The LCDIF controller as present in i.MX28/i.MX6SX/i.MX8M Mini/Nano has
CRC_STAT register, which contains CRC32 of the frame as it was clocked
out of the DPI interface of the LCDIF. This is most likely meant as a
functional safety feature.
Unfortunately, there is zero documentation on how the CRC32 is calculated,
there is no documentation of the polynomial, the init value, nor on which
data is the checksum applied.
By applying brute-force on 8 pixel / 2 line frame, which is the minimum
size LCDIF would work with, it turns out the polynomial is CRC32_POLY_LE
0xedb88320 , init value is 0xffffffff , the input data are bitrev32()
of the entire frame and the resulting CRC has to be also bitrev32()ed.
Doing this calculation in kernel for each frame is unrealistic due to the
CPU demand, so attach the CRC collected from hardware to a frame instead.
The DRM subsystem already has an interface for this purpose and the CRC
can be accessed e.g. via debugfs:
"
$ echo auto > /sys/kernel/debug/dri/1/crtc-0/crc/control
$ cat /sys/kernel/debug/dri/1/crtc-0/crc/data
0x0000408c 0xa4e5cdd8
0x0000408d 0x72f537b4
"
The per-frame CRC can be used by userspace e.g. during automated testing,
to verify that whatever buffer was sent to be scanned out was actually
scanned out of the LCDIF correctly.
Acked-by: Lucas Stach <l.stach@pengutronix.de>
Acked-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Alexander Stein <alexander.stein@ew.tq-group.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Peng Fan <peng.fan@nxp.com>
Cc: Robby Cai <robby.cai@nxp.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Stefan Agner <stefan@agner.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20220429212313.305556-1-marex@denx.de
There is some sort of corner case behavior of the controller,
which could rarely be triggered at least on i.MX6SX connected
to 800x480 DPI panel and i.MX8MM connected to DPI->DSI->LVDS
bridged 1920x1080 panel (and likely on other setups too), where
the image on the panel shifts to the right and wraps around.
This happens either when the controller is enabled on boot or
even later during run time. The condition does not correct
itself automatically, i.e. the display image remains shifted.
It seems this problem is known and is due to sporadic underflows
of the LCDIF FIFO. While the LCDIF IP does have underflow/overflow
IRQs, neither of the IRQs trigger and neither IRQ status bit is
asserted when this condition occurs.
All known revisions of the LCDIF IP have CTRL1 RECOVER_ON_UNDERFLOW
bit, which is described in the reference manual since i.MX23 as
"
Set this bit to enable the LCDIF block to recover in the next
field/frame if there was an underflow in the current field/frame.
"
Enable this bit to mitigate the sporadic underflows.
Fixes: 45d59d7040 ("drm: Add new driver for MXSFB controller")
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Daniel Abrecht <public@danielabrecht.ch>
Cc: Emil Velikov <emil.l.velikov@gmail.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Stefan Agner <stefan@agner.ch>
Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210620224701.189289-1-marex@denx.de
Based on 3 normalized pattern(s):
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license as published by
the free software foundation either version 2 of the license or at
your option any later version this program is distributed in the
hope that it will be useful but without any warranty without even
the implied warranty of merchantability or fitness for a particular
purpose see the gnu general public license for more details
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license as published by
the free software foundation either version 2 of the license or at
your option any later version [author] [kishon] [vijay] [abraham]
[i] [kishon]@[ti] [com] this program is distributed in the hope that
it will be useful but without any warranty without even the implied
warranty of merchantability or fitness for a particular purpose see
the gnu general public license for more details
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license as published by
the free software foundation either version 2 of the license or at
your option any later version [author] [graeme] [gregory]
[gg]@[slimlogic] [co] [uk] [author] [kishon] [vijay] [abraham] [i]
[kishon]@[ti] [com] [based] [on] [twl6030]_[usb] [c] [author] [hema]
[hk] [hemahk]@[ti] [com] this program is distributed in the hope
that it will be useful but without any warranty without even the
implied warranty of merchantability or fitness for a particular
purpose see the gnu general public license for more details
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-or-later
has been chosen to replace the boilerplate/reference in 1105 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Richard Fontana <rfontana@redhat.com>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190527070033.202006027@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The LCD bus width does not need to align with the pixel format. The
LCDIF controller automatically converts between pixel formats and
bus width by padding or dropping LSBs.
The DRM subsystem has the notion of bus_format which allows to
determine what bus_formats are supported by the display. Choose the
first available or fallback to 24 bit if none are available.
Signed-off-by: Stefan Agner <stefan@agner.ch>
Acked-by: Marek Vasut <marex@denx.de>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Add new driver for the MXSFB controller found in i.MX23/28/6SX .
The MXSFB controller is a simple framebuffer controller with one
parallel LCD output. Unlike the MXSFB fbdev driver that is used
on these systems now, this driver uses the DRM/KMS framework.
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Fabio Estevam <fabio.estevam@nxp.com>
Cc: Shawn Guo <shawnguo@kernel.org>
