linux-kernel - [PATCH V2 2/4] clk: imx: pll14xx: use readl to force write completed

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Date:   Thu, 14 Nov 2019 03:38:17 +0000
From:   Peng Fan <peng.fan@....com>
To:     "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>,
        Abel Vesa <abel.vesa@....com>
CC:     "kernel@...gutronix.de" <kernel@...gutronix.de>,
        dl-linux-imx <linux-imx@....com>,
        Aisheng Dong <aisheng.dong@....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>,
        Alice Guo <alice.guo@....com>,
        "will@...nel.org" <will@...nel.org>, Peng Fan <peng.fan@....com>
Subject: [PATCH V2 2/4] clk: imx: pll14xx: use readl to force write completed

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

To ensure writes to clock registers have properly completed,
add a readl after writel_relaxed. Then we could make sure
when udelay, write has been completed.

Signed-off-by: Peng Fan <peng.fan@....com>
Cc: Will Deacon <will@...nel.org>
---
 drivers/clk/imx/clk-pll14xx.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/clk/imx/clk-pll14xx.c b/drivers/clk/imx/clk-pll14xx.c
index 5b7d41d43b3b..a8af949f0848 100644
--- a/drivers/clk/imx/clk-pll14xx.c
+++ b/drivers/clk/imx/clk-pll14xx.c
@@ -205,6 +205,12 @@ static int clk_pll1416x_set_rate(struct clk_hw *hw, unsigned long drate,
 		(rate->sdiv << SDIV_SHIFT);
 	writel_relaxed(div_val, pll->base + 0x4);
 
+	/*
+	 * readl will force write completed. There is a udelay below,
+	 * we need make sure before udelay, write has been completed
+	 */
+	readl(pll->base + 0x4);
+
 	/*
 	 * According to SPEC, t3 - t2 need to be greater than
 	 * 1us and 1/FREF, respectively.
-- 
2.16.4