This patch adds a drm bridge driver for i.MX8qm/qxp display pixel link.
The pixel link forms a standard asynchronous linkage between
pixel sources(display controller or camera module) and pixel
consumers(imaging or displays).  It consists of two distinct
functions, a pixel transfer function and a control interface.

Reviewed-by: Robert Foss <robert.f...@linaro.org>
Tested-by: Marcel Ziswiler <marcel.ziswi...@toradex.com> # Colibri iMX8X, 
LT170410-2WHC, LP156WF1
Signed-off-by: Liu Ying <victor....@nxp.com>
---
Robert, I keep your R-b tag from v5. Let me know if you want me to drop it, as
v7 contains a fix for checkpatch complaints.
Marcel, as the fix is trivial, I add your T-b tag. Let me know if you want me
to drop it.

v6->v7:
* Fix 'Alignment should match open parenthesis' complaints from
  'checkpatch.pl --strict'.
* Add Marcel's T-b tag.

v5->v6:
* No change.

v4->v5:
* Make a comment occupy a line. (Robert)
* Add Robert's R-b tag.

v3->v4:
* No change.

v2->v3:
* Drop two macros which help define functions and define them directly.
* Properly disable all pixel link controls to POR value by calling
  imx8qxp_pixel_link_disable_all_controls() from
  imx8qxp_pixel_link_bridge_probe().

v1->v2:
* Rewrite the function to find the next bridge by properly using OF APIs
  and dropping unnecessary DT validation. (Rob)

 drivers/gpu/drm/bridge/imx/Kconfig              |   8 +
 drivers/gpu/drm/bridge/imx/Makefile             |   1 +
 drivers/gpu/drm/bridge/imx/imx8qxp-pixel-link.c | 429 ++++++++++++++++++++++++
 3 files changed, 438 insertions(+)
 create mode 100644 drivers/gpu/drm/bridge/imx/imx8qxp-pixel-link.c

