linux-kernel - [PATCH] clk: imx: pll14xx: avoid glitch when set rate

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Date:   Tue, 20 Aug 2019 02:17:46 +0000
From:   Peng Fan <peng.fan@....com>
To:     "mturquette@...libre.com" <mturquette@...libre.com>,
        "sboyd@...nel.org" <sboyd@...nel.org>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>
CC:     "kernel@...gutronix.de" <kernel@...gutronix.de>,
        dl-linux-imx <linux-imx@....com>,
        Anson Huang <anson.huang@....com>,
        Jacky Bai <ping.bai@....com>, Abel Vesa <abel.vesa@....com>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Peng Fan <peng.fan@....com>
Subject: [PATCH] clk: imx: pll14xx: avoid glitch when set rate

From: Peng Fan <peng.fan@....com>

According to PLL1443XA and PLL1416X spec,
"When BYPASS is 0 and RESETB is changed from 0 to 1, FOUT starts to
output unstable clock until lock time passes. PLL1416X/PLL1443XA may
generate a glitch at FOUT."

So set BYPASS when RESETB is changed from 0 to 1 to avoid glitch.
In the end of set rate, BYPASS will be cleared.

Fixes: 8646d4dcc7fb ("clk: imx: Add PLLs driver for imx8mm soc")
Signed-off-by: Peng Fan <peng.fan@....com>
---
 drivers/clk/imx/clk-pll14xx.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/clk/imx/clk-pll14xx.c b/drivers/clk/imx/clk-pll14xx.c
index b7213023b238..bd072556bc44 100644
--- a/drivers/clk/imx/clk-pll14xx.c
+++ b/drivers/clk/imx/clk-pll14xx.c
@@ -191,6 +191,10 @@ static int clk_pll1416x_set_rate(struct clk_hw *hw, unsigned long drate,
 	tmp &= ~RST_MASK;
 	writel_relaxed(tmp, pll->base);
 
+	/* Enable BYPASS */
+	tmp |= BYPASS_MASK;
+	writel(tmp, pll->base);
+
 	div_val = (rate->mdiv << MDIV_SHIFT) | (rate->pdiv << PDIV_SHIFT) |
 		(rate->sdiv << SDIV_SHIFT);
 	writel_relaxed(div_val, pll->base + 0x4);
@@ -250,6 +254,10 @@ static int clk_pll1443x_set_rate(struct clk_hw *hw, unsigned long drate,
 	tmp &= ~RST_MASK;
 	writel_relaxed(tmp, pll->base);
 
+	/* Enable BYPASS */
+	tmp |= BYPASS_MASK;
+	writel_relaxed(tmp, pll->base);
+
 	div_val = (rate->mdiv << MDIV_SHIFT) | (rate->pdiv << PDIV_SHIFT) |
 		(rate->sdiv << SDIV_SHIFT);
 	writel_relaxed(div_val, pll->base + 0x4);
-- 
2.16.4