Re: [PATCH v4 10/14] drm/bridge: imx: Add LDB driver helper support

[Liu Ying <victor.liu@nxp.com>]

Hi Robert,

On Tue, 2021-03-02 at 15:22 +0100, Robert Foss wrote:
> Hey Liu,
> 
> Thanks for submitting this patch.

Thanks for reviewing this patch.

> 
> On Thu, 18 Feb 2021 at 04:59, Liu Ying <victor.liu@nxp.com> wrote:
> > This patch adds a helper to support LDB drm bridge drivers for
> > i.MX SoCs.  Helper functions exported from this driver should
> > implement common logics for all LDB modules embedded in i.MX SoCs.
> > 
> > Signed-off-by: Liu Ying <victor.liu@nxp.com>
> > ---
> > v3->v4:
> > * No change.
> > 
> > v2->v3:
> > * Call syscon_node_to_regmap() to get regmap instead of
> >   syscon_regmap_lookup_by_phandle().
> > 
> > v1->v2:
> > * No change.
> > 
> >  drivers/gpu/drm/bridge/imx/Kconfig          |   8 +
> >  drivers/gpu/drm/bridge/imx/Makefile         |   1 +
> >  drivers/gpu/drm/bridge/imx/imx-ldb-helper.c | 248 ++++++++++++++++++++++++++++
> >  include/drm/bridge/imx_ldb_helper.h         |  98 +++++++++++
> >  4 files changed, 355 insertions(+)
> >  create mode 100644 drivers/gpu/drm/bridge/imx/imx-ldb-helper.c
> >  create mode 100644 include/drm/bridge/imx_ldb_helper.h
> > 
> > diff --git a/drivers/gpu/drm/bridge/imx/Kconfig b/drivers/gpu/drm/bridge/imx/Kconfig
> > index 1ea1ce7..23e24fd 100644
> > --- a/drivers/gpu/drm/bridge/imx/Kconfig
> > +++ b/drivers/gpu/drm/bridge/imx/Kconfig
> > @@ -1,3 +1,11 @@
> > +config DRM_IMX_LVDS_BRIDGE_HELPER
> > +       tristate "Freescale i.MX LVDS display bridge helper"
> > +       depends on OF
> > +       select DRM_PANEL_BRIDGE
> > +       help
> > +         Helper to support Freescale i.MX LVDS Display Bridge(LDB).
> > +         This bridge is embedded in a SoC.
> > +
> >  config DRM_IMX8QXP_PIXEL_COMBINER
> >         tristate "Freescale i.MX8QM/QXP pixel combiner"
> >         depends on OF
> > diff --git a/drivers/gpu/drm/bridge/imx/Makefile b/drivers/gpu/drm/bridge/imx/Makefile
> > index e74dd64..902b703 100644
> > --- a/drivers/gpu/drm/bridge/imx/Makefile
> > +++ b/drivers/gpu/drm/bridge/imx/Makefile
> > @@ -1,3 +1,4 @@
> > +obj-$(CONFIG_DRM_IMX_LVDS_BRIDGE_HELPER) += imx-ldb-helper.o
> >  obj-$(CONFIG_DRM_IMX8QXP_PIXEL_COMBINER) += imx8qxp-pixel-combiner.o
> >  obj-$(CONFIG_DRM_IMX8QXP_PIXEL_LINK) += imx8qxp-pixel-link.o
> >  obj-$(CONFIG_DRM_IMX8QXP_PIXEL_LINK_TO_DPI) += imx8qxp-pxl2dpi.o
> > diff --git a/drivers/gpu/drm/bridge/imx/imx-ldb-helper.c b/drivers/gpu/drm/bridge/imx/imx-ldb-helper.c
> > new file mode 100644
> > index 00000000..94d7f9e
> > --- /dev/null
> > +++ b/drivers/gpu/drm/bridge/imx/imx-ldb-helper.c
> > @@ -0,0 +1,248 @@
> > +// SPDX-License-Identifier: GPL-2.0+
> > +/*
> > + * Copyright (C) 2012 Sascha Hauer, Pengutronix
> > + * Copyright 2019,2020 NXP
> > + */
> > +
> > +#include <linux/mfd/syscon.h>
> > +#include <linux/module.h>
> > +#include <linux/of.h>
> > +#include <linux/regmap.h>
> > +
> > +#include <drm/bridge/imx_ldb_helper.h>
> > +#include <drm/drm_of.h>
> > +#include <drm/drm_panel.h>
> > +#include <drm/drm_print.h>
> > +
> > +bool ldb_channel_is_single_link(struct ldb_channel *ldb_ch)
