[PATCH 1/2 v16] Documentation: bridge: Add documentation for ps8640 DT properties

[PATCH 1/2 v16] Documentation: bridge: Add documentation for ps8640 DT properties

[Jitao Shi]

Add documentation for DT properties supported by
ps8640 DSI-eDP converter.

Signed-off-by: Jitao Shi <jitao.shi@mediatek.com>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
---
Changes since v15:
 - No change.

Changes since v14:
 - change mode-sel-gpios as optional.
---
 .../devicetree/bindings/display/bridge/ps8640.txt  |   44 ++++++++++++++++++++
 1 file changed, 44 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/display/bridge/ps8640.txt

diff --git a/Documentation/devicetree/bindings/display/bridge/ps8640.txt b/Documentation/devicetree/bindings/display/bridge/ps8640.txt
new file mode 100644
index 0000000..7b13f92
--- /dev/null
+++ b/Documentation/devicetree/bindings/display/bridge/ps8640.txt
@@ -0,0 +1,44 @@
+ps8640-bridge bindings
+
+Required properties:
+	- compatible: "parade,ps8640"
+	- reg: first page address of the bridge.
+	- sleep-gpios: OF device-tree gpio specification for PD pin.
+	- reset-gpios: OF device-tree gpio specification for reset pin.
+	- vdd12-supply: OF device-tree regulator specification for 1.2V power.
+	- vdd33-supply: OF device-tree regulator specification for 3.3V power.
+	- ports: The device node can contain video interface port nodes per
+		 the video-interfaces bind[1]. For port@0,set the reg = <0> as
+		 ps8640 dsi in and port@1,set the reg = <1> as ps8640 eDP out.
+
+Optional properties:
+	- mode-sel-gpios: OF device-tree gpio specification for mode-sel pin.
+[1]: Documentation/devicetree/bindings/media/video-interfaces.txt
+
+Example:
+	edp-bridge@18 {
+		compatible = "parade,ps8640";
+		reg = <0x18>;
+		sleep-gpios = <&pio 116 GPIO_ACTIVE_LOW>;
+		reset-gpios = <&pio 115 GPIO_ACTIVE_LOW>;
+		mode-sel-gpios = <&pio 92 GPIO_ACTIVE_HIGH>;
+		vdd12-supply = <&ps8640_fixed_1v2>;
+		vdd33-supply = <&mt6397_vgp2_reg>;
+
+		ports {
+			#address-cells = <1>;
+			#size-cells = <0>;
+			port@0 {
+				reg = <0>;
+				ps8640_in: endpoint {
+					remote-endpoint = <&dsi0_out>;
+				};
+			};
+			port@1 {
+				reg = <1>;
+				ps8640_out: endpoint {
+					remote-endpoint = <&panel_in>;
+				};
+			};
+		};
+	};
-- 
1.7.9.5

[PATCH 2/2 v16] drm/bridge: Add I2C based driver for ps8640 bridge

[Jitao Shi]

This patch adds drm_bridge driver for parade DSI to eDP bridge chip.

Signed-off-by: Jitao Shi <jitao.shi@mediatek.com>
Reviewed-by: Daniel Kurtz <djkurtz@chromium.org>
---
Changes since v15:
 - Drop drm_connector_(un)register calls from parade ps8640.
   The main DRM driver mtk_drm_drv now calls
   drm_connector_register_all() after drm_dev_register() in the
   mtk_drm_bind() function. That function should iterate over all
   connectors and call drm_connector_register() for each of them.
   So, remove drm_connector_(un)register calls from parade ps8640.

Changes since v14:
 - update copyright info.
 - change bridge_to_ps8640 and connector_to_ps8640 to inline function.
 - fix some coding style.
 - use sizeof as array counter.
 - use drm_get_edid when read edid.
 - add mutex when firmware updating. 

Changes since v13:
 - add const on data, ps8640_write_bytes(struct i2c_client *client, const u8 *data, u16 data_len)
 - fix PAGE2_SW_REST tyro.
 - move the buf[3] init to entrance of the function.

Changes since v12:
 - fix hw_chip_id build warning

Changes since v11:
 - Remove depends on I2C, add DRM depends
 - Reuse ps8640_write_bytes() in ps8640_write_byte()
 - Use timer check for polling like the routines in <linux/iopoll.h>
 - Fix no drm_connector_unregister/drm_connector_cleanup when ps8640_bridge_attach fail
 - Check the ps8640 hardware id in ps8640_validate_firmware
 - Remove fw_version check
 - Move ps8640_validate_firmware before ps8640_enter_bl
 - Add ddc_i2c unregister when probe fail and ps8640_remove
---
 drivers/gpu/drm/bridge/Kconfig         |   12 +
 drivers/gpu/drm/bridge/Makefile        |    1 +
 drivers/gpu/drm/bridge/parade-ps8640.c | 1067 ++++++++++++++++++++++++++++++++
 3 files changed, 1080 insertions(+)
 create mode 100644 drivers/gpu/drm/bridge/parade-ps8640.c

diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
index 8f7423f..02fea1a 100644
--- a/drivers/gpu/drm/bridge/Kconfig
+++ b/drivers/gpu/drm/bridge/Kconfig
@@ -50,6 +50,18 @@ config DRM_PARADE_PS8622
 	---help---
 	  Parade eDP-LVDS bridge chip driver.
 
+config DRM_PARADE_PS8640
+	tristate "Parade PS8640 MIPI DSI to eDP Converter"
+	depends on DRM
+	depends on OF
+	select DRM_KMS_HELPER
+	select DRM_MIPI_DSI
+	select DRM_PANEL
+	---help---
+	  Choose this option if you have PS8640 for display
+	  The PS8640 is a high-performance and low-power
+	  MIPI DSI to eDP converter
+
 source "drivers/gpu/drm/bridge/analogix/Kconfig"
 
