Re: [PATCH v9 2/2] drm/bridge: Add NWL MIPI DSI host controller support

[Guido Günther]

Hi Sam,

On Wed, Mar 18, 2020 at 10:46:39PM +0100, Sam Ravnborg wrote:
> Hi Guido.
> 
> Impressive and very detailed changelog in intro mail - nice.
> 
> On Wed, Mar 18, 2020 at 04:09:08PM +0100, Guido Günther wrote:
> > This adds initial support for the NWL MIPI DSI Host controller found on
> > i.MX8 SoCs.
> > 
> > It adds support for the i.MX8MQ but the same IP can be found on
> > e.g. the i.MX8QXP.
> > 
> > It has been tested on the Librem 5 devkit using mxsfb.
> > 
> > Signed-off-by: Guido Günther <agx@xxxxxxxxxxx>
> > Co-developed-by: Robert Chiras <robert.chiras@xxxxxxx>
> > Signed-off-by: Robert Chiras <robert.chiras@xxxxxxx>
> > Tested-by: Robert Chiras <robert.chiras@xxxxxxx>
> > Tested-by: Martin Kepplinger <martin.kepplinger@xxxxxxx>
> > ---
> >  drivers/gpu/drm/bridge/Kconfig   |   16 +
> >  drivers/gpu/drm/bridge/Makefile  |    3 +
> >  drivers/gpu/drm/bridge/nwl-dsi.c | 1213 ++++++++++++++++++++++++++++++
> >  drivers/gpu/drm/bridge/nwl-dsi.h |  144 ++++
> >  4 files changed, 1376 insertions(+)
> >  create mode 100644 drivers/gpu/drm/bridge/nwl-dsi.c
> >  create mode 100644 drivers/gpu/drm/bridge/nwl-dsi.h
> > 
> > diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> > index 8397bf72d2f3..d41d93d24f16 100644
> > --- a/drivers/gpu/drm/bridge/Kconfig
> > +++ b/drivers/gpu/drm/bridge/Kconfig
> > @@ -55,6 +55,22 @@ config DRM_MEGACHIPS_STDPXXXX_GE_B850V3_FW
> >  	  to DP++. This is used with the i.MX6 imx-ldb
> >  	  driver. You are likely to say N here.
> >  
> > +config DRM_NWL_MIPI_DSI
> > +	tristate "Northwest Logic MIPI DSI Host controller"
> > +	depends on DRM
> > +	depends on COMMON_CLK
> > +	depends on OF && HAS_IOMEM
> > +	select DRM_KMS_HELPER
> > +	select DRM_MIPI_DSI
> > +	select DRM_PANEL_BRIDGE
> > +	select GENERIC_PHY_MIPI_DPHY
> > +	select MFD_SYSCON
> > +	select MULTIPLEXER
> > +	select REGMAP_MMIO
> > +	help
> > +	  This enables the Northwest Logic MIPI DSI Host controller as
> > +	  for example found on NXP's i.MX8 Processors.
> > +
> >  config DRM_NXP_PTN3460
> >  	tristate "NXP PTN3460 DP/LVDS bridge"
> >  	depends on OF
> > diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
> > index 1eb5376c5d68..98581b3128a3 100644
> > --- a/drivers/gpu/drm/bridge/Makefile
> > +++ b/drivers/gpu/drm/bridge/Makefile
> > @@ -15,6 +15,9 @@ obj-$(CONFIG_DRM_TOSHIBA_TC358767) += tc358767.o
> >  obj-$(CONFIG_DRM_I2C_ADV7511) += adv7511/
> >  obj-$(CONFIG_DRM_TI_SN65DSI86) += ti-sn65dsi86.o
> >  obj-$(CONFIG_DRM_TI_TFP410) += ti-tfp410.o
> > +obj-$(CONFIG_DRM_NWL_MIPI_DSI) += nwl-dsi.o
> >  
> >  obj-y += analogix/
> >  obj-y += synopsys/
> > +
> > +header-test-y += nwl-dsi.h
> Sorry - but header-test-y support was ripped out of the kernel again.
> So this line has no longer any effect.

Missed that removal, dropped.

> > +
> > +static void nwl_dsi_bridge_enable(struct drm_bridge *bridge)
> > +{
> > +	struct nwl_dsi *dsi = bridge_to_dsi(bridge);
> > +	int ret;
> > +
> > +	/* Step 5 from DSI reset-out instructions */
> > +	ret = reset_control_deassert(dsi->rst_dpi);
> > +	if (ret < 0)
> > +		DRM_DEV_ERROR(dsi->dev, "Failed to deassert DPI: %d\n", ret);
> I picked this for a general comment.
> 
>     We have drm_err(drm, "...", ...) which is preferred over DRM_XXX
>     They require a drm_device * that may not be available everywhere.
> 
> IMO not a showstopper, but should be trivial to fix (if adrm_device * is
> a avaiable).

We don't do a drm_dev_alloc so no drm device here afaik tell.

> 
> > +}
> > +
> > +static int nwl_dsi_bridge_attach(struct drm_bridge *bridge)
> > +{
> > +	struct nwl_dsi *dsi = bridge_to_dsi(bridge);
> > +	struct drm_bridge *panel_bridge;
> > +	struct drm_panel *panel;
> > +	int ret;
> 
> This function now takes a flags argument.
> In other words - the driver will not build when applied
> to drm-misc-next.

Fixed by rebasing on next-20200317. I'll send a new version after
letting this sit for a moment. It'd be so cool to get this queued up so
we get a working display stack on the imx8mq.

Cheers,
 -- Guido

> 
> > +
> > +	ret = drm_of_find_panel_or_bridge(dsi->dev->of_node, 1, 0, &panel,
> > +					  &panel_bridge);
> > +	if (ret)
> > +		return ret;
> > +
> > +	if (panel) {
> > +		panel_bridge = drm_panel_bridge_add(panel);
> > +		if (IS_ERR(panel_bridge))
> > +			return PTR_ERR(panel_bridge);
> > +	}
> > +	dsi->panel_bridge = panel_bridge;
> > +
> > +	if (!dsi->panel_bridge)
> > +		return -EPROBE_DEFER;
> > +
> > +	return drm_bridge_attach(bridge->encoder, dsi->panel_bridge, bridge);
> > +}
> 
> 	Sam
>