diff --git a/drivers/gpu/drm/bridge/imx/Kconfig 
b/drivers/gpu/drm/bridge/imx/Kconfig
index f1c91b6..4d1f027 100644
--- a/drivers/gpu/drm/bridge/imx/Kconfig
+++ b/drivers/gpu/drm/bridge/imx/Kconfig
@@ -6,3 +6,11 @@ config DRM_IMX8QXP_PIXEL_COMBINER
        help
          Choose this to enable pixel combiner found in
          Freescale i.MX8qm/qxp processors.
+
+config DRM_IMX8QXP_PIXEL_LINK
+       tristate "Freescale i.MX8QM/QXP display pixel link"
+       depends on OF
+       select DRM_KMS_HELPER
+       help
+         Choose this to enable display pixel link found in
+         Freescale i.MX8qm/qxp processors.
diff --git a/drivers/gpu/drm/bridge/imx/Makefile 
b/drivers/gpu/drm/bridge/imx/Makefile
index 7d7c8d6..c15469f 100644
--- a/drivers/gpu/drm/bridge/imx/Makefile
+++ b/drivers/gpu/drm/bridge/imx/Makefile
@@ -1 +1,2 @@
 obj-$(CONFIG_DRM_IMX8QXP_PIXEL_COMBINER) += imx8qxp-pixel-combiner.o
+obj-$(CONFIG_DRM_IMX8QXP_PIXEL_LINK) += imx8qxp-pixel-link.o
diff --git a/drivers/gpu/drm/bridge/imx/imx8qxp-pixel-link.c 
b/drivers/gpu/drm/bridge/imx/imx8qxp-pixel-link.c
new file mode 100644
index 00000000..52b9b96
--- /dev/null
+++ b/drivers/gpu/drm/bridge/imx/imx8qxp-pixel-link.c
@@ -0,0 +1,429 @@
+// SPDX-License-Identifier: GPL-2.0+
+
+/*
+ * Copyright 2020 NXP
+ */
+
+#include <linux/firmware/imx/svc/misc.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_graph.h>
+#include <linux/platform_device.h>
+
+#include <drm/drm_atomic_state_helper.h>
+#include <drm/drm_bridge.h>
+#include <drm/drm_print.h>
+
+#include <dt-bindings/firmware/imx/rsrc.h>
+
+#define DRIVER_NAME            "imx8qxp-display-pixel-link"
+#define PL_MAX_MST_ADDR                3
+#define PL_MAX_NEXT_BRIDGES    2
+
+struct imx8qxp_pixel_link {
+       struct drm_bridge bridge;
+       struct drm_bridge *next_bridge;
+       struct device *dev;
+       struct imx_sc_ipc *ipc_handle;
+       int id;
+       int stream_id;
+       int dc_id;
+       u32 sink_rsc;
+       u32 mst_addr;
+       u8 mst_addr_ctrl;
+       u8 mst_en_ctrl;
+       u8 mst_vld_ctrl;
+       u8 sync_ctrl;
+};
+
+static void imx8qxp_pixel_link_enable_mst_en(struct imx8qxp_pixel_link *pl)
+{
+       int ret;
+
+       ret = imx_sc_misc_set_control(pl->ipc_handle, pl->sink_rsc,
+                                     pl->mst_en_ctrl, true);
+       if (ret)
+               DRM_DEV_ERROR(pl->dev,
+                             "failed to enable DC%d stream%d pixel link 
mst_en: %d\n",
+                             pl->dc_id, pl->stream_id, ret);
+}
+
+static void imx8qxp_pixel_link_enable_mst_vld(struct imx8qxp_pixel_link *pl)
+{
+       int ret;
+
+       ret = imx_sc_misc_set_control(pl->ipc_handle, pl->sink_rsc,
+                                     pl->mst_vld_ctrl, true);
+       if (ret)
+               DRM_DEV_ERROR(pl->dev,
+                             "failed to enable DC%d stream%d pixel link 
mst_vld: %d\n",
+                             pl->dc_id, pl->stream_id, ret);
+}
+
+static void imx8qxp_pixel_link_enable_sync(struct imx8qxp_pixel_link *pl)
+{
+       int ret;
+
+       ret = imx_sc_misc_set_control(pl->ipc_handle, pl->sink_rsc,
+                                     pl->sync_ctrl, true);
+       if (ret)
+               DRM_DEV_ERROR(pl->dev,
+                             "failed to enable DC%d stream%d pixel link sync: 
%d\n",
+                             pl->dc_id, pl->stream_id, ret);
+}
+
+static int imx8qxp_pixel_link_disable_mst_en(struct imx8qxp_pixel_link *pl)
+{
+       int ret;
+
+       ret = imx_sc_misc_set_control(pl->ipc_handle, pl->sink_rsc,
+                                     pl->mst_en_ctrl, false);
+       if (ret)
+               DRM_DEV_ERROR(pl->dev,
+                             "failed to disable DC%d stream%d pixel link 
mst_en: %d\n",
+                             pl->dc_id, pl->stream_id, ret);
+
+       return ret;
+}
+
+static int imx8qxp_pixel_link_disable_mst_vld(struct imx8qxp_pixel_link *pl)
+{
+       int ret;
+
