Tegra devices have an 'sfsel' bit field that determines whether a pin
operates in SFIO (Special Function I/O) or GPIO mode. Currently,
tegra_pinctrl_gpio_disable_free() sets this bit when releasing a GPIO.

However, tegra_pinctrl_set_mux() can be called independently in certain
code paths where gpio_disable_free() is not invoked. In such cases, failing
to set the SFIO mode could lead to incorrect pin configurations, resulting
in functional issues for peripherals relying on SFIO.

This patch ensures that whenever set_mux() is called, the SFIO mode is
correctly set in the Mux Register if the 'sfsel' bit is present. This
prevents situations where the pin remains in GPIO mode despite being
configured for SFIO use.

Fixes: 59b67585e242 ("pinctrl: add a driver for NVIDIA Tegra")
Signed-off-by: Prathamesh Shete <pshete@nvidia.com>
---
v1->v2: Updated commit message describing the need.
v1: https://lore.kernel.org/linux-tegra/CACRpkdY2E+8quTVVkCqoph-h6Ye+hEb+z+D5+2g=ArmfLpGR1A@mail.gmail.com/

 drivers/pinctrl/tegra/pinctrl-tegra.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/pinctrl/tegra/pinctrl-tegra.c b/drivers/pinctrl/tegra/pinctrl-tegra.c
index abe31fead395..27823e420734 100644
--- a/drivers/pinctrl/tegra/pinctrl-tegra.c
+++ b/drivers/pinctrl/tegra/pinctrl-tegra.c
@@ -270,6 +270,9 @@ static int tegra_pinctrl_set_mux(struct pinctrl_dev *pctldev,
 	val = pmx_readl(pmx, g->mux_bank, g->mux_reg);
 	val &= ~(0x3 << g->mux_bit);
 	val |= i << g->mux_bit;
+	/* Set the SFIO/GPIO selection to SFIO when under pinmux control*/
+	if (pmx->soc->sfsel_in_mux)
+		val |= (1 << g->sfsel_bit);
 	pmx_writel(pmx, val, g->mux_bank, g->mux_reg);
 
 	return 0;
-- 
2.17.1

On Thu, Mar 6, 2025 at 6:06 AM Prathamesh Shete <pshete@nvidia.com> wrote:

> Tegra devices have an 'sfsel' bit field that determines whether a pin
> operates in SFIO (Special Function I/O) or GPIO mode. Currently,
> tegra_pinctrl_gpio_disable_free() sets this bit when releasing a GPIO.
>
> However, tegra_pinctrl_set_mux() can be called independently in certain
> code paths where gpio_disable_free() is not invoked. In such cases, failing
> to set the SFIO mode could lead to incorrect pin configurations, resulting
> in functional issues for peripherals relying on SFIO.
>
> This patch ensures that whenever set_mux() is called, the SFIO mode is
> correctly set in the Mux Register if the 'sfsel' bit is present. This
> prevents situations where the pin remains in GPIO mode despite being
> configured for SFIO use.
>
> Fixes: 59b67585e242 ("pinctrl: add a driver for NVIDIA Tegra")
> Signed-off-by: Prathamesh Shete <pshete@nvidia.com>

Patch applied.

I can't tell how urgent this patch is so I have applied it for next
for the moment.

Yours,
Linus Walleij