> > +{
> > +       return ldb_ch->link_type == LDB_CH_SINGLE_LINK;
> > +}
> > +EXPORT_SYMBOL_GPL(ldb_channel_is_single_link);
> > +
> > +bool ldb_channel_is_split_link(struct ldb_channel *ldb_ch)
> > +{
> > +       return ldb_ch->link_type == LDB_CH_DUAL_LINK_EVEN_ODD_PIXELS ||
> > +              ldb_ch->link_type == LDB_CH_DUAL_LINK_ODD_EVEN_PIXELS;
> > +}
> > +EXPORT_SYMBOL_GPL(ldb_channel_is_split_link);
> > +
> > +int ldb_bridge_atomic_check_helper(struct drm_bridge *bridge,
> > +                                  struct drm_bridge_state *bridge_state,
> > +                                  struct drm_crtc_state *crtc_state,
> > +                                  struct drm_connector_state *conn_state)
> > +{
> > +       struct ldb_channel *ldb_ch = bridge->driver_private;
> > +
> > +       ldb_ch->in_bus_format = bridge_state->input_bus_cfg.format;
> > +       ldb_ch->out_bus_format = bridge_state->output_bus_cfg.format;
> > +
> > +       return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(ldb_bridge_atomic_check_helper);
> > +
> > +void ldb_bridge_mode_set_helper(struct drm_bridge *bridge,
> > +                               const struct drm_display_mode *mode,
> > +                               const struct drm_display_mode *adjusted_mode)
> > +{
> > +       struct ldb_channel *ldb_ch = bridge->driver_private;
> > +       struct ldb *ldb = ldb_ch->ldb;
> > +       bool is_split = ldb_channel_is_split_link(ldb_ch);
> > +
> > +       if (is_split)
> > +               ldb->ldb_ctrl |= LDB_SPLIT_MODE_EN;
> > +
> > +       switch (ldb_ch->out_bus_format) {
> > +       case MEDIA_BUS_FMT_RGB666_1X7X3_SPWG:
> > +               break;
> > +       case MEDIA_BUS_FMT_RGB888_1X7X4_SPWG:
> > +               if (ldb_ch->chno == 0 || is_split)
> > +                       ldb->ldb_ctrl |= LDB_DATA_WIDTH_CH0_24;
> > +               if (ldb_ch->chno == 1 || is_split)
> > +                       ldb->ldb_ctrl |= LDB_DATA_WIDTH_CH1_24;
> > +               break;
> > +       case MEDIA_BUS_FMT_RGB888_1X7X4_JEIDA:
> > +               if (ldb_ch->chno == 0 || is_split)
> > +                       ldb->ldb_ctrl |= LDB_DATA_WIDTH_CH0_24 |
> > +                                        LDB_BIT_MAP_CH0_JEIDA;
> > +               if (ldb_ch->chno == 1 || is_split)
> > +                       ldb->ldb_ctrl |= LDB_DATA_WIDTH_CH1_24 |
> > +                                        LDB_BIT_MAP_CH1_JEIDA;
> > +               break;
> > +       }
> > +}
> > +EXPORT_SYMBOL_GPL(ldb_bridge_mode_set_helper);
> > +
> > +void ldb_bridge_enable_helper(struct drm_bridge *bridge)
> > +{
> > +       struct ldb_channel *ldb_ch = bridge->driver_private;
> > +       struct ldb *ldb = ldb_ch->ldb;
> > +
> > +       /*
> > +        * Platform specific bridge drivers should set ldb_ctrl properly
> > +        * for the enablement, so just write the ctrl_reg here.
> > +        */
> > +       regmap_write(ldb->regmap, ldb->ctrl_reg, ldb->ldb_ctrl);
> > +}
> > +EXPORT_SYMBOL_GPL(ldb_bridge_enable_helper);
> > +
> > +void ldb_bridge_disable_helper(struct drm_bridge *bridge)
> > +{