 endmenu
diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
index 96b13b3..6c00b2f 100644
--- a/drivers/gpu/drm/bridge/Makefile
+++ b/drivers/gpu/drm/bridge/Makefile
@@ -6,3 +6,4 @@ obj-$(CONFIG_DRM_DW_HDMI_AHB_AUDIO) += dw-hdmi-ahb-audio.o
 obj-$(CONFIG_DRM_NXP_PTN3460) += nxp-ptn3460.o
 obj-$(CONFIG_DRM_PARADE_PS8622) += parade-ps8622.o
 obj-$(CONFIG_DRM_ANALOGIX_DP) += analogix/
+obj-$(CONFIG_DRM_PARADE_PS8640) += parade-ps8640.o
diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c
new file mode 100644
index 0000000..a73871e
--- /dev/null
+++ b/drivers/gpu/drm/bridge/parade-ps8640.c
@@ -0,0 +1,1067 @@
+/*
+ * Copyright (c) 2016 MediaTek Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * 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.
+ */
+
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/firmware.h>
+#include <linux/gpio.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_gpio.h>
+#include <linux/of_graph.h>
+#include <linux/regulator/consumer.h>
+#include <asm/unaligned.h>
+#include <drm/drm_panel.h>
+
+#include <drmP.h>
+#include <drm_atomic_helper.h>
+#include <drm_crtc_helper.h>
+#include <drm_crtc.h>
+#include <drm_edid.h>
+#include <drm_mipi_dsi.h>
+
+#define PAGE2_SPI_CFG3		0x82
+#define I2C_TO_SPI_RESET	0x20
+#define PAGE2_ROMADD_BYTE1	0x8e
+#define PAGE2_ROMADD_BYTE2	0x8f
+#define PAGE2_SWSPI_WDATA	0x90
+#define PAGE2_SWSPI_RDATA	0x91
+#define PAGE2_SWSPI_LEN		0x92
+#define PAGE2_SWSPI_CTL		0x93
+#define TRIGGER_NO_READBACK	0x05
+#define TRIGGER_READBACK	0x01
+#define PAGE2_SPI_STATUS	0x9e
+#define SPI_READY		0x0c
+#define PAGE2_GPIO_L		0xa6
+#define PAGE2_GPIO_H		0xa7
+#define PS_GPIO9		BIT(1)
+#define PAGE2_IROM_CTRL		0xb0
+#define IROM_ENABLE		0xc0
+#define IROM_DISABLE		0x80
+#define PAGE2_SW_RESET		0xbc
+#define SPI_SW_RESET		BIT(7)
+#define MPU_SW_RESET		BIT(6)
+#define PAGE2_ENCTLSPI_WR	0xda
+#define PAGE2_I2C_BYPASS	0xea
+#define I2C_BYPASS_EN		0xd0
+#define PAGE3_SET_ADD		0xfe
+#define PAGE3_SET_VAL		0xff
+#define VDO_CTL_ADD		0x13
+#define VDO_DIS			0x18
+#define VDO_EN			0x1c
+#define PAGE4_REV_L		0xf0
+#define PAGE4_REV_H		0xf1
+#define PAGE4_CHIP_L		0xf2
+#define PAGE4_CHIP_H		0xf3
+
+/* Firmware */
+#define SPI_MAX_RETRY_CNT	8
+#define PS_FW_NAME		"ps864x_fw.bin"
+
+#define FW_CHIP_ID_OFFSET	0
+#define FW_VERSION_OFFSET	2
+#define EDID_I2C_ADDR		0x50
+
+#define WRITE_STATUS_REG_CMD	0x01
+#define READ_STATUS_REG_CMD	0x05
+#define BUSY			BIT(0)
+#define CLEAR_ALL_PROTECT	0x00
+#define BLK_PROTECT_BITS	0x0c
+#define STATUS_REG_PROTECT	BIT(7)
+#define WRITE_ENABLE_CMD	0x06
+#define CHIP_ERASE_CMD		0xc7
+#define MAX_DEVS		0x8
+struct ps8640_info {
+	u8 family_id;
+	u8 variant_id;
+	u16 version;
+};
+
+struct ps8640 {
+	struct drm_connector connector;
+	struct drm_bridge bridge;
+	struct edid *edid;
+	struct mipi_dsi_device dsi;
+	struct i2c_client *page[MAX_DEVS];
+	struct i2c_client *ddc_i2c;
+	struct regulator_bulk_data supplies[2];
+	struct drm_panel *panel;
+	struct gpio_desc *gpio_rst_n;
+	struct gpio_desc *gpio_slp_n;
+	struct gpio_desc *gpio_mode_sel_n;
+	bool enabled;
+
+	/* firmware file info */
+	struct ps8640_info info;
+	bool in_fw_update;
+	/* for firmware update protect */
+	struct mutex fw_mutex;
+};
+
+static const u8 enc_ctrl_code[6] = { 0xaa, 0x55, 0x50, 0x41, 0x52, 0x44 };
+static const u8 hw_chip_id[4] = { 0x00, 0x0a, 0x00, 0x30 };
+
+static inline struct ps8640 *bridge_to_ps8640(struct drm_bridge *e)
+{
+	return container_of(e, struct ps8640, bridge);
+}
+
+static inline struct ps8640 *connector_to_ps8640(struct drm_connector *e)
+{
+	return container_of(e, struct ps8640, connector);
+}
+
+static int ps8640_read(struct i2c_client *client, u8 reg, u8 *data,
+		       u16 data_len)
+{
+	int ret;
+	struct i2c_msg msgs[] = {
+		{
+		 .addr = client->addr,
+		 .flags = 0,
+		 .len = 1,
+		 .buf = &reg,
+		},
+		{
+		 .addr = client->addr,
+		 .flags = I2C_M_RD,
+		 .len = data_len,
+		 .buf = data,
+		}
+	};
+
+	ret = i2c_transfer(client->adapter, msgs, 2);
+
+	if (ret == 2)
+		return 0;
+	if (ret < 0)
+		return ret;
+	else
+		return -EIO;
+}
+
+static int ps8640_write_bytes(struct i2c_client *client, const u8 *data,
+			      u16 data_len)
+{
+	int ret;
+	struct i2c_msg msg;
+
+	msg.addr = client->addr;
+	msg.flags = 0;
+	msg.len = data_len;
+	msg.buf = (u8 *)data;
+
+	ret = i2c_transfer(client->adapter, &msg, 1);
+	if (ret == 1)
+		return 0;
+	if (ret < 0)
+		return ret;
+	else
+		return -EIO;
+}
+
+static int ps8640_write_byte(struct i2c_client *client, u8 reg,  u8 data)
+{
+	u8 buf[] = { reg, data };
+
+	return ps8640_write_bytes(client, buf, sizeof(buf));
+}
+
+static void ps8640_get_mcu_fw_version(struct ps8640 *ps_bridge)
+{
+	struct i2c_client *client = ps_bridge->page[5];
+	u8 fw_ver[2];
+
+	ps8640_read(client, 0x4, fw_ver, sizeof(fw_ver));
+	ps_bridge->info.version = (fw_ver[0] << 8) | fw_ver[1];
+
+	DRM_INFO_ONCE("ps8640 rom fw version %d.%d\n", fw_ver[0], fw_ver[1]);
+}
+
+static int ps8640_bridge_unmute(struct ps8640 *ps_bridge)
+{
+	struct i2c_client *client = ps_bridge->page[3];
+	u8 vdo_ctrl_buf[3] = { PAGE3_SET_ADD, VDO_CTL_ADD, VDO_EN };
+
+	return ps8640_write_bytes(client, vdo_ctrl_buf, sizeof(vdo_ctrl_buf));
+}
+
+static int ps8640_bridge_mute(struct ps8640 *ps_bridge)
+{
+	struct i2c_client *client = ps_bridge->page[3];
+	u8 vdo_ctrl_buf[3] = { PAGE3_SET_ADD, VDO_CTL_ADD, VDO_DIS };
+
+	return ps8640_write_bytes(client, vdo_ctrl_buf, sizeof(vdo_ctrl_buf));
+}
+
+static void ps8640_pre_enable(struct drm_bridge *bridge)
+{
+	struct ps8640 *ps_bridge = bridge_to_ps8640(bridge);
+	struct i2c_client *client = ps_bridge->page[2];
+	int err;
+	u8 set_vdo_done;
+	ktime_t timeout;
+
+	if (ps_bridge->in_fw_update)
+		return;
+
+	if (ps_bridge->enabled)
+		return;
+
+	err = drm_panel_prepare(ps_bridge->panel);
+	if (err < 0) {
+		DRM_ERROR("failed to prepare panel: %d\n", err);
+		return;
+	}
+
+	err = regulator_bulk_enable(ARRAY_SIZE(ps_bridge->supplies),
+				    ps_bridge->supplies);
+	if (err < 0) {
+		DRM_ERROR("cannot enable regulators %d\n", err);
+		goto err_panel_unprepare;
+	}
+
+	gpiod_set_value(ps_bridge->gpio_slp_n, 1);
+	gpiod_set_value(ps_bridge->gpio_rst_n, 0);
+	usleep_range(2000, 2500);
+	gpiod_set_value(ps_bridge->gpio_rst_n, 1);
+
+	/*
+	 * Wait for the ps8640 embed mcu ready
+	 * First wait 200ms and then check the mcu ready flag every 20ms
+	 */
+	msleep(200);
+
+	timeout = ktime_add_ms(ktime_get(), 200);
+	for (;;) {
+		err = ps8640_read(client, PAGE2_GPIO_H, &set_vdo_done, 1);
+		if (err < 0) {
+			DRM_ERROR("failed read PAGE2_GPIO_H: %d\n", err);
+			goto err_regulators_disable;
+		}
+		if ((set_vdo_done & PS_GPIO9) == PS_GPIO9)
+			break;
+		if (ktime_compare(ktime_get(), timeout) > 0)
+			break;
+		msleep(20);
+	}
+
+	if (ps_bridge->info.version == 0)
+		ps8640_get_mcu_fw_version(ps_bridge);
+
+	err = ps8640_bridge_unmute(ps_bridge);
+	if (err)
+		DRM_ERROR("failed to enable unmutevideo: %d\n", err);
+	/* Switch access edp panel's edid through i2c */
