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@microchip.com>
Reviewed-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/1598338751-20607-3-git-send-email-claudiu.beznea@microchip.com
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

diff --git a/drivers/clk/at91/clk-main.c b/drivers/clk/at91/clk-main.c
index 5c83e89..cfae2f5 100644 (file)
--- 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();