[PATCH 2/2] pinctrl: qcom: spmi-gpio: make direction changes exclusive

[Shawn Guo]

pmic_gpio_populate() seeds pad->input_enabled and pad->output_enabled from
the hardware MODE_CTL register, so a pad left in DIGITAL_INPUT or
DIGITAL_INPUT_OUTPUT mode by the bootloader starts out with the input
buffer enabled.  Neither direction callback clears the opposite buffer:
.direction_output() only packs PIN_CONFIG_LEVEL, which sets
output_enabled, and .direction_input() only packs PIN_CONFIG_INPUT_ENABLE,
which sets input_enabled.  Requesting either direction on such a pad
therefore programs MODE_DIGITAL_INPUT_OUTPUT rather than the requested
direction.

That silently breaks both directions.  After gpiod_direction_input() the
pad keeps driving the line, since the output buffer is never disabled.
And after gpiod_direction_output() pmic_gpio_get_direction() still reports
GPIO_LINE_DIRECTION_IN, because it cannot tell plain input from
input+output, which makes gpiolib consider the line an input while the
driver is driving it.  On a board where several regulator-fixed nodes
share one PMIC GPIO the shared GPIO proxy reads that direction back and
rejects every consumer after the first:

  reg-fixed-voltage regulator-wcn-core-vm-1p35: setup of GPIO (default) failed: -1
  reg-fixed-voltage regulator-wcn-core-vm-1p35: error -EPERM: can't get GPIO

Pack the opposite buffer's PIN_CONFIG_*_ENABLE along with the requested
direction so that the resulting MODE_CTL is DIGITAL_INPUT or
DIGITAL_OUTPUT, never both.  pmic_gpio_config_set() programs the registers
once after walking all configs, so this stays a single register write.

Pads that are genuinely bidirectional can still be described that way
through pinconf, which is the interface that has always been able to
express it; the gpiolib direction callbacks now mean what gpiolib says
they mean.

Assisted-by: LLM
Fixes: eadff3024472 ("pinctrl: Qualcomm SPMI PMIC GPIO pin controller driver")
Signed-off-by: Shawn Guo <shengchao.guo@xxxxxxxxxxxxxxxx>
---
 drivers/pinctrl/qcom/pinctrl-spmi-gpio.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/pinctrl/qcom/pinctrl-spmi-gpio.c b/drivers/pinctrl/qcom/pinctrl-spmi-gpio.c
index f6dc43e27b38..eb4431591331 100644
--- a/drivers/pinctrl/qcom/pinctrl-spmi-gpio.c
+++ b/drivers/pinctrl/qcom/pinctrl-spmi-gpio.c
@@ -741,22 +741,26 @@ static int pmic_gpio_get_direction(struct gpio_chip *chip, unsigned pin)
 static int pmic_gpio_direction_input(struct gpio_chip *chip, unsigned pin)
 {
 	struct pmic_gpio_state *state = gpiochip_get_data(chip);
-	unsigned long config;
+	unsigned long configs[2];
 
-	config = pinconf_to_config_packed(PIN_CONFIG_INPUT_ENABLE, 1);
+	configs[0] = pinconf_to_config_packed(PIN_CONFIG_OUTPUT_ENABLE, 0);
+	configs[1] = pinconf_to_config_packed(PIN_CONFIG_INPUT_ENABLE, 1);
 
-	return pmic_gpio_config_set(state->ctrl, pin, &config, 1);
+	return pmic_gpio_config_set(state->ctrl, pin, configs,
+				    ARRAY_SIZE(configs));
 }
 
 static int pmic_gpio_direction_output(struct gpio_chip *chip,
 				      unsigned pin, int val)
 {
 	struct pmic_gpio_state *state = gpiochip_get_data(chip);
-	unsigned long config;
+	unsigned long configs[2];
 
-	config = pinconf_to_config_packed(PIN_CONFIG_LEVEL, val);
+	configs[0] = pinconf_to_config_packed(PIN_CONFIG_INPUT_ENABLE, 0);
+	configs[1] = pinconf_to_config_packed(PIN_CONFIG_LEVEL, val);
 
-	return pmic_gpio_config_set(state->ctrl, pin, &config, 1);
+	return pmic_gpio_config_set(state->ctrl, pin, configs,
+				    ARRAY_SIZE(configs));
 }
 
 static int pmic_gpio_get(struct gpio_chip *chip, unsigned pin)
-- 
2.43.0