+	ps8640_write_byte(client, PAGE2_I2C_BYPASS, I2C_BYPASS_EN);
+	ps_bridge->enabled = true;
+
+	return;
+
+err_regulators_disable:
+	regulator_bulk_disable(ARRAY_SIZE(ps_bridge->supplies),
+			       ps_bridge->supplies);
+err_panel_unprepare:
+	drm_panel_unprepare(ps_bridge->panel);
+}
+
+static void ps8640_enable(struct drm_bridge *bridge)
+{
+	struct ps8640 *ps_bridge = bridge_to_ps8640(bridge);
+	int err;
+
+	err = drm_panel_enable(ps_bridge->panel);
+	if (err < 0)
+		DRM_ERROR("failed to enable panel: %d\n", err);
+}
+
+static void ps8640_disable(struct drm_bridge *bridge)
+{
+	struct ps8640 *ps_bridge = bridge_to_ps8640(bridge);
+	int err;
+
+	err = drm_panel_disable(ps_bridge->panel);
+	if (err < 0)
+		DRM_ERROR("failed to disable panel: %d\n", err);
+}
+
+static void ps8640_post_disable(struct drm_bridge *bridge)
+{
+	struct ps8640 *ps_bridge = bridge_to_ps8640(bridge);
+	int err;
+
+	if (ps_bridge->in_fw_update)
+		return;
+
+	if (!ps_bridge->enabled)
+		return;
+
+	ps_bridge->enabled = false;
+
+	err = ps8640_bridge_mute(ps_bridge);
+	if (err < 0)
+		DRM_ERROR("failed to unmutevideo: %d\n", err);
+
+	gpiod_set_value(ps_bridge->gpio_rst_n, 0);
+	gpiod_set_value(ps_bridge->gpio_slp_n, 0);
+	err = regulator_bulk_disable(ARRAY_SIZE(ps_bridge->supplies),
+				     ps_bridge->supplies);
+	if (err < 0)
+		DRM_ERROR("cannot disable regulators %d\n", err);
+
+	err = drm_panel_unprepare(ps_bridge->panel);
+	if (err)
+		DRM_ERROR("failed to unprepare panel: %d\n", err);
+}
+
+static int ps8640_get_modes(struct drm_connector *connector)
+{
+	struct ps8640 *ps_bridge = connector_to_ps8640(connector);
+	struct device *dev = &ps_bridge->page[0]->dev;
+	struct edid *edid;
+	int num_modes = 0;
+	bool power_off;
+
+	if (ps_bridge->edid)
+		return drm_add_edid_modes(connector, ps_bridge->edid);
+
+	power_off = !ps_bridge->enabled;
+	ps8640_pre_enable(&ps_bridge->bridge);
+
+	edid = devm_kmalloc(dev, sizeof(edid), GFP_KERNEL);
+	if (!edid) {
+		DRM_ERROR("Failed to allocate EDID\n");
+		return 0;
+	}
+
+	edid = drm_get_edid(connector, ps_bridge->ddc_i2c->adapter);
+	if (!edid)
+		goto out;
+
+	ps_bridge->edid = edid;
+	drm_mode_connector_update_edid_property(connector, ps_bridge->edid);
+	num_modes = drm_add_edid_modes(connector, ps_bridge->edid);
+
+out:
+	if (power_off)
+		ps8640_post_disable(&ps_bridge->bridge);
+
+	return num_modes;
+}
+
+static struct drm_encoder *ps8640_best_encoder(struct drm_connector *connector)
+{
+	struct ps8640 *ps_bridge = connector_to_ps8640(connector);
+
+	return ps_bridge->bridge.encoder;
+}
+
+static const struct drm_connector_helper_funcs ps8640_connector_helper_funcs = {
+	.get_modes = ps8640_get_modes,
+	.best_encoder = ps8640_best_encoder,
+};
+
+static enum drm_connector_status ps8640_detect(struct drm_connector *connector,
+					       bool force)
+{
+	return connector_status_connected;
+}
+
+static const struct drm_connector_funcs ps8640_connector_funcs = {
+	.dpms = drm_atomic_helper_connector_dpms,
+	.fill_modes = drm_helper_probe_single_connector_modes,
+	.detect = ps8640_detect,
+	.reset = drm_atomic_helper_connector_reset,
+	.atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
+	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
+};
+
+int ps8640_bridge_attach(struct drm_bridge *bridge)
+{
+	struct ps8640 *ps_bridge = bridge_to_ps8640(bridge);
+	struct device *dev = &ps_bridge->page[0]->dev;
+	struct device_node *np = dev->of_node;
+	struct device_node *port, *in_ep;
+	struct device_node *dsi_node = NULL;
+	struct mipi_dsi_host *host = ps_bridge->dsi.host;
+	int ret;
+
+	ret = drm_connector_init(bridge->dev, &ps_bridge->connector,
+				 &ps8640_connector_funcs,
+				 DRM_MODE_CONNECTOR_eDP);
+
+	if (ret) {
+		DRM_ERROR("Failed to initialize connector with drm: %d\n", ret);
+		return ret;
+	}
+
+	drm_connector_helper_add(&ps_bridge->connector,
+				 &ps8640_connector_helper_funcs);
+
+	ps_bridge->connector.dpms = DRM_MODE_DPMS_ON;
+	drm_mode_connector_attach_encoder(&ps_bridge->connector,
+					  bridge->encoder);
+
+	if (ps_bridge->panel)
+		drm_panel_attach(ps_bridge->panel, &ps_bridge->connector);
+
+	/* port@0 is ps8640 dsi input port */
+	port = of_graph_get_port_by_id(np, 0);
+	if (port) {
+		in_ep = of_get_child_by_name(port, "endpoint");
+		of_node_put(port);
+		if (in_ep) {
+			dsi_node = of_graph_get_remote_port_parent(in_ep);
+			of_node_put(in_ep);
+		}
+	}
+	if (dsi_node) {
+		host = of_find_mipi_dsi_host_by_node(dsi_node);
+		of_node_put(dsi_node);
+		if (!host) {
+			ret = -ENODEV;
+			goto err;
+		}
+	}
+
+	ps_bridge->dsi.host = host;
+	ps_bridge->dsi.mode_flags = MIPI_DSI_MODE_VIDEO |
+				     MIPI_DSI_MODE_VIDEO_SYNC_PULSE;
+	ps_bridge->dsi.format = MIPI_DSI_FMT_RGB888;
+	ps_bridge->dsi.lanes = 4;
+	ret = mipi_dsi_attach(&ps_bridge->dsi);
+	if (ret)
+		goto err;
+
+	return 0;
+err:
+	if (ps_bridge->panel)
+		drm_panel_detach(ps_bridge->panel);
+	drm_connector_cleanup(&ps_bridge->connector);
+	return ret;
+}
+
+static const struct drm_bridge_funcs ps8640_bridge_funcs = {
+	.attach = ps8640_bridge_attach,
+	.disable = ps8640_disable,
+	.post_disable = ps8640_post_disable,
+	.pre_enable = ps8640_pre_enable,
+	.enable = ps8640_enable,
+};
+
+/* Firmware Version is returned as Major.Minor */
+static ssize_t ps8640_fw_version_show(struct device *dev,
+				      struct device_attribute *attr, char *buf)
+{
+	struct ps8640 *ps_bridge = dev_get_drvdata(dev);
+	struct ps8640_info *info = &ps_bridge->info;
+
+	return scnprintf(buf, PAGE_SIZE, "%u.%u\n", info->version >> 8,
+			 info->version & 0xff);
+}
+
+/* Hardware Version is returned as FamilyID.VariantID */
+static ssize_t ps8640_hw_version_show(struct device *dev,
+				      struct device_attribute *attr, char *buf)
+{
+	struct ps8640 *ps_bridge = dev_get_drvdata(dev);
+	struct ps8640_info *info = &ps_bridge->info;
+
+	return scnprintf(buf, PAGE_SIZE, "ps%u.%u\n", info->family_id,
+			 info->variant_id);
+}
+
+static int ps8640_spi_send_cmd(struct ps8640 *ps_bridge, u8 *cmd, u8 cmd_len)
+{
+	struct i2c_client *client = ps_bridge->page[2];
+	u8 i, buf[3] = { PAGE2_SWSPI_LEN, cmd_len - 1, TRIGGER_NO_READBACK };
+	int ret;
+
+	ret = ps8640_write_byte(client, PAGE2_IROM_CTRL, IROM_ENABLE);
+	if (ret)
+		goto err;
+
+	/* write command in write port */
+	for (i = 0; i < cmd_len; i++) {
+		ret = ps8640_write_byte(client, PAGE2_SWSPI_WDATA, cmd[i]);
+		if (ret)
+			goto err_irom_disable;
+	}
+
+	ret = ps8640_write_bytes(client, buf, sizeof(buf));
+	if (ret)
+		goto err_irom_disable;
+
+	ret = ps8640_write_byte(client, PAGE2_IROM_CTRL, IROM_DISABLE);
+	if (ret)
+		goto err;
+
+	return 0;
+err_irom_disable:
+	ps8640_write_byte(client, PAGE2_IROM_CTRL, IROM_DISABLE);
+err:
+	dev_err(&client->dev, "send command err: %d\n", ret);
+	return ret;
+}
+
+static int ps8640_wait_spi_ready(struct ps8640 *ps_bridge)
+{
+	struct i2c_client *client = ps_bridge->page[2];
+	u8 spi_rdy_st;
+	ktime_t timeout;
+
+	timeout = ktime_add_ms(ktime_get(), 200);
