linux-kernel - [PATCH V2 4/4] clk: imx: composite-8m: use relaxed io api

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Date:   Thu, 14 Nov 2019 03:38:28 +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 4/4] clk: imx: composite-8m: use relaxed io api

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

writel/readl has a barrier, however that barrier is not needed,
because device memory mapping is nGnRE mapping and access is
in order and clk driver has spin lock or other lock to make
sure write finished. It is ok to use relaxed api here, no need
to use stronger readl/writel

Signed-off-by: Peng Fan <peng.fan@....com>
---
 drivers/clk/imx/clk-composite-8m.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/clk/imx/clk-composite-8m.c b/drivers/clk/imx/clk-composite-8m.c
index 20f7c91c03d2..513dc57483d0 100644
--- a/drivers/clk/imx/clk-composite-8m.c
+++ b/drivers/clk/imx/clk-composite-8m.c
@@ -31,14 +31,14 @@ static unsigned long imx8m_clk_composite_divider_recalc_rate(struct clk_hw *hw,
 	unsigned int prediv_value;
 	unsigned int div_value;
 
-	prediv_value = readl(divider->reg) >> divider->shift;
+	prediv_value = readl_relaxed(divider->reg) >> divider->shift;
 	prediv_value &= clk_div_mask(divider->width);
 
 	prediv_rate = divider_recalc_rate(hw, parent_rate, prediv_value,
 						NULL, divider->flags,
 						divider->width);
 
-	div_value = readl(divider->reg) >> PCG_DIV_SHIFT;
+	div_value = readl_relaxed(divider->reg) >> PCG_DIV_SHIFT;
 	div_value &= clk_div_mask(PCG_DIV_WIDTH);
 
 	return divider_recalc_rate(hw, prediv_rate, div_value, NULL,
@@ -104,13 +104,13 @@ static int imx8m_clk_composite_divider_set_rate(struct clk_hw *hw,
 
 	spin_lock_irqsave(divider->lock, flags);
 
-	val = readl(divider->reg);
+	val = readl_relaxed(divider->reg);
 	val &= ~((clk_div_mask(divider->width) << divider->shift) |
 			(clk_div_mask(PCG_DIV_WIDTH) << PCG_DIV_SHIFT));
 
 	val |= (u32)(prediv_value  - 1) << divider->shift;
 	val |= (u32)(div_value - 1) << PCG_DIV_SHIFT;
-	writel(val, divider->reg);
+	writel_relaxed(val, divider->reg);
 
 	spin_unlock_irqrestore(divider->lock, flags);
 
-- 
2.16.4