valkeinen <tomi.valkeinen@ti.com>
Fri, 26 Feb 2016 11:19:55 +0000 (13:19 +0200)
commita1e533ec07d583d01349ef13c0c965b8633e1b91
treee894dd45f130d60347d68993a4ce15c51db81756
parent81f70ba233d5f660e1ea5fe23260ee323af5d53a
fbcon: set a default value to blink interval

Since commit 27a4c827c34ac4256a190cc9d24607f953c1c459
fbcon: use the cursor blink interval provided by vt

two attempts have been made at fixing a possible hang caused by
cursor_timer_handler. That function registers a timer to be triggered at
"jiffies + fbcon_ops.cur_blink_jiffies".

A new case had been encountered during initialisation of clcd-pl11x:

    fbcon_fb_registered
    do_fbcon_takeover

    ->  do_register_con_driver
        fbcon_startup
    (A) add_cursor_timer (with cur_blink_jiffies = 0)

    ->  do_bind_con_driver
        visual_init
        fbcon_init
    (B) cur_blink_jiffies = msecs_to_jiffies(vc->vc_cur_blink_ms);

If we take an softirq anywhere between A and B (and we do),
cursor_timer_handler executes indefinitely.

Instead of patching all possible paths that lead to this case one at a
time, fix the issue at the source and initialise cur_blink_jiffies to
200ms when allocating fbcon_ops. This was its default value before
aforesaid commit. fbcon_cursor or fbcon_init will refine this value
downstream.

Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
Cc: <stable@vger.kernel.org> # v4.2
Tested-by: Scot Doyle <lkml14@scotdoyle.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
drivers/video/console/fbcon.c