> > +       struct ldb_channel *ldb_ch = bridge->driver_private;
> > +       struct ldb *ldb = ldb_ch->ldb;
> > +       bool is_split = ldb_channel_is_split_link(ldb_ch);
> > +
> > +       if (ldb_ch->chno == 0 || is_split)
> > +               ldb->ldb_ctrl &= ~LDB_CH0_MODE_EN_MASK;
> > +       if (ldb_ch->chno == 1 || is_split)
> > +               ldb->ldb_ctrl &= ~LDB_CH1_MODE_EN_MASK;
> > +
> > +       regmap_write(ldb->regmap, ldb->ctrl_reg, ldb->ldb_ctrl);
> > +}
> > +EXPORT_SYMBOL_GPL(ldb_bridge_disable_helper);
> > +
> > +int ldb_bridge_attach_helper(struct drm_bridge *bridge,
> > +                            enum drm_bridge_attach_flags flags)
> > +{
> > +       struct ldb_channel *ldb_ch = bridge->driver_private;
> > +       struct ldb *ldb = ldb_ch->ldb;
> > +
> > +       if (!(flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR)) {
> > +               DRM_DEV_ERROR(ldb->dev,
> > +                             "do not support creating a drm_connector\n");
> > +               return -EINVAL;
> > +       }
> > +
> > +       if (!bridge->encoder) {
> > +               DRM_DEV_ERROR(ldb->dev, "missing encoder\n");
> > +               return -ENODEV;
> > +       }
> > +
> > +       return drm_bridge_attach(bridge->encoder,
> > +                               ldb_ch->next_bridge, bridge,
> > +                               DRM_BRIDGE_ATTACH_NO_CONNECTOR);
> > +}
> > +EXPORT_SYMBOL_GPL(ldb_bridge_attach_helper);
> > +
> > +int ldb_init_helper(struct ldb *ldb)
> > +{
> > +       struct device *dev = ldb->dev;
> > +       struct device_node *np = dev->of_node;
> > +       struct device_node *child;
> > +       int ret;
> > +       u32 i;
> > +
> > +       ldb->regmap = syscon_node_to_regmap(np->parent);
> > +       if (IS_ERR(ldb->regmap)) {
> > +               ret = PTR_ERR(ldb->regmap);
> > +               if (ret != -EPROBE_DEFER)
> > +                       DRM_DEV_ERROR(dev, "failed to get regmap: %d\n", ret);
> > +               return ret;
> > +       }
> > +
> > +       for_each_available_child_of_node(np, child) {
> > +               struct ldb_channel *ldb_ch;
> > +
> > +               ret = of_property_read_u32(child, "reg", &i);
> > +               if (ret || i > MAX_LDB_CHAN_NUM - 1) {
> > +                       ret = -EINVAL;
> > +                       DRM_DEV_ERROR(dev,
> > +                                     "invalid channel node address: %u\n", i);
> > +                       of_node_put(child);
> > +                       return ret;
> > +               }
> > +
> > +               ldb_ch = ldb->channel[i];
> > +               ldb_ch->ldb = ldb;
> > +               ldb_ch->chno = i;
> > +               ldb_ch->is_available = true;
> > +               ldb_ch->np = child;
> > +
> > +               ldb->available_ch_cnt++;
> > +       }
> > +
> > +       return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(ldb_init_helper);
> > +
> > +int ldb_find_next_bridge_helper(struct ldb *ldb)
> > +{
> > +       struct device *dev = ldb->dev;
> > +       struct ldb_channel *ldb_ch;
> > +       int ret, i;
> > +
> > +       for (i = 0; i < MAX_LDB_CHAN_NUM; i++) {