+	for (;;) {
+		ps8640_read(client, PAGE2_SPI_STATUS, &spi_rdy_st, 1);
+		if ((spi_rdy_st & SPI_READY) != SPI_READY)
+			break;
+
+		if (ktime_compare(ktime_get(), timeout) > 0) {
+			dev_err(&client->dev, "wait spi ready timeout\n");
+			return -EBUSY;
+		}
+
+		msleep(20);
+	}
+
+	return 0;
+}
+
+static int ps8640_wait_spi_nobusy(struct ps8640 *ps_bridge)
+{
+	struct i2c_client *client = ps_bridge->page[2];
+	u8 spi_status, buf[3] = { PAGE2_SWSPI_LEN, 0, TRIGGER_READBACK };
+	int ret;
+	ktime_t timeout;
+
+	timeout = ktime_add_ms(ktime_get(), 500);
+	for (;;) {
+		/* 0x05 RDSR; Read-Status-Register */
+		ret = ps8640_write_byte(client, PAGE2_SWSPI_WDATA,
+					READ_STATUS_REG_CMD);
+		if (ret)
+			goto err_send_cmd_exit;
+
+		ret = ps8640_write_bytes(client, buf, 3);
+		if (ret)
+			goto err_send_cmd_exit;
+
+		/* delay for cmd send */
+		usleep_range(300, 500);
+		/* wait for SPI ROM until not busy */
+		ret = ps8640_read(client, PAGE2_SWSPI_RDATA, &spi_status, 1);
+		if (ret)
+			goto err_send_cmd_exit;
+
+		if (!(spi_status & BUSY))
+			break;
+
+		if (ktime_compare(ktime_get(), timeout) > 0) {
+			dev_err(&client->dev, "wait spi no busy timeout: %d\n",
+				ret);
+			return -EBUSY;
+		}
+	}
+
+	return 0;
+
+err_send_cmd_exit:
+	dev_err(&client->dev, "send command err: %d\n", ret);
+	return ret;
+}
+
+static int ps8640_wait_rom_idle(struct ps8640 *ps_bridge)
+{
+	struct i2c_client *client = ps_bridge->page[0];
+	int ret;
+
+	ret = ps8640_write_byte(client, PAGE2_IROM_CTRL, IROM_ENABLE);
+	if (ret)
+		goto exit;
+
+	ret = ps8640_wait_spi_ready(ps_bridge);
+	if (ret)
+		goto err_spi;
+
+	ret = ps8640_wait_spi_nobusy(ps_bridge);
+	if (ret)
+		goto err_spi;
+
+	ret = ps8640_write_byte(client, PAGE2_IROM_CTRL, IROM_DISABLE);
+	if (ret)
+		goto exit;
+
+	return 0;
+
+err_spi:
+	ps8640_write_byte(client, PAGE2_IROM_CTRL, IROM_DISABLE);
+exit:
+	if (ret)
+		dev_err(&client->dev, "wait ps8640 rom idle fail: %d\n", ret);
+
+	return ret;
+}
+
+static int ps8640_spi_dl_mode(struct ps8640 *ps_bridge)
+{
+	struct i2c_client *client = ps_bridge->page[2];
+	int ret;
+
+	/* switch ps8640 mode to spi dl mode */
+	if (ps_bridge->gpio_mode_sel_n)
+		gpiod_set_value(ps_bridge->gpio_mode_sel_n, 0);
+
+	/* reset spi interface */
+	ret = ps8640_write_byte(client, PAGE2_SW_RESET,
+				SPI_SW_RESET | MPU_SW_RESET);
+	if (ret)
+		goto exit;
+
+	ret = ps8640_write_byte(client, PAGE2_SW_RESET, MPU_SW_RESET);
+	if (ret)
+		goto exit;
+
+exit:
+	if (ret)
+		dev_err(&client->dev, "fail reset spi interface: %d\n", ret);
+
+	return ret;
+}
+
+static int ps8640_rom_prepare(struct ps8640 *ps_bridge)
+{
+	struct i2c_client *client = ps_bridge->page[2];
+	struct device *dev = &client->dev;
+	u8 i, cmd[2];
+	int ret;
+
+	cmd[0] = WRITE_ENABLE_CMD;
+	ret = ps8640_spi_send_cmd(ps_bridge, cmd, 1);
+	if (ret) {
+		dev_err(dev, "failed enable-write-status-register: %d\n", ret);
+		return ret;
+	}
+
+	cmd[0] = WRITE_STATUS_REG_CMD;
+	cmd[1] = CLEAR_ALL_PROTECT;
+	ret = ps8640_spi_send_cmd(ps_bridge, cmd, 2);
+	if (ret) {
+		dev_err(dev, "fail disable all protection: %d\n", ret);
+		return ret;
+	}
+
+	/* wait for SPI module ready */
+	ret = ps8640_wait_rom_idle(ps_bridge);
+	if (ret) {
+		dev_err(dev, "fail wait rom idle: %d\n", ret);
+		return ret;
+	}
+
+	ps8640_write_byte(client, PAGE2_IROM_CTRL, IROM_ENABLE);
+	for (i = 0; i < 6; i++)
+		ps8640_write_byte(client, PAGE2_ENCTLSPI_WR, enc_ctrl_code[i]);
+	ps8640_write_byte(client, PAGE2_IROM_CTRL, IROM_DISABLE);
+
+	/* Enable-Write-Status-Register */
+	cmd[0] = WRITE_ENABLE_CMD;
+	ret = ps8640_spi_send_cmd(ps_bridge, cmd, 1);
+	if (ret) {
+		dev_err(dev, "fail enable-write-status-register: %d\n", ret);
+		return ret;
+	}
+
+	/* chip erase command */
+	cmd[0] = CHIP_ERASE_CMD;
+	ret = ps8640_spi_send_cmd(ps_bridge, cmd, 1);
+	if (ret) {
+		dev_err(dev, "fail disable all protection: %d\n", ret);
+		return ret;
+	}
+
+	ret = ps8640_wait_rom_idle(ps_bridge);
+	if (ret) {
+		dev_err(dev, "fail wait rom idle: %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int ps8640_check_chip_id(struct ps8640 *ps_bridge)
+{
+	struct i2c_client *client = ps_bridge->page[4];
+	u8 buf[4];
+
+	ps8640_read(client, PAGE4_REV_L, buf, 4);
+	return memcmp(buf, hw_chip_id, sizeof(buf));
+}
+
+static int ps8640_validate_firmware(struct ps8640 *ps_bridge,
+				    const struct firmware *fw)
+{
+	struct i2c_client *client = ps_bridge->page[0];
+	u16 fw_chip_id;
+
+	/*
+	 * Get the chip_id from the firmware. Make sure that it is the
+	 * right controller to do the firmware and config update.
+	 */
+	fw_chip_id = get_unaligned_le16(fw->data + FW_CHIP_ID_OFFSET);
+
+	if (fw_chip_id != 0x8640 && ps8640_check_chip_id(ps_bridge) == 0) {
+		dev_err(&client->dev,
+			"chip id mismatch: fw 0x%x vs. chip 0x8640\n",
+			fw_chip_id);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int ps8640_write_rom(struct ps8640 *ps_bridge, const struct firmware *fw)
+{
+	struct i2c_client *client = ps_bridge->page[0];
+	struct device *dev = &client->dev;
+	struct i2c_client *client2 = ps_bridge->page[2];
+	struct i2c_client *client7 = ps_bridge->page[7];
+	size_t pos;
+	u8 buf[257], rom_page_id_buf[3];
+	int ret;
+	u16 cpy_len;
+
+	ps8640_write_byte(client2, PAGE2_SPI_CFG3, I2C_TO_SPI_RESET);
+	msleep(100);
+	ps8640_write_byte(client2, PAGE2_SPI_CFG3, 0x00);
+
+	for (pos = 0; pos < fw->size; pos += cpy_len) {
+		rom_page_id_buf[0] = PAGE2_ROMADD_BYTE1;
+		rom_page_id_buf[1] = pos >> 8;
+		rom_page_id_buf[2] = pos >> 16;
+		ret = ps8640_write_bytes(client2, rom_page_id_buf, 3);
+		if (ret)
+			goto error;
+		cpy_len = fw->size >= 256 + pos ? 256 : fw->size - pos;
+		buf[0] = 0;
+		memcpy(buf + 1, fw->data + pos, cpy_len);
+		ret = ps8640_write_bytes(client7, buf, cpy_len + 1);
+		if (ret)
+			goto error;
+
+		dev_dbg(dev, "fw update completed %zu / %zu bytes\n", pos,
+			fw->size);
+	}
+	return 0;
+
+error:
+	dev_err(dev, "failed write external flash, %d\n", ret);
+	return ret;
+}
+
+static int ps8640_spi_normal_mode(struct ps8640 *ps_bridge)
+{
+	u8 cmd[2];
+	struct i2c_client *client = ps_bridge->page[2];
+
+	/* Enable-Write-Status-Register */
+	cmd[0] = WRITE_ENABLE_CMD;
+	ps8640_spi_send_cmd(ps_bridge, cmd, 1);
+
+	/* protect BPL/BP0/BP1 */
+	cmd[0] = WRITE_STATUS_REG_CMD;
+	cmd[1] = BLK_PROTECT_BITS | STATUS_REG_PROTECT;
+	ps8640_spi_send_cmd(ps_bridge, cmd, 2);
+
+	/* wait for SPI rom ready */
+	ps8640_wait_rom_idle(ps_bridge);
+
+	/* disable PS8640 mapping function */
+	ps8640_write_byte(client, PAGE2_ENCTLSPI_WR, 0x00);
+
+	if (ps_bridge->gpio_mode_sel_n)
+		gpiod_set_value(ps_bridge->gpio_mode_sel_n, 1);
+	return 0;
+}
+
+static int ps8640_enter_bl(struct ps8640 *ps_bridge)
+{
+	ps_bridge->in_fw_update = true;
+	return ps8640_spi_dl_mode(ps_bridge);
+}
+
+static void ps8640_exit_bl(struct ps8640 *ps_bridge, const struct firmware *fw)
+{
+	ps8640_spi_normal_mode(ps_bridge);
+	ps_bridge->in_fw_update = false;
+}
+
+static int ps8640_load_fw(struct ps8640 *ps_bridge, const struct firmware *fw)
