[PATCH v2] phy: cadence: Sierra: Do not modify register when getting parent clock

[PATCH v2] phy: cadence: Sierra: Do not modify register when getting parent clock

[Gregory CLEMENT]

The get_parent() callback for the PLL_CMNLC1 clock was incorrectly
writing to the register while determining the parent clock index. This
unintended register access forces the PHY back into training mode. If
the PHY is already configured, this unexpected change prevents it from
exiting training mode.

Remove the register write operation to ensure the PHY remains stable
during the get_parent() callback.

Fixes: da08aab940092 ("phy: cadence: Sierra: Fix to get correct parent for mux clocks")
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
---
Changes in v2:

- Removed unused variable spotted by the 0-DAY CI Kernel Test Service:
  https://lore.kernel.org/oe-kbuild-all/202603061235.hrl27Jvj-lkp@intel.com/
- Link to v1: https://lore.kernel.org/r/20260305-fix_sierra_get_parent-v1-1-a7c18e9e6c58@bootlin.com
---
 drivers/phy/cadence/phy-cadence-sierra.c | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/drivers/phy/cadence/phy-cadence-sierra.c b/drivers/phy/cadence/phy-cadence-sierra.c
index 92ab1a31646ae..dbeda7f01cbb2 100644
--- a/drivers/phy/cadence/phy-cadence-sierra.c
+++ b/drivers/phy/cadence/phy-cadence-sierra.c
@@ -698,23 +698,16 @@ static const struct phy_ops noop_ops = {
 static u8 cdns_sierra_pll_mux_get_parent(struct clk_hw *hw)
 {
 	struct cdns_sierra_pll_mux *mux = to_cdns_sierra_pll_mux(hw);
-	struct regmap_field *plllc1en_field = mux->plllc1en_field;
-	struct regmap_field *termen_field = mux->termen_field;
 	struct regmap_field *field = mux->pfdclk_sel_preg;
 	unsigned int val;
 	int index;
 
 	regmap_field_read(field, &val);
 
-	if (strstr(clk_hw_get_name(hw), clk_names[CDNS_SIERRA_PLL_CMNLC1])) {
+	if (strstr(clk_hw_get_name(hw), clk_names[CDNS_SIERRA_PLL_CMNLC1]))
 		index = clk_mux_val_to_index(hw, cdns_sierra_pll_mux_table[CMN_PLLLC1], 0, val);
-		if (index == 1) {
-			regmap_field_write(plllc1en_field, 1);
-			regmap_field_write(termen_field, 1);
-		}
-	} else {
+	else
 		index = clk_mux_val_to_index(hw, cdns_sierra_pll_mux_table[CMN_PLLLC], 0, val);
-	}
 
 	return index;
 }

---
base-commit: 11439c4635edd669ae435eec308f4ab8a0804808
change-id: 20260305-fix_sierra_get_parent-9c8435cc65e7

Best regards,
-- 
Grégory CLEMENT, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com


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Re: [PATCH v2] phy: cadence: Sierra: Do not modify register when getting parent clock

[Neil Armstrong]

On 3/6/26 11:23, Gregory CLEMENT wrote:
> The get_parent() callback for the PLL_CMNLC1 clock was incorrectly
> writing to the register while determining the parent clock index. This
> unintended register access forces the PHY back into training mode. If
> the PHY is already configured, this unexpected change prevents it from
> exiting training mode.
> 
> Remove the register write operation to ensure the PHY remains stable
> during the get_parent() callback.
> 
> Fixes: da08aab940092 ("phy: cadence: Sierra: Fix to get correct parent for mux clocks")
> Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
> ---
> Changes in v2:
> 
> - Removed unused variable spotted by the 0-DAY CI Kernel Test Service:
>    https://lore.kernel.org/oe-kbuild-all/202603061235.hrl27Jvj-lkp@intel.com/
> - Link to v1: https://lore.kernel.org/r/20260305-fix_sierra_get_parent-v1-1-a7c18e9e6c58@bootlin.com
> ---
>   drivers/phy/cadence/phy-cadence-sierra.c | 11 ++---------
>   1 file changed, 2 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/phy/cadence/phy-cadence-sierra.c b/drivers/phy/cadence/phy-cadence-sierra.c
> index 92ab1a31646ae..dbeda7f01cbb2 100644
> --- a/drivers/phy/cadence/phy-cadence-sierra.c
> +++ b/drivers/phy/cadence/phy-cadence-sierra.c
> @@ -698,23 +698,16 @@ static const struct phy_ops noop_ops = {
>   static u8 cdns_sierra_pll_mux_get_parent(struct clk_hw *hw)
>   {
>   	struct cdns_sierra_pll_mux *mux = to_cdns_sierra_pll_mux(hw);
> -	struct regmap_field *plllc1en_field = mux->plllc1en_field;
> -	struct regmap_field *termen_field = mux->termen_field;
>   	struct regmap_field *field = mux->pfdclk_sel_preg;
>   	unsigned int val;
>   	int index;
>   
>   	regmap_field_read(field, &val);
>   
> -	if (strstr(clk_hw_get_name(hw), clk_names[CDNS_SIERRA_PLL_CMNLC1])) {
> +	if (strstr(clk_hw_get_name(hw), clk_names[CDNS_SIERRA_PLL_CMNLC1]))
>   		index = clk_mux_val_to_index(hw, cdns_sierra_pll_mux_table[CMN_PLLLC1], 0, val);
> -		if (index == 1) {
> -			regmap_field_write(plllc1en_field, 1);
> -			regmap_field_write(termen_field, 1);
> -		}
> -	} else {
> +	else
>   		index = clk_mux_val_to_index(hw, cdns_sierra_pll_mux_table[CMN_PLLLC], 0, val);
> -	}
>   
>   	return index;
>   }
> 
> ---
> base-commit: 11439c4635edd669ae435eec308f4ab8a0804808
> change-id: 20260305-fix_sierra_get_parent-9c8435cc65e7
> 
> Best regards,

Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>

Thanks,
Neil

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