staging: fbtft: Rectify GPIO handling

The infamous commit c440eee1a7a1 ("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: 92e3e884887c ("Staging: fbtft: Fix GPIO handling")
Fixes: b918d1c27066 ("Staging: fbtft: Fix reset assertion when using gpio descriptor")
Fixes: dbc4f989c878 ("Staging: fbtft: Fix probing of gpio descriptor")
Fixes: c440eee1a7a1 ("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.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 10 insertions, 10 deletions

diff --git a/drivers/staging/fbtft/fb_agm1264k-fl.c b/drivers/staging/fbtft/fb_agm1264k-fl.c
index eeeeec97ad27..b545c2ca80a4 100644
--- a/drivers/staging/fbtft/fb_agm1264k-fl.c
+++ b/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);
 	}