staging: fbtft: Rectify GPIO handling

The infamous commit c440eee1 ("Staging: staging: fbtft: Switch to
the GPIO descriptor interface") broke GPIO handling completely.
It has already four commits to rectify and it seems not enough.
In order to fix the mess here we:

  1) Set default to "inactive" for all requested pins

  2) Fix CS#, RD#, and WR# pins polarity since it's active low
     and GPIO descriptor interface takes it into consideration
     from the Device Tree or ACPI

  3) Consolidate chip activation (CS# assertion) under default
     ->reset() callback

To summarize the expectations about polarity for GPIOs:

   RD#			Low
   WR#			Low
   CS#			Low
   RESET#		Low
   DC or RS		High
   RW			High
   Data	0 .. 15		High

See also Adafruit learning course [1] for the example of the schematics.

While at it, drop unneeded NULL checks, since GPIO API is tolerant to that.

[1]: https://learn.adafruit.com/adafruit-2-8-and-3-2-color-tft-touchscreen-breakout-v2/downloads

Fixes: 92e3e884 ("Staging: fbtft: Fix GPIO handling")
Fixes: b918d1c2 ("Staging: fbtft: Fix reset assertion when using gpio descriptor")
Fixes: dbc4f989 ("Staging: fbtft: Fix probing of gpio descriptor")
Fixes: c440eee1 ("Staging: fbtft: Switch to the gpio descriptor interface")
Cc: Jan Sebastian Götte <linux@jaseg.net>
Cc: Nishad Kamdar <nishadkamdar@gmail.com>
Reviewed-by: Phil Reid <preid@electromag.com.au>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20210503172114.27891-2-andriy.shevchenko@linux.intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/fbtft/fb_agm1264k-fl.c

@@ -84,9 +84,9 @@ static void reset(struct fbtft_par *par)
 
 	dev_dbg(par->info->device, "%s()\n", __func__);
 
-	gpiod_set_value(par->gpio.reset, 0);
-	udelay(20);
 	gpiod_set_value(par->gpio.reset, 1);
+	udelay(20);
+	gpiod_set_value(par->gpio.reset, 0);
 	mdelay(120);
 }
 
@@ -194,12 +194,12 @@ static void write_reg8_bus8(struct fbtft_par *par, int len, ...)
 	/* select chip */
 	if (*buf) {
 		/* cs1 */
-		gpiod_set_value(par->CS0, 1);
-		gpiod_set_value(par->CS1, 0);
-	} else {
-		/* cs0 */
 		gpiod_set_value(par->CS0, 0);
 		gpiod_set_value(par->CS1, 1);
+	} else {
+		/* cs0 */
+		gpiod_set_value(par->CS0, 1);
+		gpiod_set_value(par->CS1, 0);
 	}
 
 	gpiod_set_value(par->RS, 0); /* RS->0 (command mode) */
@@ -397,8 +397,8 @@ static int write_vmem(struct fbtft_par *par, size_t offset, size_t len)
 	}
 	kfree(convert_buf);
 
-	gpiod_set_value(par->CS0, 1);
-	gpiod_set_value(par->CS1, 1);
+	gpiod_set_value(par->CS0, 0);
+	gpiod_set_value(par->CS1, 0);
 
 	return ret;
 }
@@ -419,10 +419,10 @@ static int write(struct fbtft_par *par, void *buf, size_t len)
 		for (i = 0; i < 8; ++i)
 			gpiod_set_value(par->gpio.db[i], data & (1 << i));
 		/* set E */
-		gpiod_set_value(par->EPIN, 1);
+		gpiod_set_value(par->EPIN, 0);
 		udelay(5);
 		/* unset E - write */
-		gpiod_set_value(par->EPIN, 0);
+		gpiod_set_value(par->EPIN, 1);
 		udelay(1);
 	}
 

drivers/staging/fbtft/fb_bd663474.c

@@ -12,7 +12,6 @@
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/init.h>
-#include <linux/gpio/consumer.h>
 #include <linux/delay.h>
 
 #include "fbtft.h"
@@ -24,9 +23,6 @@
 
 static int init_display(struct fbtft_par *par)
 {
-	if (par->gpio.cs)
-		gpiod_set_value(par->gpio.cs, 0);  /* Activate chip */
-
 	par->fbtftops.reset(par);
 
 	/* Initialization sequence from Lib_UTFT */

drivers/staging/fbtft/fb_ili9163.c

@@ -11,7 +11,6 @@
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/init.h>
-#include <linux/gpio/consumer.h>
 #include <linux/delay.h>
 #include <video/mipi_display.h>
 
@@ -77,9 +76,6 @@ static int init_display(struct fbtft_par *par)
 {
 	par->fbtftops.reset(par);
 