+       ret = imx_sc_misc_set_control(pl->ipc_handle, pl->sink_rsc,
+                                     pl->mst_vld_ctrl, false);
+       if (ret)
+               DRM_DEV_ERROR(pl->dev,
+                             "failed to disable DC%d stream%d pixel link 
mst_vld: %d\n",
+                             pl->dc_id, pl->stream_id, ret);
+
+       return ret;
+}
+
+static int imx8qxp_pixel_link_disable_sync(struct imx8qxp_pixel_link *pl)
+{
+       int ret;
+
+       ret = imx_sc_misc_set_control(pl->ipc_handle, pl->sink_rsc,
+                                     pl->sync_ctrl, false);
+       if (ret)
+               DRM_DEV_ERROR(pl->dev,
+                             "failed to disable DC%d stream%d pixel link sync: 
%d\n",
+                             pl->dc_id, pl->stream_id, ret);
+
+       return ret;
+}
+
+static void imx8qxp_pixel_link_set_mst_addr(struct imx8qxp_pixel_link *pl)
+{
+       int ret;
+
+       ret = imx_sc_misc_set_control(pl->ipc_handle,
+                                     pl->sink_rsc, pl->mst_addr_ctrl,
+                                     pl->mst_addr);
+       if (ret)
+               DRM_DEV_ERROR(pl->dev,
+                             "failed to set DC%d stream%d pixel link mst 
addr(%u): %d\n",
+                             pl->dc_id, pl->stream_id, pl->mst_addr, ret);
+}
+
+static int imx8qxp_pixel_link_bridge_attach(struct drm_bridge *bridge,
+                                           enum drm_bridge_attach_flags flags)
+{
+       struct imx8qxp_pixel_link *pl = bridge->driver_private;
+
+       if (!(flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR)) {
+               DRM_DEV_ERROR(pl->dev,
+                             "do not support creating a drm_connector\n");
+               return -EINVAL;
+       }
+
+       if (!bridge->encoder) {
+               DRM_DEV_ERROR(pl->dev, "missing encoder\n");
+               return -ENODEV;
+       }
+
+       return drm_bridge_attach(bridge->encoder,
+                                pl->next_bridge, bridge,
+                                DRM_BRIDGE_ATTACH_NO_CONNECTOR);
+}
+
+static void
+imx8qxp_pixel_link_bridge_mode_set(struct drm_bridge *bridge,
+                                  const struct drm_display_mode *mode,
+                                  const struct drm_display_mode *adjusted_mode)
+{
+       struct imx8qxp_pixel_link *pl = bridge->driver_private;
+
+       imx8qxp_pixel_link_set_mst_addr(pl);
+}
+
+static void
+imx8qxp_pixel_link_bridge_atomic_enable(struct drm_bridge *bridge,
+                                       struct drm_bridge_state 
*old_bridge_state)
+{
+       struct imx8qxp_pixel_link *pl = bridge->driver_private;
+
+       imx8qxp_pixel_link_enable_mst_en(pl);
+       imx8qxp_pixel_link_enable_mst_vld(pl);
+       imx8qxp_pixel_link_enable_sync(pl);
+}
+
+static void
+imx8qxp_pixel_link_bridge_atomic_disable(struct drm_bridge *bridge,
+                                        struct drm_bridge_state 
*old_bridge_state)
+{
+       struct imx8qxp_pixel_link *pl = bridge->driver_private;
+
+       imx8qxp_pixel_link_disable_mst_en(pl);
+       imx8qxp_pixel_link_disable_mst_vld(pl);
+       imx8qxp_pixel_link_disable_sync(pl);
+}
+
+static const u32 imx8qxp_pixel_link_bus_output_fmts[] = {
+       MEDIA_BUS_FMT_RGB888_1X36_CPADLO,
+       MEDIA_BUS_FMT_RGB666_1X36_CPADLO,
+};
+
+static bool imx8qxp_pixel_link_bus_output_fmt_supported(u32 fmt)
+{
+       int i;
+
+       for (i = 0; i < ARRAY_SIZE(imx8qxp_pixel_link_bus_output_fmts); i++) {
+               if (imx8qxp_pixel_link_bus_output_fmts[i] == fmt)
+                       return true;
+       }
+
+       return false;
+}
+
+static u32 *
+imx8qxp_pixel_link_bridge_atomic_get_input_bus_fmts(struct drm_bridge *bridge,
+                                                   struct drm_bridge_state 
*bridge_state,
+                                                   struct drm_crtc_state 
*crtc_state,
+                                                   struct drm_connector_state 
