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

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