-	if (par->gpio.cs)
-		gpiod_set_value(par->gpio.cs, 0);  /* Activate chip */
-
 	write_reg(par, MIPI_DCS_SOFT_RESET); /* software reset */
 	mdelay(500);
 	write_reg(par, MIPI_DCS_EXIT_SLEEP_MODE); /* exit sleep */

drivers/staging/fbtft/fb_ili9320.c

@@ -8,7 +8,6 @@
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/init.h>
-#include <linux/gpio/consumer.h>
 #include <linux/spi/spi.h>
 #include <linux/delay.h>
 

drivers/staging/fbtft/fb_ili9325.c

@@ -10,7 +10,6 @@
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/init.h>
-#include <linux/gpio/consumer.h>
 #include <linux/delay.h>
 
 #include "fbtft.h"
@@ -85,9 +84,6 @@ static int init_display(struct fbtft_par *par)
 {
 	par->fbtftops.reset(par);
 
-	if (par->gpio.cs)
-		gpiod_set_value(par->gpio.cs, 0);  /* Activate chip */
-
 	bt &= 0x07;
 	vc &= 0x07;
 	vrh &= 0x0f;

drivers/staging/fbtft/fb_ili9340.c

@@ -8,7 +8,6 @@
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/init.h>
-#include <linux/gpio/consumer.h>
 #include <linux/delay.h>
 #include <video/mipi_display.h>
 

drivers/staging/fbtft/fb_s6d1121.c

@@ -12,7 +12,6 @@
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/init.h>
-#include <linux/gpio/consumer.h>
 #include <linux/delay.h>
 
 #include "fbtft.h"
@@ -29,9 +28,6 @@ static int init_display(struct fbtft_par *par)
 {
 	par->fbtftops.reset(par);
 
-	if (par->gpio.cs)
-		gpiod_set_value(par->gpio.cs, 0);  /* Activate chip */
-
 	/* Initialization sequence from Lib_UTFT */
 
 	write_reg(par, 0x0011, 0x2004);

drivers/staging/fbtft/fb_sh1106.c

@@ -9,7 +9,6 @@
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/init.h>
-#include <linux/gpio/consumer.h>
 #include <linux/delay.h>
 
 #include "fbtft.h"

drivers/staging/fbtft/fb_ssd1289.c

@@ -10,7 +10,6 @@
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/init.h>
-#include <linux/gpio/consumer.h>
 
 #include "fbtft.h"
 
@@ -28,9 +27,6 @@ static int init_display(struct fbtft_par *par)
 {
 	par->fbtftops.reset(par);
 
-	if (par->gpio.cs)
-		gpiod_set_value(par->gpio.cs, 0);  /* Activate chip */
-
 	write_reg(par, 0x00, 0x0001);
 	write_reg(par, 0x03, 0xA8A4);
 	write_reg(par, 0x0C, 0x0000);

drivers/staging/fbtft/fb_ssd1325.c

@@ -35,8 +35,6 @@ static int init_display(struct fbtft_par *par)
 {
 	par->fbtftops.reset(par);
 
-	gpiod_set_value(par->gpio.cs, 0);
-
 	write_reg(par, 0xb3);
 	write_reg(par, 0xf0);
 	write_reg(par, 0xae);

drivers/staging/fbtft/fb_ssd1331.c

@@ -81,8 +81,7 @@ static void write_reg8_bus8(struct fbtft_par *par, int len, ...)
 	va_start(args, len);
 
 	*buf = (u8)va_arg(args, unsigned int);
-	if (par->gpio.dc)
-		gpiod_set_value(par->gpio.dc, 0);
+	gpiod_set_value(par->gpio.dc, 0);
 	ret = par->fbtftops.write(par, par->buf, sizeof(u8));
 	if (ret < 0) {
 		va_end(args);
@@ -104,8 +103,7 @@ static void write_reg8_bus8(struct fbtft_par *par, int len, ...)
 			return;
 		}
 	}
-	if (par->gpio.dc)
-		gpiod_set_value(par->gpio.dc, 1);
+	gpiod_set_value(par->gpio.dc, 1);
 	va_end(args);
 }
 

drivers/staging/fbtft/fb_ssd1351.c

@@ -2,7 +2,6 @@
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/init.h>
-#include <linux/gpio/consumer.h>
 #include <linux/spi/spi.h>
 #include <linux/delay.h>
 

drivers/staging/fbtft/fb_upd161704.c

@@ -12,7 +12,6 @@
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/init.h>
-#include <linux/gpio/consumer.h>
 #include <linux/delay.h>
 
 #include "fbtft.h"
@@ -26,9 +25,6 @@ static int init_display(struct fbtft_par *par)
 {
 	par->fbtftops.reset(par);
 
-	if (par->gpio.cs)
-		gpiod_set_value(par->gpio.cs, 0);  /* Activate chip */
-
 	/* Initialization sequence from Lib_UTFT */
 
 	/* register reset */

drivers/staging/fbtft/fb_watterott.c

@@ -8,7 +8,6 @@
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/init.h>
-#include <linux/gpio/consumer.h>
 #include <linux/delay.h>
 
 #include "fbtft.h"

drivers/staging/fbtft/fbtft-bus.c

@@ -135,8 +135,7 @@ int fbtft_write_vmem16_bus8(struct fbtft_par *par, size_t offset, size_t len)
 	remain = len / 2;
 	vmem16 = (u16 *)(par->info->screen_buffer + offset);
 
