RK3566恢复显示屏异常显示的方法
设备进行EMI静电测试时，LCD显示屏异常之后不能恢复，需要在软件上检测LCD是否处于工作状态，如果没有处于工作状态，则需要重启LCD。
如何确定LCD是否处于工作状态？
参照SDK docs/Common/DISPLAY路径下的Rockchip_DRM_Panel_Porting_Guide_V1.6_20190228.pdf》文档，其中3.4章节提到了如何判断MIPI-DSI外设有正常工作？瑞芯微也为此申请了专利。
drivers/gpu/drm/drm_mipi_dsi.c
kernel/include/drm/drm_mipi_dsi.h
提供了对 MIPI-DSI 外设通信的相关 API。
支持 DCS 标准 MIPI_DCS_GET_POWER_MODE(0x0A)命令的外设,可以通过读取 power_mode 来判断，函数mipi_dsi_dcs_get_power_mode() - query the display module's current power mode。mode=0x08 说 明 设 备 目 前 是 OFF 状 态，mode=0x9c,说明设备目前是 ON 状态。
驱动说明文档
# echo off > /sys/class/drm/card0-DSI-1/status
# echo on > /sys/class/drm/card0-DSI-1/status修改驱动，启动时获取power_mode
..\x3566_linux_v1.2.0\kernel\drivers\gpu\drm\panel\panel-simple.c文件，在static int panel_simple_dsi_probe(struct mipi_dsi_device *dsi)函数中增加读取液晶状态的函数：
static int panel_simple_dsi_probe(struct mipi_dsi_device *dsi)
{
struct panel_simple *panel;
struct device *dev = &dsi->dev;
const struct panel_desc_dsi *desc;
struct panel_desc_dsi *d;
const struct of_device_id *id;
int err;
u8 mode;
id = of_match_node(dsi_of_match, dsi->dev.of_node);
if (!id)
return -ENODEV;
dev_info(dev, "panel_simple_dsi_probe\n");
if (!id->data) {
d = devm_kzalloc(dev, sizeof(*d), GFP_KERNEL);
if (!d)
return -ENOMEM;
err = panel_simple_dsi_of_get_desc_data(dev, d);
if (err) {
dev_err(dev, "failed to get desc data: %d\n", err);
return err;
}
}
desc = id->data ? id->data : d;
err = panel_simple_probe(&dsi->dev, &desc->desc);
if (err < 0)
return err;
panel = dev_get_drvdata(dev);
panel->dsi = dsi;
dsi->mode_flags = desc->flags;
dsi->format = desc->format;
dsi->lanes = desc->lanes;
++ /* user add begin */
++ if(dsi)
++ {
++ err = mipi_dsi_dcs_get_power_mode( dsi, &mode);
++ dev_info( dev, "get_power_mode err=%d, mode=%02x\n", err, mode );
++ }
++ /* user add end */
err = mipi_dsi_attach(dsi);
if (err) {
struct panel_simple *panel = dev_get_drvdata(&dsi->dev);
drm_panel_remove(&panel->base);
}
return err;
}启动时没有连接屏幕，打印如下：
[root@RK356X:/]# dmesg | grep get_power_mode
[ 0.267272] panel-simple-dsi fe060000.dsi.0: get_power_mode err=-110, mode=02启动时连接了屏幕，打印如下：
[root@RK356X:/]# dmesg | grep get_power_mode
[ 0.268318] panel-simple-dsi fe060000.dsi.0: get_power_mode err=0, mode=9c设备运行过程中定时查询屏幕状态
在panel-simple.c文件中增加一个内核线程函数，每5s读取一次power_mode：
static int kthread_checkLCDstatus_func(void * data)
{
struct mipi_dsi_device *dsi = (struct mipi_dsi_device *)data;
int err;
u8 mode;
while (!kthread_should_stop())
{
err = mipi_dsi_dcs_get_power_mode( dsi, &mode);
dev_info( &dsi->dev, "get_power_mode err=%d, mode=%02x\n", err, mode );
msleep(5000);
}
return 0;
}在panel_simple_dsi_probe()函数中创建并运行checkLCDstatus_kthread线程:
static struct task_struct *checkLCDstatus_kthread = NULL;
static int panel_simple_dsi_probe(struct mipi_dsi_device *dsi)
{
struct panel_simple *panel;
struct device *dev = &dsi->dev;
const struct panel_desc_dsi *desc;
struct panel_desc_dsi *d;
const struct of_device_id *id;
int err;
u8 mode;
id = of_match_node(dsi_of_match, dsi->dev.of_node);
if (!id)
return -ENODEV;
if (!id->data) {
d = devm_kzalloc(dev, sizeof(*d), GFP_KERNEL);
if (!d)
return -ENOMEM;
err = panel_simple_dsi_of_get_desc_data(dev, d);
if (err) {
dev_err(dev, "failed to get desc data: %d\n", err);
return err;
}
}
desc = id->data ? id->data : d;
err = panel_simple_probe(&dsi->dev, &desc->desc);
if (err < 0)
return err;
panel = dev_get_drvdata(dev);
panel->dsi = dsi;
dsi->mode_flags = desc->flags;
dsi->format = desc->format;
dsi->lanes = desc->lanes;
++ /* user add begin */
++ if(dsi)
++ {
++ err = mipi_dsi_dcs_get_power_mode( dsi, &mode);
++ dev_info( dev, "get_power_mode err=%d, mode=%02x\n", err, mode );
++ checkLCDstatus_kthread = kthread_run(kthread_checkLCDstatus_func, dsi, "test_task");
++ }
++ /* user add end */
err = mipi_dsi_attach(dsi);
if (err) {
struct panel_simple *panel = dev_get_drvdata(&dsi->dev);
drm_panel_remove(&panel->base);
}
return err;
}设备运行过程中，手动复位触发LCD复位，读取的mode重9c变为了08，日志如下：
[ 118.415228] kthread is running
[ 118.418300] panel-simple-dsi fe060000.dsi.0: get_power_mode err=0, mode=9c
[ 123.535187] kthread is running
[ 123.541131] panel-simple-dsi fe060000.dsi.0: get_power_mode err=0, mode=9c
[ 128.655245] kthread is running
[ 128.664003] panel-simple-dsi fe060000.dsi.0: get_power_mode err=0, mode=08
[ 133.775156] kthread is running
[ 133.786790] panel-simple-dsi fe060000.dsi.0: get_power_mode err=0, mode=08设备运行过程中读取到power_mode为OFF状态时，重启内核
本应该只重启LCD即可，但没有合适的方法，所以直接重启系统，修改kthread_checkLCDstatus_func()函数：
static int kthread_checkLCDstatus_func(void * data)
{
struct mipi_dsi_device *dsi = (struct mipi_dsi_device *)data;
int err;
u8 mode;
while (!kthread_should_stop())
{
err = mipi_dsi_dcs_get_power_mode( dsi, &mode);
dev_info( &dsi->dev, "get_power_mode err=%d, mode=%02x\n", err, mode );
msleep(5000);
printk("panel-simple restart kernel\n");
kernel_restart(NULL); //linux kernel restart.
}
return 0;
}