*conn_state,
+                                                   u32 output_fmt,
+                                                   unsigned int 
*num_input_fmts)
+{
+       u32 *input_fmts;
+
+       if (!imx8qxp_pixel_link_bus_output_fmt_supported(output_fmt))
+               return NULL;
+
+       *num_input_fmts = 1;
+
+       input_fmts = kmalloc(sizeof(*input_fmts), GFP_KERNEL);
+       if (!input_fmts)
+               return NULL;
+
+       input_fmts[0] = output_fmt;
+
+       return input_fmts;
+}
+
+static u32 *
+imx8qxp_pixel_link_bridge_atomic_get_output_bus_fmts(struct drm_bridge *bridge,
+                                                    struct drm_bridge_state 
*bridge_state,
+                                                    struct drm_crtc_state 
*crtc_state,
+                                                    struct drm_connector_state 
*conn_state,
+                                                    unsigned int 
*num_output_fmts)
+{
+       *num_output_fmts = ARRAY_SIZE(imx8qxp_pixel_link_bus_output_fmts);
+       return kmemdup(imx8qxp_pixel_link_bus_output_fmts,
+                       sizeof(imx8qxp_pixel_link_bus_output_fmts), GFP_KERNEL);
+}
+
+static const struct drm_bridge_funcs imx8qxp_pixel_link_bridge_funcs = {
+       .atomic_duplicate_state = drm_atomic_helper_bridge_duplicate_state,
+       .atomic_destroy_state   = drm_atomic_helper_bridge_destroy_state,
+       .atomic_reset           = drm_atomic_helper_bridge_reset,
+       .attach                 = imx8qxp_pixel_link_bridge_attach,
+       .mode_set               = imx8qxp_pixel_link_bridge_mode_set,
+       .atomic_enable          = imx8qxp_pixel_link_bridge_atomic_enable,
+       .atomic_disable         = imx8qxp_pixel_link_bridge_atomic_disable,
+       .atomic_get_input_bus_fmts =
+                       imx8qxp_pixel_link_bridge_atomic_get_input_bus_fmts,
+       .atomic_get_output_bus_fmts =
+                       imx8qxp_pixel_link_bridge_atomic_get_output_bus_fmts,
+};
+
+static int imx8qxp_pixel_link_disable_all_controls(struct imx8qxp_pixel_link 
*pl)
+{
+       int ret;
+
+       ret = imx8qxp_pixel_link_disable_mst_en(pl);
+       if (ret)
+               return ret;
+
+       ret = imx8qxp_pixel_link_disable_mst_vld(pl);
+       if (ret)
+               return ret;
+
+       return imx8qxp_pixel_link_disable_sync(pl);
+}
+
+static struct drm_bridge *
+imx8qxp_pixel_link_find_next_bridge(struct imx8qxp_pixel_link *pl)
+{
+       struct device_node *np = pl->dev->of_node;
+       struct device_node *port, *remote;
+       struct drm_bridge *next_bridge[PL_MAX_NEXT_BRIDGES];
+       u32 port_id;
+       bool found_port = false;
+       int reg, ep_cnt = 0;
+       /* select the first next bridge by default */
+       int bridge_sel = 0;
+
+       for (port_id = 1; port_id <= PL_MAX_MST_ADDR + 1; port_id++) {
+               port = of_graph_get_port_by_id(np, port_id);
+               if (!port)
+                       continue;
+
+               if (of_device_is_available(port)) {
+                       found_port = true;
+                       of_node_put(port);
+                       break;
+               }
+
+               of_node_put(port);
+       }
+
+       if (!found_port) {
+               DRM_DEV_ERROR(pl->dev, "no available output port\n");
+               return ERR_PTR(-ENODEV);
+       }
+
+       for (reg = 0; reg < PL_MAX_NEXT_BRIDGES; reg++) {
+               remote = of_graph_get_remote_node(np, port_id, reg);
+               if (!remote)
+                       continue;
+
+               if (!of_device_is_available(remote->parent)) {
+                       DRM_DEV_DEBUG(pl->dev,
+                                     "port%u endpoint%u remote parent is not 
available\n",
+                                     port_id, reg);
+                       of_node_put(remote);
+                       continue;
+               }
+
+               next_bridge[ep_cnt] = of_drm_find_bridge(remote);
