linux-kernel - [PATCH v2] clk: mediatek: Allow changing PLL rate when it is off

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Message-ID: <1452482936-51852-1-git-send-email-jamesjj.liao@mediatek.com>
Date:	Mon, 11 Jan 2016 11:28:56 +0800
From:	James Liao <jamesjj.liao@...iatek.com>
To:	Matthias Brugger <matthias.bgg@...il.com>,
	Mike Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...eaurora.org>
CC:	Sascha Hauer <kernel@...gutronix.de>,
	Daniel Kurtz <djkurtz@...omium.org>,
	<srv_heupstream@...iatek.com>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>,
	<linux-mediatek@...ts.infradead.org>, <linux-clk@...r.kernel.org>,
	James Liao <jamesjj.liao@...iatek.com>
Subject: [PATCH v2] clk: mediatek: Allow changing PLL rate when it is off

Some modules may need to change its clock rate before turn on it.
So changing PLL's rate when it is off should be allowed.
This patch removes PLL enabled check before set rate, so that
PLLs can set new frequency even if they are off.

On MT8173 for example, ARMPLL's enable bit can be controlled by
other HW. That means ARMPLL may be turned on even if we (CPU / SW)
set ARMPLL's enable bit as 0. In this case, SW may want and can
still change ARMPLL's rate by changing its pcw and postdiv settings.
But without this patch, new pcw setting will not be applied because
its enable bit is 0.

Signed-off-by: James Liao <jamesjj.liao@...iatek.com>
---
 drivers/clk/mediatek/clk-pll.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/drivers/clk/mediatek/clk-pll.c b/drivers/clk/mediatek/clk-pll.c
index 966cab1..8e31fae 100644
--- a/drivers/clk/mediatek/clk-pll.c
+++ b/drivers/clk/mediatek/clk-pll.c
@@ -91,9 +91,6 @@ static void mtk_pll_set_rate_regs(struct mtk_clk_pll *pll, u32 pcw,
 		int postdiv)
 {
 	u32 con1, val;
-	int pll_en;
-
-	pll_en = readl(pll->base_addr + REG_CON0) & CON0_BASE_EN;
 
 	/* set postdiv */
 	val = readl(pll->pd_addr);
@@ -114,15 +111,13 @@ static void mtk_pll_set_rate_regs(struct mtk_clk_pll *pll, u32 pcw,
 
 	con1 = readl(pll->base_addr + REG_CON1);
 
-	if (pll_en)
-		con1 |= CON0_PCW_CHG;
+	con1 |= CON0_PCW_CHG;
 
 	writel(con1, pll->base_addr + REG_CON1);
 	if (pll->tuner_addr)
 		writel(con1 + 1, pll->tuner_addr);
 
-	if (pll_en)
-		udelay(20);
+	udelay(20);
 }
 
 /*
-- 
1.9.1