+{
+	struct i2c_client *client = ps_bridge->page[0];
+	struct device *dev = &client->dev;
+	int ret;
+	bool ps8640_status_backup = ps_bridge->enabled;
+
+	ret = ps8640_validate_firmware(ps_bridge, fw);
+	if (ret)
+		return ret;
+
+	mutex_lock(&ps_bridge->fw_mutex);
+	if (!ps_bridge->in_fw_update) {
+		if (!ps8640_status_backup)
+			ps8640_pre_enable(&ps_bridge->bridge);
+
+		ret = ps8640_enter_bl(ps_bridge);
+		if (ret)
+			goto exit;
+	}
+
+	ret = ps8640_rom_prepare(ps_bridge);
+	if (ret)
+		goto exit;
+
+	ret = ps8640_write_rom(ps_bridge, fw);
+
+exit:
+	if (ret)
+		dev_err(dev, "Failed to load firmware, %d\n", ret);
+
+	ps8640_exit_bl(ps_bridge, fw);
+	if (!ps8640_status_backup)
+		ps8640_post_disable(&ps_bridge->bridge);
+	mutex_unlock(&ps_bridge->fw_mutex);
+	return ret;
+}
+
+static ssize_t ps8640_update_fw_store(struct device *dev,
+				      struct device_attribute *attr,
+				      const char *buf, size_t count)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct ps8640 *ps_bridge = i2c_get_clientdata(client);
+	const struct firmware *fw;
+	int error;
+
+	error = request_firmware(&fw, PS_FW_NAME, dev);
+	if (error) {
+		dev_err(dev, "Unable to open firmware %s: %d\n",
+			PS_FW_NAME, error);
+		return error;
+	}
+
+	error = ps8640_load_fw(ps_bridge, fw);
+	if (error)
+		dev_err(dev, "The firmware update failed(%d)\n", error);
+	else
+		dev_info(dev, "The firmware update succeeded\n");
+
+	release_firmware(fw);
+	return error ? error : count;
+}
+
+static DEVICE_ATTR(fw_version, S_IRUGO, ps8640_fw_version_show, NULL);
+static DEVICE_ATTR(hw_version, S_IRUGO, ps8640_hw_version_show, NULL);
+static DEVICE_ATTR(update_fw, S_IWUSR, NULL, ps8640_update_fw_store);
+
+static struct attribute *ps8640_attrs[] = {
+	&dev_attr_fw_version.attr,
+	&dev_attr_hw_version.attr,
+	&dev_attr_update_fw.attr,
+	NULL
+};
+
+static const struct attribute_group ps8640_attr_group = {
+	.attrs = ps8640_attrs,
+};
+
+static void ps8640_remove_sysfs_group(void *data)
+{
+	struct ps8640 *ps_bridge = data;
+
+	sysfs_remove_group(&ps_bridge->page[0]->dev.kobj, &ps8640_attr_group);
+}
+
+static int ps8640_probe(struct i2c_client *client,
+			const struct i2c_device_id *id)
+{
+	struct device *dev = &client->dev;
+	struct ps8640 *ps_bridge;
+	struct device_node *np = dev->of_node;
+	struct device_node *port, *out_ep;
+	struct device_node *panel_node = NULL;
+	int ret;
+	u32 i;
+
+	ps_bridge = devm_kzalloc(dev, sizeof(*ps_bridge), GFP_KERNEL);
+	if (!ps_bridge)
+		return -ENOMEM;
+
+	/* port@1 is ps8640 output port */
+	port = of_graph_get_port_by_id(np, 1);
+	if (port) {
+		out_ep = of_get_child_by_name(port, "endpoint");
+		of_node_put(port);
+		if (out_ep) {
+			panel_node = of_graph_get_remote_port_parent(out_ep);
+			of_node_put(out_ep);
+		}
+	}
+	if (panel_node) {
+		ps_bridge->panel = of_drm_find_panel(panel_node);
+		of_node_put(panel_node);
+		if (!ps_bridge->panel)
+			return -EPROBE_DEFER;
+	}
+
+	mutex_init(&ps_bridge->fw_mutex);
+	ps_bridge->supplies[0].supply = "vdd33";
+	ps_bridge->supplies[1].supply = "vdd12";
+	ret = devm_regulator_bulk_get(dev, ARRAY_SIZE(ps_bridge->supplies),
+				      ps_bridge->supplies);
+	if (ret) {
+		dev_info(dev, "failed to get regulators: %d\n", ret);
+		return ret;
+	}
+
+	ps_bridge->gpio_mode_sel_n = devm_gpiod_get_optional(&client->dev,
+							     "mode-sel",
+							     GPIOD_OUT_HIGH);
+	if (IS_ERR(ps_bridge->gpio_mode_sel_n)) {
+		ret = PTR_ERR(ps_bridge->gpio_mode_sel_n);
+		dev_err(dev, "cannot get mode-sel %d\n", ret);
+		return ret;
+	}
+
+	ps_bridge->gpio_slp_n = devm_gpiod_get(&client->dev, "sleep",
+					       GPIOD_OUT_LOW);
+	if (IS_ERR(ps_bridge->gpio_slp_n)) {
+		ret = PTR_ERR(ps_bridge->gpio_slp_n);
+		dev_err(dev, "cannot get sleep: %d\n", ret);
+		return ret;
+	}
+
+	/*
+	 * Request the reset pin low to avoid the bridge being
+	 * initialized prematurely
+	 */
+	ps_bridge->gpio_rst_n = devm_gpiod_get(&client->dev, "reset",
+					       GPIOD_OUT_LOW);
+	if (IS_ERR(ps_bridge->gpio_rst_n)) {
+		ret = PTR_ERR(ps_bridge->gpio_rst_n);
+		dev_err(dev, "cannot get reset: %d\n", ret);
+		return ret;
+	}
+
+	ps_bridge->bridge.funcs = &ps8640_bridge_funcs;
+	ps_bridge->bridge.of_node = dev->of_node;
+
+	ps_bridge->page[0] = client;
+	ps_bridge->ddc_i2c = i2c_new_dummy(client->adapter, EDID_I2C_ADDR);
+	if (!ps_bridge->ddc_i2c) {
+		dev_err(dev, "failed ddc_i2c dummy device, address%02x\n",
+			EDID_I2C_ADDR);
+		return -EBUSY;
+	}
+	/*
+	 * ps8640 uses multiple addresses, use dummy devices for them
+	 * page[0]: for DP control
+	 * page[1]: for VIDEO Bridge
+	 * page[2]: for control top
+	 * page[3]: for DSI Link Control1
+	 * page[4]: for MIPI Phy
+	 * page[5]: for VPLL
+	 * page[6]: for DSI Link Control2
+	 * page[7]: for spi rom mapping
+	 */
+	for (i = 1; i < MAX_DEVS; i++) {
+		ps_bridge->page[i] = i2c_new_dummy(client->adapter,
+						   client->addr + i);
+		if (!ps_bridge->page[i]) {
+			dev_err(dev, "failed i2c dummy device, address%02x\n",
+				client->addr + i);
+			ret = -EBUSY;
+			goto exit_dummy;
+		}
+	}
+	i2c_set_clientdata(client, ps_bridge);
+
+	ret = sysfs_create_group(&client->dev.kobj, &ps8640_attr_group);
+	if (ret) {
+		dev_err(dev, "failed to create sysfs entries: %d\n", ret);
+		goto exit_dummy;
+	}
+
+	ret = devm_add_action(dev, ps8640_remove_sysfs_group, ps_bridge);
+	if (ret) {
+		dev_err(dev, "failed to add sysfs cleanup action: %d\n", ret);
+		goto exit_remove_sysfs;
+	}
+
+	ret = drm_bridge_add(&ps_bridge->bridge);
+	if (ret) {
+		dev_err(dev, "Failed to add bridge: %d\n", ret);
+		goto exit_remove_sysfs;
+	}
+	return 0;
+
+exit_remove_sysfs:
+	sysfs_remove_group(&ps_bridge->page[0]->dev.kobj, &ps8640_attr_group);
+exit_dummy:
+	while (--i)
+		i2c_unregister_device(ps_bridge->page[i]);
+	i2c_unregister_device(ps_bridge->ddc_i2c);
+	return ret;
+}
+
+static int ps8640_remove(struct i2c_client *client)
+{
+	struct ps8640 *ps_bridge = i2c_get_clientdata(client);
+	int i = MAX_DEVS;
+
+	drm_bridge_remove(&ps_bridge->bridge);
+	sysfs_remove_group(&ps_bridge->page[0]->dev.kobj, &ps8640_attr_group);
+	while (--i)
+		i2c_unregister_device(ps_bridge->page[i]);
+
+	i2c_unregister_device(ps_bridge->ddc_i2c);
+	return 0;
+}
+
+static const struct i2c_device_id ps8640_i2c_table[] = {
+	{ "parade,ps8640", 0 },
+	{},
+};
+MODULE_DEVICE_TABLE(i2c, ps8640_i2c_table);
+
+static const struct of_device_id ps8640_match[] = {
+	{ .compatible = "parade,ps8640" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, ps8640_match);
+
+static struct i2c_driver ps8640_driver = {
+	.id_table = ps8640_i2c_table,
+	.probe = ps8640_probe,
+	.remove = ps8640_remove,
+	.driver = {
+		.name = "parade,ps8640",
+		.of_match_table = ps8640_match,
+	},
+};
+module_i2c_driver(ps8640_driver);
+
+MODULE_AUTHOR("Jitao Shi <jitao.shi@mediatek.com>");
+MODULE_AUTHOR("CK Hu <ck.hu@mediatek.com>");
+MODULE_DESCRIPTION("PARADE ps8640 DSI-eDP converter driver");
+MODULE_LICENSE("GPL v2");
-- 
1.7.9.5

