[v5,0/5] drm/tiny: Add MIPI DBI compatible SPI driver

Hi,

This patchset adds a driver that will work with most MIPI DBI compatible
SPI panels out there.

It can replace the SPI interface support in these drivers:

$ grep -lr MIPI_DCS drivers/staging/fbtft/ | grep -v "-" | uniq | sort
drivers/staging/fbtft/fb_hx8340bn.c
drivers/staging/fbtft/fb_hx8353d.c
drivers/staging/fbtft/fb_hx8357d.c
drivers/staging/fbtft/fb_ili9163.c
drivers/staging/fbtft/fb_ili9340.c
drivers/staging/fbtft/fb_ili9341.c
drivers/staging/fbtft/fb_ili9481.c
drivers/staging/fbtft/fb_ili9486.c
drivers/staging/fbtft/fb_s6d02a1.c
drivers/staging/fbtft/fb_st7735r.c
drivers/staging/fbtft/fb_st7789v.c
drivers/staging/fbtft/fb_tinylcd.c

Note that the MIPI DBI parallel interface supported by fbtft does not
yet exist in DRM.

Maxime gave[1] a good overview of the situation with these displays and
proposed to make a driver that works with all MIPI DBI compatible
controllers and use a firmware file to provide the controller setup for
a particular panel.

Changes since version 4:
- Add sainsmart18 to compatible items (Rob)
- Expand write-only description (Sam)
- kconfig: s/DRM_KMS_CMA_HELPER/DRM_GEM_CMA_HELPER/ (Sam)
- kconfig: Add select VIDEOMODE_HELPERS (Sam)
- kconfig: Add wiki url in the description (Sam)
- Split out and use of_get_drm_panel_display_mode()(Sam)
- Only use the first compatible to look for a firmware file since the
  binding mandates 2 compatibles.
- Make having a firmware file mandatory so we can print an error
  message if it's missing to improve the user experience. It's very
  unlikely that a controller doesn't need to be initialized and if
  it doesn't, it's possible to have a firmware file containing only
  a DCS NOP.

See wiki[2] for a script to make command firmware files.

Noralf.

[1] https://lore.kernel.org/dri-devel/20211129093946.xhp22mvdut3m67sc@houat/
[2] https://github.com/notro/panel-mipi-dbi/wiki


Noralf Trønnes (5):
  dt-bindings: display: add bindings for MIPI DBI compatible SPI panels
  drm/modes: Remove trailing whitespace
  drm/modes: Add of_get_drm_panel_display_mode()
  drm/mipi-dbi: Add driver_private member to struct mipi_dbi_dev
  drm/tiny: Add MIPI DBI compatible SPI driver

 .../display/panel/panel-mipi-dbi-spi.yaml     | 127 ++++++
 MAINTAINERS                                   |   8 +
 drivers/gpu/drm/drm_modes.c                   |  51 ++-
 drivers/gpu/drm/tiny/Kconfig                  |  15 +
 drivers/gpu/drm/tiny/Makefile                 |   1 +
 drivers/gpu/drm/tiny/panel-mipi-dbi.c         | 398 ++++++++++++++++++
 include/drm/drm_mipi_dbi.h                    |   8 +
 include/drm/drm_modes.h                       |   8 +
 8 files changed, 615 insertions(+), 1 deletion(-)
 create mode 100644 Documentation/devicetree/bindings/display/panel/panel-mipi-dbi-spi.yaml
 create mode 100644 drivers/gpu/drm/tiny/panel-mipi-dbi.c

On Thu, Feb 24, 2022 at 04:27:05PM +0100, Noralf Trønnes wrote:
> Remove trailing whitespace from a comment.
> 
> Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
> ---
>  drivers/gpu/drm/drm_modes.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_modes.c b/drivers/gpu/drm/drm_modes.c
> index 96b13e36293c..77a4c8dd0bb8 100644
> --- a/drivers/gpu/drm/drm_modes.c
> +++ b/drivers/gpu/drm/drm_modes.c
> @@ -127,7 +127,7 @@ EXPORT_SYMBOL(drm_mode_probed_add);
>   * according to the hdisplay, vdisplay, vrefresh.
>   * It is based from the VESA(TM) Coordinated Video Timing Generator by
>   * Graham Loveridge April 9, 2003 available at
> - * http://www.elo.utfsm.cl/~elo212/docs/CVTd6r1.xls 
> + * http://www.elo.utfsm.cl/~elo212/docs/CVTd6r1.xls
>   *
>   * And it is copied from xf86CVTmode in xserver/hw/xfree86/modes/xf86cvt.c.
>   * What I have done is to translate it by using integer calculation.
> -- 
> 2.33.0

On Thu, Feb 24, 2022 at 04:27:06PM +0100, Noralf Trønnes wrote:
> Add a function to get a drm_display_mode from a panel-timing
> device tree subnode.

Thanks for implementing this!

> 
> Suggested-by: Sam Ravnborg <sam@ravnborg.org>
> Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>

Hi Noralf,

On Thu, Feb 24, 2022 at 04:27:08PM +0100, Noralf Trønnes wrote:
> Add a driver that will work with most MIPI DBI compatible SPI panels.
> This avoids adding a driver for every new MIPI DBI compatible controller
> that is to be used by Linux. The 'compatible' Device Tree property with
> a '.bin' suffix will be used to load a firmware file that contains the
> controller configuration.
> 
> Example (driver will load sainsmart18.bin):
> 
> display@0 {
> 	compatible = "sainsmart18", "panel-mipi-dbi-spi";
> ...
> };
> 
> v5:
> - kconfig: s/DRM_KMS_CMA_HELPER/DRM_GEM_CMA_HELPER/ (Sam)
> - kconfig: Add select VIDEOMODE_HELPERS (Sam)
> - kconfig: Add wiki url in the description (Sam)
> - Split out and use of_get_drm_panel_display_mode()(Sam)
> - Only use the first compatible to look for a firmware file since the
>   binding mandates 2 compatibles.
> - Make having a firmware file mandatory so we can print an error
>   message if it's missing to improve the user experience. It's very
>   unlikely that a controller doesn't need to be initialized and if
>   it doesn't, it's possible to have a firmware file containing only
>   a DCS NOP.
> 
> v4:
> - Move driver to drm/tiny where the other drivers of its kind are located.
>   The driver module will not be shared with a future DPI driver after all.
> 
> v3:
> - Move properties to DT (Maxime)
> - The MIPI DPI spec has optional support for DPI where the controller is
>   configured over DBI. Rework the command functions so they can be moved
>   to drm_mipi_dbi and shared with a future panel-mipi-dpi-spi driver
> 
> v2:
> - Drop model property and use compatible instead (Rob)
> - Add wiki entry in MAINTAINERS
> 
> Acked-by: Maxime Ripard <maxime@cerno.tech>
> Signed-off-by: Noralf Trønnes <noralf@tronnes.org>

Looks good.

Reviewed-by: Sam Ravnborg <sam@ravnborg.org>