-	if (par->gpio.dc)
-		gpiod_set_value(par->gpio.dc, 1);
+	gpiod_set_value(par->gpio.dc, 1);
 
 	/* non buffered write */
 	if (!par->txbuf.buf)

drivers/staging/fbtft/fbtft-core.c

@@ -38,8 +38,7 @@ int fbtft_write_buf_dc(struct fbtft_par *par, void *buf, size_t len, int dc)
 {
 	int ret;
 
-	if (par->gpio.dc)
-		gpiod_set_value(par->gpio.dc, dc);
+	gpiod_set_value(par->gpio.dc, dc);
 
 	ret = par->fbtftops.write(par, buf, len);
 	if (ret < 0)
@@ -79,7 +78,7 @@ static int fbtft_request_one_gpio(struct fbtft_par *par,
 	int ret = 0;
 
 	*gpiop = devm_gpiod_get_index_optional(dev, name, index,
-					       GPIOD_OUT_HIGH);
+					       GPIOD_OUT_LOW);
 	if (IS_ERR(*gpiop)) {
 		ret = PTR_ERR(*gpiop);
 		dev_err(dev,
@@ -226,11 +225,15 @@ static void fbtft_reset(struct fbtft_par *par)
 {
 	if (!par->gpio.reset)
 		return;
+
 	fbtft_par_dbg(DEBUG_RESET, par, "%s()\n", __func__);
+
 	gpiod_set_value_cansleep(par->gpio.reset, 1);
 	usleep_range(20, 40);
 	gpiod_set_value_cansleep(par->gpio.reset, 0);
 	msleep(120);
+
+	gpiod_set_value_cansleep(par->gpio.cs, 1);  /* Activate chip */
 }
 
 static void fbtft_update_display(struct fbtft_par *par, unsigned int start_line,
@@ -922,8 +925,6 @@ static int fbtft_init_display_from_property(struct fbtft_par *par)
 		goto out_free;
 
 	par->fbtftops.reset(par);
-	if (par->gpio.cs)
-		gpiod_set_value(par->gpio.cs, 0);  /* Activate chip */
 
 	index = -1;
 	val = values[++index];
@@ -1018,8 +1019,6 @@ int fbtft_init_display(struct fbtft_par *par)
 	}
 
 	par->fbtftops.reset(par);
-	if (par->gpio.cs)
-		gpiod_set_value(par->gpio.cs, 0);  /* Activate chip */
 
 	i = 0;
 	while (i < FBTFT_MAX_INIT_SEQUENCE) {

drivers/staging/fbtft/fbtft-io.c

@@ -142,12 +142,12 @@ int fbtft_write_gpio8_wr(struct fbtft_par *par, void *buf, size_t len)
 		data = *(u8 *)buf;
 
 		/* Start writing by pulling down /WR */
-		gpiod_set_value(par->gpio.wr, 0);
+		gpiod_set_value(par->gpio.wr, 1);
 
 		/* Set data */
 #ifndef DO_NOT_OPTIMIZE_FBTFT_WRITE_GPIO
 		if (data == prev_data) {
-			gpiod_set_value(par->gpio.wr, 0); /* used as delay */
+			gpiod_set_value(par->gpio.wr, 1); /* used as delay */
 		} else {
 			for (i = 0; i < 8; i++) {
 				if ((data & 1) != (prev_data & 1))
@@ -165,7 +165,7 @@ int fbtft_write_gpio8_wr(struct fbtft_par *par, void *buf, size_t len)
 #endif
 
 		/* Pullup /WR */
-		gpiod_set_value(par->gpio.wr, 1);
+		gpiod_set_value(par->gpio.wr, 0);
 
 #ifndef DO_NOT_OPTIMIZE_FBTFT_WRITE_GPIO
 		prev_data = *(u8 *)buf;
@@ -192,12 +192,12 @@ int fbtft_write_gpio16_wr(struct fbtft_par *par, void *buf, size_t len)
 		data = *(u16 *)buf;
 
 		/* Start writing by pulling down /WR */
-		gpiod_set_value(par->gpio.wr, 0);
+		gpiod_set_value(par->gpio.wr, 1);
 
 		/* Set data */
 #ifndef DO_NOT_OPTIMIZE_FBTFT_WRITE_GPIO
 		if (data == prev_data) {
-			gpiod_set_value(par->gpio.wr, 0); /* used as delay */
+			gpiod_set_value(par->gpio.wr, 1); /* used as delay */
 		} else {
 			for (i = 0; i < 16; i++) {
 				if ((data & 1) != (prev_data & 1))
@@ -215,7 +215,7 @@ int fbtft_write_gpio16_wr(struct fbtft_par *par, void *buf, size_t len)
 #endif
 
 		/* Pullup /WR */
-		gpiod_set_value(par->gpio.wr, 1);
+		gpiod_set_value(par->gpio.wr, 0);
 
 #ifndef DO_NOT_OPTIMIZE_FBTFT_WRITE_GPIO
 		prev_data = *(u16 *)buf;