Re: [PATCH 2/2 v16] drm/bridge: Add I2C based driver for ps8640 bridge

[Daniel Kurtz]

Hi Jitao,

On Thu, Jun 2, 2016 at 5:57 PM, Jitao Shi <jitao.shi@mediatek.com> wrote:
>
> This patch adds drm_bridge driver for parade DSI to eDP bridge chip.
>
> Signed-off-by: Jitao Shi <jitao.shi@mediatek.com>
> Reviewed-by: Daniel Kurtz <djkurtz@chromium.org>
> ---
> Changes since v15:
>  - Drop drm_connector_(un)register calls from parade ps8640.
>    The main DRM driver mtk_drm_drv now calls
>    drm_connector_register_all() after drm_dev_register() in the
>    mtk_drm_bind() function. That function should iterate over all
>    connectors and call drm_connector_register() for each of them.
>    So, remove drm_connector_(un)register calls from parade ps8640.

[snip...]

> +static void ps8640_pre_enable(struct drm_bridge *bridge)
> +{
> +       struct ps8640 *ps_bridge = bridge_to_ps8640(bridge);
> +       struct i2c_client *client = ps_bridge->page[2];
> +       int err;
> +       u8 set_vdo_done;
> +       ktime_t timeout;
> +
> +       if (ps_bridge->in_fw_update)
> +               return;
> +
> +       if (ps_bridge->enabled)
> +               return;
> +
> +       err = drm_panel_prepare(ps_bridge->panel);
> +       if (err < 0) {
> +               DRM_ERROR("failed to prepare panel: %d\n", err);
> +               return;
> +       }
> +

(1) For patch v10, Philipp Zabel commented that gpio_slp_n &
gpio_rst_n are both active low, and that the device tree should
contain a reset-gpios property with the GPIO_ACTIVE_LOW flag set.
(2) However, you did change the the reset logic from v10 -> v11, but
it isn't clear why (nor mentioned in the patch notes).

v10 (https://patchwork.kernel.org/patch/8357851/) had:

+ gpiod_set_value(ps_bridge->gpio_slp_n, 1);
+ gpiod_set_value(ps_bridge->gpio_rst_n, 0);
+
+ err = regulator_bulk_enable(ARRAY_SIZE(ps_bridge->supplies),
+    ps_bridge->supplies);
+ if (err < 0) {
+ DRM_ERROR("cannot enable regulators %d\n", err);
+ goto err_panel_unprepare;
+ }
+
+ usleep_range(500, 700);
+ gpiod_set_value(ps_bridge->gpio_rst_n, 1);

In other words:
  (a) de-assert power down
  (b) assert reset
  (c) enable 1.2 & 3.3 regulators
  (d) <wait for  regulator delay> (aka regulator-ramp-delay in device-tree)
  (e) wait an additional 2 ms (as requested by Parade for ps8640 to stabilize?)
  (f) de-assert reset
  (g) wait 200 ms (for ps8640 FW to load?)

This mostly made sense to me, except for step (a)... I'm not sure why
you de-assert power down before enabling the regulators.  It seems
like you'd want to do that later, maybe after reset (can you ask
Paradetech?).

Now (as of v11) it has changed to:

> +       err = regulator_bulk_enable(ARRAY_SIZE(ps_bridge->supplies),
> +                                   ps_bridge->supplies);
> +       if (err < 0) {
> +               DRM_ERROR("cannot enable regulators %d\n", err);
> +               goto err_panel_unprepare;
> +       }
> +
> +       gpiod_set_value(ps_bridge->gpio_slp_n, 1);
> +       gpiod_set_value(ps_bridge->gpio_rst_n, 0);
> +       usleep_range(2000, 2500);
> +       gpiod_set_value(ps_bridge->gpio_rst_n, 1);

Two additional comments:

(3) if you correctly configure these gpios as GPIO_ACTIVE_LOW, you can
drop the "_n" suffix, which will make the driver code easier to
understand.
(4) "gpio_slp_n" is called "PD#" by the PS8640 datasheet, so a better
name might be: "gpio_power_down".

Thanks,
-Dan

Re: [PATCH 2/2 v16] drm/bridge: Add I2C based driver for ps8640 bridge

[Emil Velikov]

Hi Jitao Shi,

A few comments/suggestions which I hope you'll find useful. Note that
I'm not an expert in the area so take them with a pinch of salt.

On 2 June 2016 at 10:57, Jitao Shi <jitao.shi@mediatek.com> wrote:

> +#define WRITE_STATUS_REG_CMD   0x01
> +#define READ_STATUS_REG_CMD    0x05
> +#define BUSY                   BIT(0)
> +#define CLEAR_ALL_PROTECT      0x00
> +#define BLK_PROTECT_BITS       0x0c
> +#define STATUS_REG_PROTECT     BIT(7)
> +#define WRITE_ENABLE_CMD       0x06
> +#define CHIP_ERASE_CMD         0xc7
> +#define MAX_DEVS               0x8
Some of the above are unused - SPI_MAX_RETRY_CNT and PAGE2_SWSPI_CTL
come to might. Please double-check and nuke any unused ones for now ?

Add blank line between the macro definitions and the struct.

> +struct ps8640_info {
> +       u8 family_id;
> +       u8 variant_id;
> +       u16 version;
> +};
> +
> +struct ps8640 {
> +       struct drm_connector connector;
> +       struct drm_bridge bridge;
> +       struct edid *edid;
> +       struct mipi_dsi_device dsi;
> +       struct i2c_client *page[MAX_DEVS];
Throw in an enum that provides symbolic names for the different i2c
clients and rename "page" to clients or anything else that makes it
clearer ? Seems like '1' and '6' are never used.

Using better names than client2/7 in the actual code will be great :-)

> +       struct i2c_client *ddc_i2c;
> +       struct regulator_bulk_data supplies[2];
> +       struct drm_panel *panel;
> +       struct gpio_desc *gpio_rst_n;
> +       struct gpio_desc *gpio_slp_n;
> +       struct gpio_desc *gpio_mode_sel_n;
What does the _n suffix mean in the above three ? Bikeshed:
reset_gpio, sleep_gpio and mode_sel(ect)_gpio could also be used ;-)

> +       bool enabled;
> +
> +       /* firmware file info */
> +       struct ps8640_info info;
> +       bool in_fw_update;
> +       /* for firmware update protect */
> +       struct mutex fw_mutex;
> +};
> +
> +static const u8 enc_ctrl_code[6] = { 0xaa, 0x55, 0x50, 0x41, 0x52, 0x44 };
These feel a bit magical. Any chance you can give them symbolic names ?

> +static const u8 hw_chip_id[4] = { 0x00, 0x0a, 0x00, 0x30 };
> +
> +static inline struct ps8640 *bridge_to_ps8640(struct drm_bridge *e)
> +{
> +       return container_of(e, struct ps8640, bridge);
> +}
> +
> +static inline struct ps8640 *connector_to_ps8640(struct drm_connector *e)
> +{
> +       return container_of(e, struct ps8640, connector);
> +}
> +
> +static int ps8640_read(struct i2c_client *client, u8 reg, u8 *data,
> +                      u16 data_len)
> +{
> +       int ret;
> +       struct i2c_msg msgs[] = {
> +               {
> +                .addr = client->addr,
> +                .flags = 0,
> +                .len = 1,
> +                .buf = &reg,
> +               },
> +               {
> +                .addr = client->addr,
> +                .flags = I2C_M_RD,
> +                .len = data_len,
> +                .buf = data,
> +               }
> +       };
> +
> +       ret = i2c_transfer(client->adapter, msgs, 2);
> +
> +       if (ret == 2)
> +               return 0;
> +       if (ret < 0)
> +               return ret;
> +       else
> +               return -EIO;
> +}
> +
> +static int ps8640_write_bytes(struct i2c_client *client, const u8 *data,
> +                             u16 data_len)
> +{
> +       int ret;
> +       struct i2c_msg msg;
> +
> +       msg.addr = client->addr;
> +       msg.flags = 0;
> +       msg.len = data_len;
> +       msg.buf = (u8 *)data;
> +
> +       ret = i2c_transfer(client->adapter, &msg, 1);
> +       if (ret == 1)
> +               return 0;
> +       if (ret < 0)
> +               return ret;
> +       else
> +               return -EIO;
> +}
> +
> +static int ps8640_write_byte(struct i2c_client *client, u8 reg,  u8 data)
> +{
> +       u8 buf[] = { reg, data };
> +
> +       return ps8640_write_bytes(client, buf, sizeof(buf));
> +}
> +
> +static void ps8640_get_mcu_fw_version(struct ps8640 *ps_bridge)
> +{
> +       struct i2c_client *client = ps_bridge->page[5];
> +       u8 fw_ver[2];
> +
> +       ps8640_read(client, 0x4, fw_ver, sizeof(fw_ver));
> +       ps_bridge->info.version = (fw_ver[0] << 8) | fw_ver[1];
> +
> +       DRM_INFO_ONCE("ps8640 rom fw version %d.%d\n", fw_ver[0], fw_ver[1]);
> +}
> +
> +static int ps8640_bridge_unmute(struct ps8640 *ps_bridge)
> +{
> +       struct i2c_client *client = ps_bridge->page[3];
> +       u8 vdo_ctrl_buf[3] = { PAGE3_SET_ADD, VDO_CTL_ADD, VDO_EN };
> +
> +       return ps8640_write_bytes(client, vdo_ctrl_buf, sizeof(vdo_ctrl_buf));
> +}
> +
> +static int ps8640_bridge_mute(struct ps8640 *ps_bridge)
> +{
> +       struct i2c_client *client = ps_bridge->page[3];
> +       u8 vdo_ctrl_buf[3] = { PAGE3_SET_ADD, VDO_CTL_ADD, VDO_DIS };
> +
> +       return ps8640_write_bytes(client, vdo_ctrl_buf, sizeof(vdo_ctrl_buf));
> +}
> +
> +static void ps8640_pre_enable(struct drm_bridge *bridge)
> +{
> +       struct ps8640 *ps_bridge = bridge_to_ps8640(bridge);
> +       struct i2c_client *client = ps_bridge->page[2];
> +       int err;
> +       u8 set_vdo_done;
> +       ktime_t timeout;
> +
> +       if (ps_bridge->in_fw_update)
> +               return;
> +
> +       if (ps_bridge->enabled)
> +               return;
> +
> +       err = drm_panel_prepare(ps_bridge->panel);
> +       if (err < 0) {
> +               DRM_ERROR("failed to prepare panel: %d\n", err);
> +               return;
> +       }
> +
> +       err = regulator_bulk_enable(ARRAY_SIZE(ps_bridge->supplies),
> +                                   ps_bridge->supplies);
> +       if (err < 0) {
> +               DRM_ERROR("cannot enable regulators %d\n", err);
> +               goto err_panel_unprepare;
> +       }
> +
> +       gpiod_set_value(ps_bridge->gpio_slp_n, 1);
> +       gpiod_set_value(ps_bridge->gpio_rst_n, 0);
> +       usleep_range(2000, 2500);
> +       gpiod_set_value(ps_bridge->gpio_rst_n, 1);
> +
> +       /*
> +        * Wait for the ps8640 embed mcu ready
> +        * First wait 200ms and then check the mcu ready flag every 20ms
> +        */
> +       msleep(200);
> +

