linux-kernel - [PATCH 5.8 450/633] clk: at91: clk-main: update key before writing AT91_CKGR

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Message-Id: <20201027135543.823316244@linuxfoundation.org>
Date:   Tue, 27 Oct 2020 14:53:13 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Claudiu Beznea <claudiu.beznea@...rochip.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.8 450/633] clk: at91: clk-main: update key before writing AT91_CKGR_MOR

From: Claudiu Beznea <claudiu.beznea@...rochip.com>

[ Upstream commit 85d071e7f19a6a9abf30476b90b3819642568756 ]

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>
Reviewed-by: Alexandre Belloni <alexandre.belloni@...tlin.com>
Link: https://lore.kernel.org/r/1598338751-20607-3-git-send-email-claudiu.beznea@microchip.com
Signed-off-by: Stephen Boyd <sboyd@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 37c22667e8319..4313ecb2af5b2 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();
-- 
2.25.1