[v2,2/3] clk: at91: clk-main: update key before writing AT91_CKGR_MOR

Commit Message

Claudiu Beznea Aug. 25, 2020, 6:59 a.m. UTC

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 <[e-mail]>
Reviewed-by: Alexandre Belloni <[e-mail]>
---
 drivers/clk/at91/clk-main.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

Comments

Stephen Boyd Oct. 14, 2020, 2:59 a.m. UTC | #1

Quoting Claudiu Beznea (2020-08-24 23:59:10)
> 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 <[e-mail]>
> Reviewed-by: Alexandre Belloni <[e-mail]>
> ---

Applied to clk-next

Patch

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();