> > +               ldb_ch = ldb->channel[i];
> > +
> > +               if (!ldb_ch->is_available)
> > +                       continue;
> > +
> > +               ret = drm_of_find_panel_or_bridge(ldb_ch->np, 1, 0,
> > +                                                 &ldb_ch->panel,
> > +                                                 &ldb_ch->next_bridge);
> > +               if (ret) {
> > +                       if (ret != -EPROBE_DEFER)
> > +                               DRM_DEV_ERROR(dev,
> > +                                       "failed to find panel or bridge: %d\n",
> > +                                                                       ret);
> > +                       return ret;
> > +               }
> > +
> > +               if (ldb_ch->panel) {
> > +                       ldb_ch->next_bridge = devm_drm_panel_bridge_add(dev,
> > +                                                               ldb_ch->panel);
> > +                       if (IS_ERR(ldb_ch->next_bridge)) {
> > +                               ret = PTR_ERR(ldb_ch->next_bridge);
> > +                               DRM_DEV_ERROR(dev,
> > +                                       "failed to add panel bridge: %d\n",
> > +                                                                       ret);
> > +                               return ret;
> > +                       }
> > +               }
> > +       }
> > +
> > +       return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(ldb_find_next_bridge_helper);
> > +
> > +void ldb_add_bridge_helper(struct ldb *ldb,
> > +                          const struct drm_bridge_funcs *bridge_funcs)
> > +{
> > +       struct ldb_channel *ldb_ch;
> > +       int i;
> > +
> > +       for (i = 0; i < MAX_LDB_CHAN_NUM; i++) {
> > +               ldb_ch = ldb->channel[i];
> > +
> > +               if (!ldb_ch->is_available)
> > +                       continue;
> > +
> > +               ldb_ch->bridge.driver_private = ldb_ch;
> > +               ldb_ch->bridge.funcs = bridge_funcs;
> > +               ldb_ch->bridge.of_node = ldb_ch->np;
> > +
> > +               drm_bridge_add(&ldb_ch->bridge);
> > +       }
> > +}
> > +EXPORT_SYMBOL_GPL(ldb_add_bridge_helper);
> > +
> > +void ldb_remove_bridge_helper(struct ldb *ldb)
> > +{
> > +       struct ldb_channel *ldb_ch;
> > +       int i;
> > +
> > +       for (i = 0; i < MAX_LDB_CHAN_NUM; i++) {
> > +               ldb_ch = ldb->channel[i];
> > +
> > +               if (!ldb_ch->is_available)
> > +                       continue;
> > +
> > +               drm_bridge_remove(&ldb_ch->bridge);
> > +       }
> > +}
> > +EXPORT_SYMBOL_GPL(ldb_remove_bridge_helper);
> > +
> > +MODULE_DESCRIPTION("Freescale i.MX LVDS Display Bridge driver helper");
> > +MODULE_AUTHOR("Liu Ying <victor.liu@nxp.com>");
> > +MODULE_LICENSE("GPL v2");
> > +MODULE_ALIAS("platform:imx-ldb-helper");
> 
> I'm not entirely sure why this set of helper functions should be a
> module. It's not a driver, but rather a toolbox for the LDB driver,
> which is fine, but there is no situation I can see where this module
> would be unloaded and the LDB driver would be loaded.

