pinctrl: mediatek: paris: Support generic PIN_CONFIG_DRIVE_STRENGTH_UA

Some of the MediaTek chips that utilize the Paris pinctrl driver library
support a lower drive strength (<= 1mA) than the standard drive strength
settings (2~16 mA) on certain pins. This was previously supported by the
custom MTK_PIN_CONFIG_DRV_ADV parameter along with the
"mediatek,drive-strength-adv" device tree property.

The drive strength values for this hardware are 125, 250, 500, and 1000 mA,
and can be readily described by the existing "drive-strength-microamp"
property, which then gets parsed by the generic pinconf library into the
parameter PIN_CONFIG_DRIVE_STRENGTH_UA.

Add support for PIN_CONFIG_DRIVE_STRENGTH_UA while keeping the old
custom parameter around for backward compatibility.

Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20220308100956.2750295-9-wenst@chromium.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

diff --git a/drivers/pinctrl/mediatek/pinctrl-paris.c b/drivers/pinctrl/mediatek/pinctrl-paris.c
index f8b7305..bed9862 100644 (file)
--- a/drivers/pinctrl/mediatek/pinctrl-paris.c
+++ b/drivers/pinctrl/mediatek/pinctrl-paris.c
@@ -48,6 +48,53 @@ static const char * const mtk_gpio_functions[] = {
        "func12", "func13", "func14", "func15",
 };
 
+/*
+ * This section supports converting to/from custom MTK_PIN_CONFIG_DRV_ADV
+ * and standard PIN_CONFIG_DRIVE_STRENGTH_UA pin configs.
+ *
+ * The custom value encodes three hardware bits as follows:
+ *
+ *   |           Bits           |
+ *   | 2 (E1) | 1 (E0) | 0 (EN) | drive strength (uA)
+ *   ------------------------------------------------
+ *   |    x   |    x   |    0   | disabled, use standard drive strength
+ *   -------------------------------------
+ *   |    0   |    0   |    1   |  125 uA
+ *   |    0   |    1   |    1   |  250 uA
+ *   |    1   |    0   |    1   |  500 uA
+ *   |    1   |    1   |    1   | 1000 uA
+ */
+static const int mtk_drv_adv_uA[] = { 125, 250, 500, 1000 };
+
+static int mtk_drv_adv_to_uA(int val)
+{
+       /* This should never happen. */
+       if (WARN_ON_ONCE(val < 0 || val > 7))
+               return -EINVAL;
+
+       /* Bit 0 simply enables this hardware part */
+       if (!(val & BIT(0)))
+               return -EINVAL;
+
+       return mtk_drv_adv_uA[(val >> 1)];
+}
+
+static int mtk_drv_uA_to_adv(int val)
+{
+       switch (val) {
+       case 125:
+               return 0x1;
+       case 250:
+               return 0x3;
+       case 500:
+               return 0x5;
+       case 1000:
+               return 0x7;
+       }
+
+       return -EINVAL;
+}
+
 static int mtk_pinmux_gpio_request_enable(struct pinctrl_dev *pctldev,
                                          struct pinctrl_gpio_range *range,
                                          unsigned int pin)
@@ -145,8 +192,35 @@ static int mtk_pinconf_get(struct pinctrl_dev *pctldev,
        case PIN_CONFIG_DRIVE_STRENGTH:
                if (!hw->soc->drive_get)
                        break;
+
+               if (hw->soc->adv_drive_get) {
+                       err = hw->soc->adv_drive_get(hw, desc, &ret);
+                       if (!err) {
+                               err = mtk_drv_adv_to_uA(ret);
+                               if (err > 0) {
+                                       /* PIN_CONFIG_DRIVE_STRENGTH_UA used */
+                                       err = -EINVAL;
+                                       break;
+                               }
+                       }
+               }
+
                err = hw->soc->drive_get(hw, desc, &ret);
                break;
+       case PIN_CONFIG_DRIVE_STRENGTH_UA:
+               if (!hw->soc->adv_drive_get)
+                       break;
+
+               err = hw->soc->adv_drive_get(hw, desc, &ret);
+               if (err)
+                       break;
+               err = mtk_drv_adv_to_uA(ret);
+               if (err < 0)
+                       break;
+
+               ret = err;
+               err = 0;
+               break;
        case MTK_PIN_CONFIG_TDSEL:
        case MTK_PIN_CONFIG_RDSEL:
                reg = (param == MTK_PIN_CONFIG_TDSEL) ?
@@ -252,6 +326,15 @@ static int mtk_pinconf_set(struct pinctrl_dev *pctldev, unsigned int pin,
                        break;
                err = hw->soc->drive_set(hw, desc, arg);
                break;
+       case PIN_CONFIG_DRIVE_STRENGTH_UA:
+               if (!hw->soc->adv_drive_set)
+                       break;
+
+               err = mtk_drv_uA_to_adv(arg);
+               if (err < 0)
+                       break;
+               err = hw->soc->adv_drive_set(hw, desc, err);
+               break;
        case MTK_PIN_CONFIG_TDSEL:
        case MTK_PIN_CONFIG_RDSEL:
                reg = (param == MTK_PIN_CONFIG_TDSEL) ?
@@ -720,6 +803,8 @@ static int mtk_pconf_group_set(struct pinctrl_dev *pctldev, unsigned group,
 {
        struct mtk_pinctrl *hw = pinctrl_dev_get_drvdata(pctldev);
        struct mtk_pinctrl_group *grp = &hw->groups[group];
+       bool drive_strength_uA_found = false;
+       bool adv_drve_strength_found = false;
        int i, ret;
 
        for (i = 0; i < num_configs; i++) {
@@ -728,8 +813,22 @@ static int mtk_pconf_group_set(struct pinctrl_dev *pctldev, unsigned group,
                                      pinconf_to_config_argument(configs[i]));
                if (ret < 0)
                        return ret;
+
+               if (pinconf_to_config_param(configs[i]) == PIN_CONFIG_DRIVE_STRENGTH_UA)
+                       drive_strength_uA_found = true;
+               if (pinconf_to_config_param(configs[i]) == MTK_PIN_CONFIG_DRV_ADV)
+                       adv_drve_strength_found = true;
        }
 
+       /*
+        * Disable advanced drive strength mode if drive-strength-microamp
+        * is not set. However, mediatek,drive-strength-adv takes precedence
+        * as its value can explicitly request the mode be enabled or not.
+        */
+       if (hw->soc->adv_drive_set && !drive_strength_uA_found &&
+           !adv_drve_strength_found)
+               hw->soc->adv_drive_set(hw, &hw->soc->pins[grp->pin], 0);
+
        return 0;
 }