linux-kernel - [PATCH 3/3] gpio: mmio: Use new flag BGPIOF_NO

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Message-Id: <20230126-gpio-mmio-fix-v1-3-8a20ce0e8275@ncr.com>
Date:   Thu, 26 Jan 2023 10:17:24 +0000
From:   Niall Leonard via B4 Submission Endpoint 
        <devnull+nl250060.ncr.com@...nel.org>
To:     Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
Cc:     linux-gpio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, Niall Leonard <nl250060@....com>
Subject: [PATCH 3/3] gpio: mmio: Use new flag BGPIOF_NO_INPUT

From: Niall Leonard <nl250060@....com>

Use the existing shadow data register 'bgpio_data' to allow
the last written value to be returned by the read operation
when BGPIOF_NO_INPUT flag is set.

Signed-off-by: Niall Leonard <nl250060@....com>
---
 drivers/gpio/gpio-mmio.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/drivers/gpio/gpio-mmio.c b/drivers/gpio/gpio-mmio.c
index d9dff3dc92ae..7125bd8caaa4 100644
--- a/drivers/gpio/gpio-mmio.c
+++ b/drivers/gpio/gpio-mmio.c
@@ -164,6 +164,11 @@ static int bgpio_get_set_multiple(struct gpio_chip *gc, unsigned long *mask,
 	return 0;
 }
 
+static int bgpio_get_shadow(struct gpio_chip *gc, unsigned int gpio)
+{
+	return !!(gc->bgpio_data & bgpio_line2mask(gc, gpio));
+}
+
 static int bgpio_get(struct gpio_chip *gc, unsigned int gpio)
 {
 	return !!(gc->read_reg(gc->reg_dat) & bgpio_line2mask(gc, gpio));
@@ -526,7 +531,10 @@ static int bgpio_setup_io(struct gpio_chip *gc,
 		 * reading each line individually in that fringe case.
 		 */
 	} else {
-		gc->get = bgpio_get;
+		if (flags & BGPIOF_NO_INPUT)
+			gc->get = bgpio_get_shadow;
+		else
+			gc->get = bgpio_get;
 		if (gc->be_bits)
 			gc->get_multiple = bgpio_get_multiple_be;
 		else
@@ -630,7 +638,11 @@ int bgpio_init(struct gpio_chip *gc, struct device *dev,
 	if (ret)
 		return ret;
 
-	gc->bgpio_data = gc->read_reg(gc->reg_dat);
+	if (flags & BGPIOF_NO_INPUT)
+		gc->bgpio_data = 0;
+	else
+		gc->bgpio_data = gc->read_reg(gc->reg_dat);
+
 	if (gc->set == bgpio_set_set &&
 			!(flags & BGPIOF_UNREADABLE_REG_SET))
 		gc->bgpio_data = gc->read_reg(gc->reg_set);
@@ -711,6 +723,9 @@ static struct bgpio_pdata *bgpio_parse_dt(struct platform_device *pdev,
 	if (of_property_read_bool(pdev->dev.of_node, "no-output"))
 		*flags |= BGPIOF_NO_OUTPUT;
 
+	if (of_property_read_bool(pdev->dev.of_node, "no-input"))
+		*flags |= BGPIOF_NO_INPUT;
+
 	return pdata;
 }
 #else

-- 
2.34.1