Clear the PCS_TX_SWING_FULL field mask before setting the new value
in PHY_CTRL5 register. Without clearing the mask first, the OR operation
could leave previously set bits, resulting in incorrect
register configuration.

Fixes: 63c85ad0cd81 ("phy: fsl-imx8mp-usb: add support for phy tuning")
Suggested-by: Pierluigi Passaro <pierluigi.p@variscite.com>
Signed-off-by: Stefano Radaelli <stefano.r@variscite.com>
---
 drivers/phy/freescale/phy-fsl-imx8mq-usb.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/phy/freescale/phy-fsl-imx8mq-usb.c b/drivers/phy/freescale/phy-fsl-imx8mq-usb.c
index ad8a55012e42..9458b6e5fcf4 100644
--- a/drivers/phy/freescale/phy-fsl-imx8mq-usb.c
+++ b/drivers/phy/freescale/phy-fsl-imx8mq-usb.c
@@ -504,6 +504,7 @@ static void imx8m_phy_tune(struct imx8mq_usb_phy *imx_phy)
 
 	if (imx_phy->pcs_tx_swing_full != PHY_TUNE_DEFAULT) {
 		value = readl(imx_phy->base + PHY_CTRL5);
+		value &= ~PHY_CTRL5_PCS_TX_SWING_FULL_MASK;
 		value |= FIELD_PREP(PHY_CTRL5_PCS_TX_SWING_FULL_MASK,
 				   imx_phy->pcs_tx_swing_full);
 		writel(value, imx_phy->base + PHY_CTRL5);

base-commit: ea1013c1539270e372fc99854bc6e4d94eaeff66
-- 
2.47.3

Hi Stefano,

On Thu, Dec 18, 2025 at 2:50 PM Stefano Radaelli
<stefano.radaelli21@gmail.com> wrote:
>
> Clear the PCS_TX_SWING_FULL field mask before setting the new value
> in PHY_CTRL5 register. Without clearing the mask first, the OR operation
> could leave previously set bits, resulting in incorrect
> register configuration.

The change looks good to me, but the Subject is a bit misleading.

It gives the impression that PCS_TX_SWING_FULL is a register.

What about:

phy: fsl-imx8mq-usb: Clear the PCS_TX_SWING_FULL field before using it

Hi Fabio,
> 
> The change looks good to me, but the Subject is a bit misleading.
> 
> It gives the impression that PCS_TX_SWING_FULL is a register.
> 
> What about:
> 
> phy: fsl-imx8mq-usb: Clear the PCS_TX_SWING_FULL field before using it

Thank you for the review! You're absolutely right, the subject was
misleading. I'll send a v2 with the improved subject line you suggested.

Best regards,
Stefano