linux-kernel - [PATCH V3 1/4] clk: imx: pll14xx: avoid glitch when set rate

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 9 Sep 2019 03:39:34 +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>,
        Leonard Crestez <leonard.crestez@....com>,
        Peng Fan <peng.fan@....com>
Subject: [PATCH V3 1/4] 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.

When prepare clock, also need to take care to avoid glitch. So
we also follow Spec to set BYPASS before RESETB changed from 0 to 1.
And add a check if the RESETB is already 0, directly return 0;

Fixes: 8646d4dcc7fb ("clk: imx: Add PLLs driver for imx8mm soc")
Reviewed-by: Leonard Crestez <leonard.crestez@....com>
Signed-off-by: Peng Fan <peng.fan@....com>
---

V3:
 None
V2:
  Avoid glitch when prepare
  update commit log

 drivers/clk/imx/clk-pll14xx.c | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/imx/clk-pll14xx.c b/drivers/clk/imx/clk-pll14xx.c
index b7213023b238..656f48b002dd 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);
@@ -283,16 +291,28 @@ static int clk_pll14xx_prepare(struct clk_hw *hw)
 {
 	struct clk_pll14xx *pll = to_clk_pll14xx(hw);
 	u32 val;
+	int ret;
 
 	/*
 	 * RESETB = 1 from 0, PLL starts its normal
 	 * operation after lock time
 	 */
 	val = readl_relaxed(pll->base + GNRL_CTL);
+	if (val & RST_MASK)
+		return 0;
+	val |= BYPASS_MASK;
+	writel_relaxed(val, pll->base + GNRL_CTL);
 	val |= RST_MASK;
 	writel_relaxed(val, pll->base + GNRL_CTL);
 
-	return clk_pll14xx_wait_lock(pll);
+	ret = clk_pll14xx_wait_lock(pll);
+	if (ret)
+		return ret;
+
+	val &= ~BYPASS_MASK;
+	writel_relaxed(val, pll->base + GNRL_CTL);
+
+	return 0;
 }
 
 static int clk_pll14xx_is_prepared(struct clk_hw *hw)
-- 
2.16.4