I can see drivers/gpu/drm/drm_mipi_dbi.c is also a module and
essentially provides helpers to MIPI DBI drivers, but it is not a
driver.  I don't see this imx-ldb-helper can be anything else other
than a module.

Or, do you mean that imx-ldb-helper should be only built-in?

> 
> > diff --git a/include/drm/bridge/imx_ldb_helper.h b/include/drm/bridge/imx_ldb_helper.h
> > new file mode 100644
> > index 00000000..2a7ba97
> > --- /dev/null
> > +++ b/include/drm/bridge/imx_ldb_helper.h
> 
> This header is specific to this driver, and I would expect it to not
> be useful to other drivers. Additionally the filename has a different
> format than the .c file it corresponds to. I would change the name and
> path to "drivers/gpu/drm/bridge/imx/imx-ldb-helper.h".

The i.MX53/6qdl LDB driver(drivers/gpu/drm/imx/imx-ldb.c) can
potentially use this header, but it's a DRM encoder driver.
So, maybe, it's a good idea to move this header to the 'drivers' folder
and rename it to 'imx-ldb-helper.h' ofc.  If no objections, I'll do as
what you're suggesting here in the next version.

Regards,
Liu Ying

> 
> > @@ -0,0 +1,98 @@
> > +/* SPDX-License-Identifier: GPL-2.0+ */
> > +
> > +/*
> > + * Copyright 2019,2020 NXP
> > + */
> > +
> > +#ifndef __FSL_IMX_LDB__
> > +#define __FSL_IMX_LDB__
> > +
> > +#include <linux/device.h>
> > +#include <linux/kernel.h>
> > +#include <linux/of.h>
> > +#include <linux/regmap.h>
> > +
> > +#include <drm/drm_atomic.h>
> > +#include <drm/drm_bridge.h>
> > +#include <drm/drm_device.h>
> > +#include <drm/drm_encoder.h>
> > +#include <drm/drm_modeset_helper_vtables.h>
> > +#include <drm/drm_panel.h>
> > +
> > +#define LDB_CH0_MODE_EN_TO_DI0         (1 << 0)
> > +#define LDB_CH0_MODE_EN_TO_DI1         (3 << 0)
> > +#define LDB_CH0_MODE_EN_MASK           (3 << 0)
> > +#define LDB_CH1_MODE_EN_TO_DI0         (1 << 2)
> > +#define LDB_CH1_MODE_EN_TO_DI1         (3 << 2)
> > +#define LDB_CH1_MODE_EN_MASK           (3 << 2)
> > +#define LDB_SPLIT_MODE_EN              (1 << 4)
> > +#define LDB_DATA_WIDTH_CH0_24          (1 << 5)
> > +#define LDB_BIT_MAP_CH0_JEIDA          (1 << 6)
> > +#define LDB_DATA_WIDTH_CH1_24          (1 << 7)
> > +#define LDB_BIT_MAP_CH1_JEIDA          (1 << 8)
> > +#define LDB_DI0_VS_POL_ACT_LOW         (1 << 9)
> > +#define LDB_DI1_VS_POL_ACT_LOW         (1 << 10)
> > +
> > +#define MAX_LDB_CHAN_NUM               2
> > +
> > +enum ldb_channel_link_type {
> > +       LDB_CH_SINGLE_LINK,
> > +       LDB_CH_DUAL_LINK_EVEN_ODD_PIXELS,
> > +       LDB_CH_DUAL_LINK_ODD_EVEN_PIXELS,
> > +};
> > +
> > +struct ldb;
> > +
> > +struct ldb_channel {
> > +       struct ldb *ldb;
> > +       struct drm_bridge bridge;
> > +       struct drm_panel *panel;
> > +       struct drm_bridge *next_bridge;
> > +       struct device_node *np;
> > +       u32 chno;
> > +       bool is_available;
> > +       u32 in_bus_format;
> > +       u32 out_bus_format;
> > +       enum ldb_channel_link_type link_type;
> > +};
> > +
> > +struct ldb {
> > +       struct regmap *regmap;
> > +       struct device *dev;
> > +       struct ldb_channel *channel[MAX_LDB_CHAN_NUM];
> > +       unsigned int ctrl_reg;
> > +       u32 ldb_ctrl;
> > +       unsigned int available_ch_cnt;
> > +};
> > +
> > +#define bridge_to_ldb_ch(b)    container_of(b, struct ldb_channel, bridge)
> > +
> > +bool ldb_channel_is_single_link(struct ldb_channel *ldb_ch);
> > +bool ldb_channel_is_split_link(struct ldb_channel *ldb_ch);
> > +
> > +int ldb_bridge_atomic_check_helper(struct drm_bridge *bridge,
> > +                                  struct drm_bridge_state *bridge_state,
> > +                                  struct drm_crtc_state *crtc_state,
> > +                                  struct drm_connector_state *conn_state);
> > +
> > +void ldb_bridge_mode_set_helper(struct drm_bridge *bridge,
> > +                               const struct drm_display_mode *mode,
> > +                               const struct drm_display_mode *adjusted_mode);
> > +
> > +void ldb_bridge_enable_helper(struct drm_bridge *bridge);
> > +
> > +void ldb_bridge_disable_helper(struct drm_bridge *bridge);
> > +
> > +int ldb_bridge_attach_helper(struct drm_bridge *bridge,
> > +                            enum drm_bridge_attach_flags flags);
> > +
> > +int ldb_init_helper(struct ldb *ldb);
> > +
> > +int ldb_find_next_bridge_helper(struct ldb *ldb);
> > +
> > +void ldb_add_bridge_helper(struct ldb *ldb,
> > +                          const struct drm_bridge_funcs *bridge_funcs);
> > +
> > +void ldb_remove_bridge_helper(struct ldb *ldb);
> > +
> > +#endif /* __FSL_IMX_LDB__ */
> > --
> > 2.7.4
> > 


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