+               if (!next_bridge[ep_cnt]) {
+                       of_node_put(remote);
+                       return ERR_PTR(-EPROBE_DEFER);
+               }
+
+               /* specially select the next bridge with companion PXL2DPI */
+               if (of_find_property(remote, "fsl,companion-pxl2dpi", NULL))
+                       bridge_sel = ep_cnt;
+
+               ep_cnt++;
+
+               of_node_put(remote);
+       }
+
+       pl->mst_addr = port_id - 1;
+
+       return next_bridge[bridge_sel];
+}
+
+static int imx8qxp_pixel_link_bridge_probe(struct platform_device *pdev)
+{
+       struct imx8qxp_pixel_link *pl;
+       struct device *dev = &pdev->dev;
+       struct device_node *np = dev->of_node;
+       int ret;
+
+       pl = devm_kzalloc(dev, sizeof(*pl), GFP_KERNEL);
+       if (!pl)
+               return -ENOMEM;
+
+       ret = imx_scu_get_handle(&pl->ipc_handle);
+       if (ret) {
+               if (ret != -EPROBE_DEFER)
+                       DRM_DEV_ERROR(dev, "failed to get SCU ipc handle: %d\n",
+                                     ret);
+               return ret;
+       }
+
+       pl->id = of_alias_get_id(np, "dc_pl");
+       if (pl->id < 0) {
+               DRM_DEV_ERROR(dev,
+                             "failed to get pixel link node alias id: %d\n",
+                             pl->id);
+               return pl->id;
+       }
+
+       pl->dev = dev;
+
+       pl->dc_id = pl->id / 2;
+       pl->stream_id = pl->id % 2;
+
+       pl->sink_rsc = pl->dc_id ? IMX_SC_R_DC_1 : IMX_SC_R_DC_0;
+
+       if (pl->stream_id == 0) {
+               pl->mst_addr_ctrl = IMX_SC_C_PXL_LINK_MST1_ADDR;
+               pl->mst_en_ctrl   = IMX_SC_C_PXL_LINK_MST1_ENB;
+               pl->mst_vld_ctrl  = IMX_SC_C_PXL_LINK_MST1_VLD;
+               pl->sync_ctrl     = IMX_SC_C_SYNC_CTRL0;
+       } else {
+               pl->mst_addr_ctrl = IMX_SC_C_PXL_LINK_MST2_ADDR;
+               pl->mst_en_ctrl   = IMX_SC_C_PXL_LINK_MST2_ENB;
+               pl->mst_vld_ctrl  = IMX_SC_C_PXL_LINK_MST2_VLD;
+               pl->sync_ctrl     = IMX_SC_C_SYNC_CTRL1;
+       }
+
+       /* disable all controls to POR default */
+       ret = imx8qxp_pixel_link_disable_all_controls(pl);
+       if (ret)
+               return ret;
+
+       pl->next_bridge = imx8qxp_pixel_link_find_next_bridge(pl);
+       if (IS_ERR(pl->next_bridge)) {
+               ret = PTR_ERR(pl->next_bridge);
+               if (ret != -EPROBE_DEFER)
+                       DRM_DEV_ERROR(dev, "failed to find next bridge: %d\n",
+                                     ret);
+               return ret;
+       }
+
+       platform_set_drvdata(pdev, pl);
+
+       pl->bridge.driver_private = pl;
+       pl->bridge.funcs = &imx8qxp_pixel_link_bridge_funcs;
+       pl->bridge.of_node = np;
+
+       drm_bridge_add(&pl->bridge);
+
+       return ret;
+}
+
+static int imx8qxp_pixel_link_bridge_remove(struct platform_device *pdev)
+{
+       struct imx8qxp_pixel_link *pl = platform_get_drvdata(pdev);
+
+       drm_bridge_remove(&pl->bridge);
+
+       return 0;
+}
+
+static const struct of_device_id imx8qxp_pixel_link_dt_ids[] = {
+       { .compatible = "fsl,imx8qm-dc-pixel-link", },
+       { .compatible = "fsl,imx8qxp-dc-pixel-link", },
+       { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, imx8qxp_pixel_link_dt_ids);
+
+static struct platform_driver imx8qxp_pixel_link_bridge_driver = {
+       .probe  = imx8qxp_pixel_link_bridge_probe,
+       .remove = imx8qxp_pixel_link_bridge_remove,
+       .driver = {
+               .of_match_table = imx8qxp_pixel_link_dt_ids,
+               .name = DRIVER_NAME,
+       },
+};
+module_platform_driver(imx8qxp_pixel_link_bridge_driver);
+
+MODULE_DESCRIPTION("i.MX8QXP/QM display pixel link bridge driver");
+MODULE_AUTHOR("Liu Ying <victor....@nxp.com>");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:" DRIVER_NAME);
-- 
2.7.4

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