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linux/drivers/staging/fbtft
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Andy Shevchenko ec03c21043 staging: fbtft: Rectify GPIO handling 
The infamous commit c440eee1a7 ("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: 92e3e88488 ("Staging: fbtft: Fix GPIO handling")
Fixes: b918d1c270 ("Staging: fbtft: Fix reset assertion when using gpio descriptor")
Fixes: dbc4f989c8 ("Staging: fbtft: Fix probing of gpio descriptor")
Fixes: c440eee1a7 ("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>
2021-05-10 11:19:39 +02:00
..
fb_agm1264k-fl.c staging: fbtft: Rectify GPIO handling 2021-05-10 11:19:39 +02:00
fb_bd663474.c staging: fbtft: Rectify GPIO handling 2021-05-10 11:19:39 +02:00
fb_hx8340bn.c
fb_hx8347d.c
fb_hx8353d.c
fb_hx8357d.c
fb_hx8357d.h
fb_ili9163.c staging: fbtft: Rectify GPIO handling 2021-05-10 11:19:39 +02:00
fb_ili9320.c staging: fbtft: Rectify GPIO handling 2021-05-10 11:19:39 +02:00
fb_ili9325.c staging: fbtft: Rectify GPIO handling 2021-05-10 11:19:39 +02:00
fb_ili9340.c staging: fbtft: Rectify GPIO handling 2021-05-10 11:19:39 +02:00
fb_ili9341.c
fb_ili9481.c
fb_ili9486.c
fb_pcd8544.c
fb_ra8875.c
fb_s6d02a1.c
fb_s6d1121.c staging: fbtft: Rectify GPIO handling 2021-05-10 11:19:39 +02:00
fb_seps525.c drivers/staging/fbtft/fb_seps525: New driver for SEPS525 (Syncoam) LCD Controllers 2019-10-26 20:47:52 +02:00
fb_sh1106.c staging: fbtft: Rectify GPIO handling 2021-05-10 11:19:39 +02:00
fb_ssd1289.c staging: fbtft: Rectify GPIO handling 2021-05-10 11:19:39 +02:00
fb_ssd1305.c
fb_ssd1306.c
fb_ssd1325.c staging: fbtft: Rectify GPIO handling 2021-05-10 11:19:39 +02:00
fb_ssd1331.c staging: fbtft: Rectify GPIO handling 2021-05-10 11:19:39 +02:00
fb_ssd1351.c staging: fbtft: Rectify GPIO handling 2021-05-10 11:19:39 +02:00
fb_st7735r.c
fb_st7789v.c staging: fbtft: add tearing signal detect 2021-02-12 09:48:29 +01:00
fb_tinylcd.c
fb_tls8204.c
fb_uc1611.c staging: fbtft: Do not hardcode SPI CS polarity inversion 2019-12-10 10:56:53 +01:00
fb_uc1701.c
fb_upd161704.c staging: fbtft: Rectify GPIO handling 2021-05-10 11:19:39 +02:00
fb_watterott.c staging: fbtft: Rectify GPIO handling 2021-05-10 11:19:39 +02:00
fbtft-bus.c staging: fbtft: Rectify GPIO handling 2021-05-10 11:19:39 +02:00
fbtft-core.c staging: fbtft: Rectify GPIO handling 2021-05-10 11:19:39 +02:00
fbtft-io.c staging: fbtft: Rectify GPIO handling 2021-05-10 11:19:39 +02:00
fbtft-sysfs.c staging: fbtft: convert sysfs snprintf to sysfs_emit 2021-04-05 12:15:15 +02:00
fbtft.h staging: fbtft: Avoid potential precedence issues 2020-03-17 12:47:24 +01:00
internal.h
Kconfig staging: fbtft: Fix Kconfig indentation 2019-11-20 15:20:28 +01:00
Makefile drivers/staging/fbtft/fb_seps525: New driver for SEPS525 (Syncoam) LCD Controllers 2019-10-26 20:47:52 +02:00
README
TODO

README 

  FBTFT
=========

Linux Framebuffer drivers for small TFT LCD display modules.
The module 'fbtft' makes writing drivers for some of these displays very easy.

Development is done on a Raspberry Pi running the Raspbian "wheezy" distribution.

INSTALLATION
  Download kernel sources

  From Linux 3.15
    cd drivers/video/fbdev/fbtft
    git clone https://github.com/notro/fbtft.git

    Add to drivers/video/fbdev/Kconfig:   source "drivers/video/fbdev/fbtft/Kconfig"
    Add to drivers/video/fbdev/Makefile:  obj-y += fbtft/

  Before Linux 3.15
    cd drivers/video
    git clone https://github.com/notro/fbtft.git

    Add to drivers/video/Kconfig:   source "drivers/video/fbtft/Kconfig"
    Add to drivers/video/Makefile:  obj-y += fbtft/

  Enable driver(s) in menuconfig and build the kernel


See wiki for more information: https://github.com/notro/fbtft/wiki


Source: https://github.com/notro/fbtft/