linux-kernel - [PATCH] clk: at91: clk-main: update key before writing AT91_CKGR

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Message-ID: <1596099803-1393-1-git-send-email-claudiu.beznea@microchip.com>
Date:   Thu, 30 Jul 2020 12:03:23 +0300
From:   Claudiu Beznea <claudiu.beznea@...rochip.com>
To:     <mturquette@...libre.com>, <sboyd@...nel.org>,
        <nicolas.ferre@...rochip.com>, <alexandre.belloni@...tlin.com>,
        <ludovic.desroches@...rochip.com>, <mturquette@...aro.org>,
        <bbrezillon@...nel.org>
CC:     <linux-clk@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        Claudiu Beznea <claudiu.beznea@...rochip.com>
Subject: [PATCH] clk: at91: clk-main: update key before writing AT91_CKGR_MOR

SAMA5D2 datasheet specifies on chapter 33.22.8 (PMC Clock Generator
Main Oscillator Register) that writing any value other than
0x37 on KEY field aborts the write operation. Use the key when
selecting main clock parent.

Fixes: 27cb1c2083373 ("clk: at91: rework main clk implementation")
Signed-off-by: Claudiu Beznea <claudiu.beznea@...rochip.com>
---
 drivers/clk/at91/clk-main.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/clk/at91/clk-main.c b/drivers/clk/at91/clk-main.c
index 5c83e899084f..cfae2f59df66 100644
--- a/drivers/clk/at91/clk-main.c
+++ b/drivers/clk/at91/clk-main.c
@@ -437,12 +437,17 @@ static int clk_sam9x5_main_set_parent(struct clk_hw *hw, u8 index)
 		return -EINVAL;
 
 	regmap_read(regmap, AT91_CKGR_MOR, &tmp);
-	tmp &= ~MOR_KEY_MASK;
 
 	if (index && !(tmp & AT91_PMC_MOSCSEL))
-		regmap_write(regmap, AT91_CKGR_MOR, tmp | AT91_PMC_MOSCSEL);
+		tmp = AT91_PMC_MOSCSEL;
 	else if (!index && (tmp & AT91_PMC_MOSCSEL))
-		regmap_write(regmap, AT91_CKGR_MOR, tmp & ~AT91_PMC_MOSCSEL);
+		tmp = 0;
+	else
+		return 0;
+
+	regmap_update_bits(regmap, AT91_CKGR_MOR,
+			   AT91_PMC_MOSCSEL | MOR_KEY_MASK,
+			   tmp | AT91_PMC_KEY);
 
 	while (!clk_sam9x5_main_ready(regmap))
 		cpu_relax();
-- 
2.7.4