[v1 2/2] drm/panel: ili9882t: Avoid blurred screen from fast sleep

[Cong Yang]

At present, we have found that there may be a problem of blurred
screen during fast sleep/resume. The direct cause of the blurred
screen is that the IC does not receive 0x28/0x10. Because of the
particularity of the IC, before the panel enters sleep hid must
stop scanning, i2c_hid_core_suspend before ili9882t_disable.
This doesn't look very spec-compliant. So in order to solve this
problem, the IC can handle it through the exception mechanism when
it cannot receive 0X28/0X10 command. Handling exceptions requires a reset
50ms delay. Refer to vendor detailed analysis [1].

Ilitek vendor also suggested switching the page before entering sleep to
avoid panel IC not receiving 0x28/0x10 command.

Note: 0x28 is display off, 0x10 is sleep in.

[1]: https://github.com/ILITEK-LoganLin/Document/tree/main/ILITEK_Power_Sequence

Signed-off-by: Cong Yang <yangcong5 at huaqin.corp-partner.google.com>
---
 drivers/gpu/drm/panel/panel-ilitek-ili9882t.c | 21 ++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/panel/panel-ilitek-ili9882t.c b/drivers/gpu/drm/panel/panel-ilitek-ili9882t.c
index bbfcffe65623..0a1dd987b204 100644
--- a/drivers/gpu/drm/panel/panel-ilitek-ili9882t.c
+++ b/drivers/gpu/drm/panel/panel-ilitek-ili9882t.c
@@ -423,6 +423,23 @@ static inline struct ili9882t *to_ili9882t(struct drm_panel *panel)
 	return container_of(panel, struct ili9882t, base);
 }
 
+static int ili9882t_switch_page(struct mipi_dsi_device *dsi, u8 page)
+{
+	u8 switch_cmd[] = {0x98, 0x82, 0x00};
+	int ret;
+
+	switch_cmd[2] = page;
+
+	ret = mipi_dsi_dcs_write(dsi, ILI9882T_DCS_SWITCH_PAGE, switch_cmd, 3);
+	if (ret) {
+		dev_err(&dsi->dev,
+			"error switching panel controller page (%d)\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
 static int ili9882t_enter_sleep_mode(struct ili9882t *ili)
 {
 	struct mipi_dsi_device *dsi = ili->dsi;
@@ -444,8 +461,10 @@ static int ili9882t_enter_sleep_mode(struct ili9882t *ili)
 static int ili9882t_disable(struct drm_panel *panel)
 {
 	struct ili9882t *ili = to_ili9882t(panel);
+	struct mipi_dsi_device *dsi = ili->dsi;
 	int ret;
 
+	ili9882t_switch_page(dsi, 0x00);
 	ret = ili9882t_enter_sleep_mode(ili);
 	if (ret < 0) {
 		dev_err(panel->dev, "failed to set panel off: %d\n", ret);
@@ -507,7 +526,7 @@ static int ili9882t_prepare(struct drm_panel *panel)
 	gpiod_set_value(ili->enable_gpio, 1);
 	usleep_range(1000, 2000);
 	gpiod_set_value(ili->enable_gpio, 0);
-	usleep_range(1000, 2000);
+	usleep_range(40000, 50000);
 	gpiod_set_value(ili->enable_gpio, 1);
 	usleep_range(6000, 10000);
 
-- 
2.25.1