> +       timeout = ktime_add_ms(ktime_get(), 200);
> +       for (;;) {
> +               err = ps8640_read(client, PAGE2_GPIO_H, &set_vdo_done, 1);
> +               if (err < 0) {
> +                       DRM_ERROR("failed read PAGE2_GPIO_H: %d\n", err);
> +                       goto err_regulators_disable;
> +               }
> +               if ((set_vdo_done & PS_GPIO9) == PS_GPIO9)
> +                       break;
> +               if (ktime_compare(ktime_get(), timeout) > 0)
> +                       break;
> +               msleep(20);
> +       }
> +
This is the first such construct in DRM. Is there anything wrong using
something like the following ? Same question applies for the rest of
the patch.


count = XX;

for (i = 0; i < count; i++) {
    err = ps8640_read(client, PAGE2_GPIO_H, &set_vdo_done, 1);
    if (err < 0) {
        DRM_ERROR("failed read PAGE2_GPIO_H: %d\n", err);
        goto err_regulators_disable;
    }
    if ((set_vdo_done & PS_GPIO9) == PS_GPIO9)
        break;

    msleep(20);
}

if (i == count) {
    print_some_warning()
    error_out()
}



> +static int ps8640_get_modes(struct drm_connector *connector)
> +{

> +
> +       edid = devm_kmalloc(dev, sizeof(edid), GFP_KERNEL);
> +       if (!edid) {
> +               DRM_ERROR("Failed to allocate EDID\n");
> +               return 0;
Remove this. drm_get_edid() already returns a kmalloc'd hunk of memory.

> +       }
> +
> +       edid = drm_get_edid(connector, ps_bridge->ddc_i2c->adapter);
> +       if (!edid)
> +               goto out;
> +


> +int ps8640_bridge_attach(struct drm_bridge *bridge)
> +{
> +       struct ps8640 *ps_bridge = bridge_to_ps8640(bridge);
> +       struct device *dev = &ps_bridge->page[0]->dev;
> +       struct device_node *np = dev->of_node;
Kill off the temporary variable. dev->of_node is not that long and
it's used only once.

> +       struct mipi_dsi_host *host = ps_bridge->dsi.host;
This looks a bit odd. Can you move it to the !dsi_node below and add a
small comment ?



> +       if (dsi_node) {
> +               host = of_find_mipi_dsi_host_by_node(dsi_node);
> +               of_node_put(dsi_node);
> +               if (!host) {
> +                       ret = -ENODEV;
> +                       goto err;
> +               }
> +       }
> +
} else {
    // Use XXX if there's no dsi host provided by DT
    host = ps_bridge->dsi.host;
}


> +static int ps8640_wait_rom_idle(struct ps8640 *ps_bridge)
> +{
> +       struct i2c_client *client = ps_bridge->page[0];
> +       int ret;
> +
> +       ret = ps8640_write_byte(client, PAGE2_IROM_CTRL, IROM_ENABLE);
> +       if (ret)
> +               goto exit;
> +
> +       ret = ps8640_wait_spi_ready(ps_bridge);
> +       if (ret)
> +               goto err_spi;
> +
> +       ret = ps8640_wait_spi_nobusy(ps_bridge);
> +       if (ret)
> +               goto err_spi;
> +
> +       ret = ps8640_write_byte(client, PAGE2_IROM_CTRL, IROM_DISABLE);
> +       if (ret)
> +               goto exit;
> +
> +       return 0;
> +
> +err_spi:
> +       ps8640_write_byte(client, PAGE2_IROM_CTRL, IROM_DISABLE);
> +exit:
> +       if (ret)
ret is always non zero here.

> +               dev_err(&client->dev, "wait ps8640 rom idle fail: %d\n", ret);
> +
> +       return ret;
> +}
> +
> +static int ps8640_spi_dl_mode(struct ps8640 *ps_bridge)
> +{
> +       struct i2c_client *client = ps_bridge->page[2];
> +       int ret;
> +
> +       /* switch ps8640 mode to spi dl mode */
> +       if (ps_bridge->gpio_mode_sel_n)
> +               gpiod_set_value(ps_bridge->gpio_mode_sel_n, 0);
> +
> +       /* reset spi interface */
> +       ret = ps8640_write_byte(client, PAGE2_SW_RESET,
> +                               SPI_SW_RESET | MPU_SW_RESET);
> +       if (ret)
> +               goto exit;
> +
> +       ret = ps8640_write_byte(client, PAGE2_SW_RESET, MPU_SW_RESET);
> +       if (ret)
> +               goto exit;
> +
Add "return 0;" ...

> +exit:
> +       if (ret)
... drop this check.

> +               dev_err(&client->dev, "fail reset spi interface: %d\n", ret);
> +
> +       return ret;
> +}
> +
> +static int ps8640_rom_prepare(struct ps8640 *ps_bridge)
> +{


> +       for (i = 0; i < 6; i++)
s/6/ARRAY_SIZE(enc_ctrl_code)/

> +               ps8640_write_byte(client, PAGE2_ENCTLSPI_WR, enc_ctrl_code[i]);


> +static int ps8640_write_rom(struct ps8640 *ps_bridge, const struct firmware *fw)
> +{
> +       struct i2c_client *client = ps_bridge->page[0];
> +       struct device *dev = &client->dev;
> +       struct i2c_client *client2 = ps_bridge->page[2];
> +       struct i2c_client *client7 = ps_bridge->page[7];
> +       size_t pos;
> +       u8 buf[257], rom_page_id_buf[3];
> +       int ret;
> +       u16 cpy_len;
> +
> +       ps8640_write_byte(client2, PAGE2_SPI_CFG3, I2C_TO_SPI_RESET);
> +       msleep(100);
> +       ps8640_write_byte(client2, PAGE2_SPI_CFG3, 0x00);
> +
> +       for (pos = 0; pos < fw->size; pos += cpy_len) {
> +               rom_page_id_buf[0] = PAGE2_ROMADD_BYTE1;
> +               rom_page_id_buf[1] = pos >> 8;
> +               rom_page_id_buf[2] = pos >> 16;
Reuse buf[], the stack is getting big enough already ?

> +               ret = ps8640_write_bytes(client2, rom_page_id_buf, 3);
> +               if (ret)
> +                       goto error;
> +               cpy_len = fw->size >= 256 + pos ? 256 : fw->size - pos;
cpy_len = min(256, fw->size - pos); perhaps ?

> +               buf[0] = 0;
> +               memcpy(buf + 1, fw->data + pos, cpy_len);
> +               ret = ps8640_write_bytes(client7, buf, cpy_len + 1);
> +               if (ret)
> +                       goto error;
> +
> +               dev_dbg(dev, "fw update completed %zu / %zu bytes\n", pos,
> +                       fw->size);
> +       }
> +       return 0;
> +
> +error:
> +       dev_err(dev, "failed write external flash, %d\n", ret);
> +       return ret;
> +}
> +
> +static int ps8640_spi_normal_mode(struct ps8640 *ps_bridge)
> +{
Is it that ps8640_spi_send_cmd()... 'cannot fail' in here, unlike in
ps8640_spi_dl_mode() and ps8640_rom_prepare() ? If so it might be
worth adding a line or two of comment and making
ps8640_spi_normal_mode() return void.


> +static int ps8640_load_fw(struct ps8640 *ps_bridge, const struct firmware *fw)
> +{
> +       struct i2c_client *client = ps_bridge->page[0];
> +       struct device *dev = &client->dev;
> +       int ret;
> +       bool ps8640_status_backup = ps_bridge->enabled;
> +
> +       ret = ps8640_validate_firmware(ps_bridge, fw);
> +       if (ret)
> +               return ret;
> +
> +       mutex_lock(&ps_bridge->fw_mutex);
> +       if (!ps_bridge->in_fw_update) {
> +               if (!ps8640_status_backup)
> +                       ps8640_pre_enable(&ps_bridge->bridge);
> +
> +               ret = ps8640_enter_bl(ps_bridge);
IMHO open-coding ps8640_enter_bl/ps8640_exit_bl and having the
in_fw_update manipulation visible will make things more obvious.

> +               if (ret)
> +                       goto exit;
> +       }
> +
> +       ret = ps8640_rom_prepare(ps_bridge);
> +       if (ret)
> +               goto exit;
> +
> +       ret = ps8640_write_rom(ps_bridge, fw);
> +
> +exit:
> +       if (ret)
> +               dev_err(dev, "Failed to load firmware, %d\n", ret);
> +

> +       ps8640_exit_bl(ps_bridge, fw);
> +       if (!ps8640_status_backup)
> +               ps8640_post_disable(&ps_bridge->bridge);
Why are we calling these even if we never executed
ps8640_pre_enable/ps8640_enter_bl above ?


