linux-kernel - [PATCH] clocksource/drivers/dw

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Date:   Thu, 27 Sep 2018 16:22:51 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     dinguyen@...nel.org
Cc:     tglx@...utronix.de, marex@...x.de,
        linux-kernel@...r.kernel.org (open list:CLOCKSOURCE, CLOCKEVENT DRIVERS)
Subject: [PATCH] clocksource/drivers/dw_apb: Add reset control

From: Dinh Nguyen <dinguyen@...nel.org>

Add code to retrieve the reset property from the dw-apb timers and if
the property is available, the safe operation is to assert the timer
into reset, and followed by a deassert of the timer reset (brings the
timer out of reset).

This patch is needed for systems where the bootloader has left the timer
not used in reset.

 - Trivial conflict with commit a74bd1ad7a:
    "Convert to using %pOFn instead of device_node.name"

Signed-off-by: Marek Vasut <marex@...x.de>
Signed-off-by: Dinh Nguyen <dinguyen@...nel.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
---
 drivers/clocksource/dw_apb_timer_of.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/clocksource/dw_apb_timer_of.c b/drivers/clocksource/dw_apb_timer_of.c
index fabaa29..db410ac 100644
--- a/drivers/clocksource/dw_apb_timer_of.c
+++ b/drivers/clocksource/dw_apb_timer_of.c
@@ -22,6 +22,7 @@
 #include <linux/of_address.h>
 #include <linux/of_irq.h>
 #include <linux/clk.h>
+#include <linux/reset.h>
 #include <linux/sched_clock.h>
 
 static void __init timer_get_base_and_rate(struct device_node *np,
@@ -29,6 +30,7 @@ static void __init timer_get_base_and_rate(struct device_node *np,
 {
 	struct clk *timer_clk;
 	struct clk *pclk;
+	struct reset_control *rstc;
 
 	*base = of_iomap(np, 0);
 
@@ -36,6 +38,16 @@ static void __init timer_get_base_and_rate(struct device_node *np,
 		panic("Unable to map regs for %pOFn", np);
 
 	/*
+	 * Reset the timer if the reset control is available, wiping
+	 * out the state the firmware may have left it
+	 */
+	rstc = of_reset_control_get(np, NULL);
+	if (!IS_ERR(rstc)) {
+		reset_control_assert(rstc);
+		reset_control_deassert(rstc);
+	}
+
+	/*
 	 * Not all implementations use a periphal clock, so don't panic
 	 * if it's not present
 	 */
-- 
2.7.4