board: freescale: p1_p2_rdb_pc: Add workaround for non-working watchdog

If watchdog timer was already set to non-disabled value then it means that
watchdog timer was already activated, has already expired and caused CPU
reset. If this happened then due to CPLD firmware bug, writing to wd_cfg
register has no effect and therefore it is not possible to reactivate
watchdog timer again. Watchdog starts working again after CPU reset via
non-watchdog method.

Implement this workaround (reset CPU when it was reset by watchdog) to make
watchdog usable again. Watchdog timer logic on these P1/P2 RDB boards is
connected to CPLD, not to SoC itself.

Note that reset does not occur immediately after calling do_reset(), but
after few ms later as real reset is done by CPLD. So it is normal that
function do_reset() returns. Therefore hangs after calling do_reset() to
prevent CPU execution of the rest U-Boot code.

Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Peng Fan <peng.fan@nxp.com>

diff --git a/board/freescale/p1_p2_rdb_pc/p1_p2_rdb_pc.c b/board/freescale/p1_p2_rdb_pc/p1_p2_rdb_pc.c
index b7c39564325b3e9d47995be49f42a7a7d8970e41..4c0e41f987f3cbc7d5610e3a5e86910016879da2 100644 (file)
--- a/board/freescale/p1_p2_rdb_pc/p1_p2_rdb_pc.c
+++ b/board/freescale/p1_p2_rdb_pc/p1_p2_rdb_pc.c
@@ -92,6 +92,7 @@ void board_reset(void)
 void board_cpld_init(void)
 {
        struct cpld_data *cpld_data = (void *)(CONFIG_SYS_CPLD_BASE);
+       u8 prev_wd_cfg = in_8(&cpld_data->wd_cfg);
 
        out_8(&cpld_data->wd_cfg, CPLD_WD_CFG);
        out_8(&cpld_data->status_led, CPLD_STATUS_LED);
@@ -111,6 +112,26 @@ void board_cpld_init(void)
         * and it has to be done in 100ms since the last start of reset.
         */
        out_8(&cpld_data->system_rst, CPLD_SYS_RST);
+
+       /*
+        * If watchdog timer was already set to non-disabled value then it means
+        * that watchdog timer was already activated, has already expired and
+        * caused CPU reset. If this happened then due to CPLD firmware bug,
+        * writing to wd_cfg register has no effect and therefore it is not
+        * possible to reactivate watchdog timer again. Also if CPU was reset
+        * via watchdog then some peripherals like i2c do not work. Watchdog and
+        * i2c start working again after CPU reset via non-watchdog method.
+        *
+        * So in case watchdog timer register in CPLD was already enabled then
+        * disable it in CPLD and reset CPU which cause new boot. Watchdog timer
+        * is disabled few lines above, after reading CPLD previous value.
+        * This logic (disabling timer before reset) prevents reboot loop.
+        */
+       if (prev_wd_cfg != CPLD_WD_CFG) {
+               eieio();
+               do_reset(NULL, 0, 0, NULL);
+               while (1); /* do_reset() does not occur immediately */
+       }
 }
 
 void board_gpio_init(void)