> +static ssize_t ps8640_update_fw_store(struct device *dev,
> +                                     struct device_attribute *attr,
> +                                     const char *buf, size_t count)
> +{
> +       struct i2c_client *client = to_i2c_client(dev);
> +       struct ps8640 *ps_bridge = i2c_get_clientdata(client);
> +       const struct firmware *fw;
> +       int error;
> +
> +       error = request_firmware(&fw, PS_FW_NAME, dev);
Can the device operate without a firmware ? If not, why is the
firmware loaded so later/after user interaction (via sysfs) ? I don't
recall any other driver in DRM to use such an approach.


Regards,
Emil

Re: [PATCH 2/2 v16] drm/bridge: Add I2C based driver for ps8640 bridge

[Daniel Kurtz]

Hi Emil,

One answer inline below.  The rest I leave to Jitao...

[snip...]

On Fri, Jun 17, 2016 at 3:14 AM, Emil Velikov <emil.l.velikov@gmail.com> wrote:

>> +static ssize_t ps8640_update_fw_store(struct device *dev,
>> +                                     struct device_attribute *attr,
>> +                                     const char *buf, size_t count)
>> +{
>> +       struct i2c_client *client = to_i2c_client(dev);
>> +       struct ps8640 *ps_bridge = i2c_get_clientdata(client);
>> +       const struct firmware *fw;
>> +       int error;
>> +
>> +       error = request_firmware(&fw, PS_FW_NAME, dev);
> Can the device operate without a firmware ? If not, why is the
> firmware loaded so later/after user interaction (via sysfs) ? I don't
> recall any other driver in DRM to use such an approach.

The PS8640 has internal flash, so it should always already have a
working firmware.
This sysfs interface is useful for user space initiated field firmware updates.

Regards,
-Daniel

> Regards,
> Emil
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

Re: [PATCH 2/2 v16] drm/bridge: Add I2C based driver for ps8640 bridge

[Daniel Vetter]

On Wed, Jun 29, 2016 at 6:31 AM, Daniel Kurtz <djkurtz@chromium.org> wrote:
> On Fri, Jun 17, 2016 at 3:14 AM, Emil Velikov <emil.l.velikov@gmail.com> wrote:
>>> +static ssize_t ps8640_update_fw_store(struct device *dev,
>>> +                                     struct device_attribute *attr,
>>> +                                     const char *buf, size_t count)
>>> +{
>>> +       struct i2c_client *client = to_i2c_client(dev);
>>> +       struct ps8640 *ps_bridge = i2c_get_clientdata(client);
>>> +       const struct firmware *fw;
>>> +       int error;
>>> +
>>> +       error = request_firmware(&fw, PS_FW_NAME, dev);
>> Can the device operate without a firmware ? If not, why is the
>> firmware loaded so later/after user interaction (via sysfs) ? I don't
>> recall any other driver in DRM to use such an approach.
>
> The PS8640 has internal flash, so it should always already have a
> working firmware.
> This sysfs interface is useful for user space initiated field firmware updates.

Might be better to just do a request_firmware on driver load, and
simply proceed if it's not there. Adding a sysfs interface (which is
abi) seems way too much overkill for this imo. If you want to upgrade
the firmware you can then just drop it into the right directory, with
no further interaction needed.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

Re: [PATCH 2/2 v16] drm/bridge: Add I2C based driver for ps8640 bridge

[Enric Balletbo Serra]

2016-07-12 12:13 GMT+02:00 Daniel Vetter <daniel@ffwll.ch>:
> On Wed, Jun 29, 2016 at 6:31 AM, Daniel Kurtz <djkurtz@chromium.org> wrote:
>> On Fri, Jun 17, 2016 at 3:14 AM, Emil Velikov <emil.l.velikov@gmail.com> wrote:
>>>> +static ssize_t ps8640_update_fw_store(struct device *dev,
>>>> +                                     struct device_attribute *attr,
>>>> +                                     const char *buf, size_t count)
>>>> +{
>>>> +       struct i2c_client *client = to_i2c_client(dev);
>>>> +       struct ps8640 *ps_bridge = i2c_get_clientdata(client);
>>>> +       const struct firmware *fw;
>>>> +       int error;
>>>> +
>>>> +       error = request_firmware(&fw, PS_FW_NAME, dev);
>>> Can the device operate without a firmware ? If not, why is the
>>> firmware loaded so later/after user interaction (via sysfs) ? I don't
>>> recall any other driver in DRM to use such an approach.
>>
>> The PS8640 has internal flash, so it should always already have a
>> working firmware.
>> This sysfs interface is useful for user space initiated field firmware updates.
>
> Might be better to just do a request_firmware on driver load, and
> simply proceed if it's not there. Adding a sysfs interface (which is
> abi) seems way too much overkill for this imo. If you want to upgrade
> the firmware you can then just drop it into the right directory, with
> no further interaction needed.

IMHO I'm not sure if for this use case request_firmware on driver load
is a good idea. Flash the non-volatile internal chip can be a slow
operation and if you forget to remove the firmware after drop it into
the right directory apart from slow down the driver probe you can
damage the chip depending on the write endurance of the chip.

This sysfs interface is used on other subsystems when there is a
non-volatile memory, as example you can see at [1], [2]. Unfortunately
not all are using the same sysfs interface and maybe this should be
standardized (maybe it's an opportunity to define it)

Regards,
 Enric

[1] http://lxr.free-electrons.com/source/drivers/input/touchscreen/wdt87xx_i2c.c#L922
[2] http://lxr.free-electrons.com/source/drivers/scsi/pm8001/pm8001_ctl.c#L732


> -Daniel
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

Re: [PATCH 2/2 v16] drm/bridge: Add I2C based driver for ps8640 bridge

[Daniel Vetter]

On Thu, Aug 04, 2016 at 12:35:59PM +0200, Enric Balletbo Serra wrote:
> 2016-07-12 12:13 GMT+02:00 Daniel Vetter <daniel@ffwll.ch>:
> > On Wed, Jun 29, 2016 at 6:31 AM, Daniel Kurtz <djkurtz@chromium.org> wrote:
> >> On Fri, Jun 17, 2016 at 3:14 AM, Emil Velikov <emil.l.velikov@gmail.com> wrote:
> >>>> +static ssize_t ps8640_update_fw_store(struct device *dev,
> >>>> +                                     struct device_attribute *attr,
> >>>> +                                     const char *buf, size_t count)
> >>>> +{
> >>>> +       struct i2c_client *client = to_i2c_client(dev);
> >>>> +       struct ps8640 *ps_bridge = i2c_get_clientdata(client);
> >>>> +       const struct firmware *fw;
> >>>> +       int error;
> >>>> +
> >>>> +       error = request_firmware(&fw, PS_FW_NAME, dev);
> >>> Can the device operate without a firmware ? If not, why is the
> >>> firmware loaded so later/after user interaction (via sysfs) ? I don't
> >>> recall any other driver in DRM to use such an approach.
> >>
> >> The PS8640 has internal flash, so it should always already have a
> >> working firmware.
> >> This sysfs interface is useful for user space initiated field firmware updates.
> >
> > Might be better to just do a request_firmware on driver load, and
> > simply proceed if it's not there. Adding a sysfs interface (which is
> > abi) seems way too much overkill for this imo. If you want to upgrade
> > the firmware you can then just drop it into the right directory, with
> > no further interaction needed.
> 
> IMHO I'm not sure if for this use case request_firmware on driver load
> is a good idea. Flash the non-volatile internal chip can be a slow
> operation and if you forget to remove the firmware after drop it into
> the right directory apart from slow down the driver probe you can
> damage the chip depending on the write endurance of the chip.

Ah ok. Explaining this in the commit message would be really good.

> This sysfs interface is used on other subsystems when there is a
> non-volatile memory, as example you can see at [1], [2]. Unfortunately
> not all are using the same sysfs interface and maybe this should be
> standardized (maybe it's an opportunity to define it)

+1 on standardizing this.
-Daniel
> 
> Regards,
>  Enric
> 
> [1] http://lxr.free-electrons.com/source/drivers/input/touchscreen/wdt87xx_i2c.c#L922
> [2] http://lxr.free-electrons.com/source/drivers/scsi/pm8001/pm8001_ctl.c#L732
> 
> 
> > -Daniel
> > --
> > Daniel Vetter
> > Software Engineer, Intel Corporation
> > +41 (0) 79 365 57 48 - http://blog.ffwll.ch
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

Re: [PATCH 2/2 v16] drm/bridge: Add I2C based driver for ps8640 bridge

[Russell King - ARM Linux]

On Tue, Jul 12, 2016 at 12:13:52PM +0200, Daniel Vetter wrote:
> Might be better to just do a request_firmware on driver load, and
> simply proceed if it's not there.

That is almost never a good idea - if the driver is built-in, then
the request_firmware call happens before the real rootfs is mounted,
which makes it complicated to get the firmware delivered to the
driver.

Sure, it works nicely if the drivers are built as modules, but not
everyone wants to deal with modules and initramfs images.

If we're wanting to just update the firmware, that should be an
explicit administrative decision requiring an explicit action by the
system administrator, and not done by placing a file in some magic
location so that request_firmware() can find it, which then gets
picked up at boot time/driver load time.  Consider what could happen
if linux-firmware picks up the file and places it in the appropriate
location by default.

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