linux-kernel - [PATCH 2/6] clk: ingenic: Support specifying "wait for clock stable" delay

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Message-Id: <20180520163117.14125-2-paul@crapouillou.net>
Date:   Sun, 20 May 2018 16:31:13 +0000
From:   Paul Cercueil <paul@...pouillou.net>
To:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>
Cc:     James Hogan <jhogan@...nel.org>, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org, Paul Cercueil <paul@...pouillou.net>
Subject: [PATCH 2/6] clk: ingenic: Support specifying "wait for clock stable" delay

Some clocks need a small delay after being ungated to run stable, as
using them too soon might result in hardware lockups.

Signed-off-by: Paul Cercueil <paul@...pouillou.net>
---
 drivers/clk/ingenic/cgu.c | 3 +++
 drivers/clk/ingenic/cgu.h | 2 ++
 2 files changed, 5 insertions(+)

diff --git a/drivers/clk/ingenic/cgu.c b/drivers/clk/ingenic/cgu.c
index 4b31145eb8aa..5ef7d9ba2195 100644
--- a/drivers/clk/ingenic/cgu.c
+++ b/drivers/clk/ingenic/cgu.c
@@ -512,6 +512,9 @@ static int ingenic_clk_enable(struct clk_hw *hw)
 		spin_lock_irqsave(&cgu->lock, flags);
 		ingenic_cgu_gate_set(cgu, &clk_info->gate, false);
 		spin_unlock_irqrestore(&cgu->lock, flags);
+
+		if (clk_info->gate.delay_us)
+			udelay(clk_info->gate.delay_us);
 	}
 
 	return 0;
diff --git a/drivers/clk/ingenic/cgu.h b/drivers/clk/ingenic/cgu.h
index 4d2e3fad0e30..542192376ebf 100644
--- a/drivers/clk/ingenic/cgu.h
+++ b/drivers/clk/ingenic/cgu.h
@@ -112,11 +112,13 @@ struct ingenic_cgu_fixdiv_info {
  * @reg: offset of the gate control register within the CGU
  * @bit: offset of the bit in the register that controls the gate
  * @clear_to_gate: if set, the clock is gated when the bit is cleared
+ * @delay_us: delay in microseconds after which the clock is considered stable
  */
 struct ingenic_cgu_gate_info {
 	unsigned reg;
 	u8 bit;
 	bool clear_to_gate;
+	u16 delay_us;
 };
 
 /**
-- 
2.17.0