Re: [PATCH 2/2] drm/panel: Add Truly NT35521 panel driver

On Wed, Aug 04, 2021 at 02:09:19PM +0200, Stephan Gerhold wrote:

quoted

On Wed, Aug 04, 2021 at 04:13:52PM +0800, Shawn Guo wrote:

quoted

+ ...
+	nt_dcs_write(0xb1, 0x6c, 0x21);
+	nt_dcs_write(0xf0, 0x55, 0xaa, 0x52, 0x00, 0x00);
+	nt_dcs_write(0x35, 0x00);
+	nt_gen_write(0x11, 0x00);
+	msleep(120);
+	nt_gen_write(0x29, 0x00);
+	usleep_range(1000, 1500);
+	nt_dcs_write(0x53, 0x24);

Did you mix up "nt_dcs_write" and "nt_gen_write" here?
The nt_gen_write(0x11, 0x00); looks like MIPI_DCS_EXIT_SLEEP_MODE
and the nt_gen_write(0x29, 0x00); looks like MIPI_DCS_SET_DISPLAY_ON.

For reference you can pull your original reference DTB from Sony through
my panel driver generator: https://github.com/msm8916-mainline/linux-mdss-dsi-panel-driver-generator

Wow, very nice!  It really deserves wider spread!

quoted

It produces the following (I compiled "msm8939-kanuti_tulip.dtb"
from https://github.com/sonyxperiadev/kernel/tree/aosp/LA.BR.1.3.3_rb2.14,
not sure if that is right):

	// ...
	dsi_generic_write_seq(dsi, 0x35, 0x00);

	ret = mipi_dsi_dcs_exit_sleep_mode(dsi);
	if (ret < 0) {
		dev_err(dev, "Failed to exit sleep mode: %d\n", ret);
		return ret;
	}
	msleep(120);

	ret = mipi_dsi_dcs_set_display_on(dsi);
	if (ret < 0) {
		dev_err(dev, "Failed to set display on: %d\n", ret);
		return ret;
	}
	usleep_range(1000, 2000);

	dsi_generic_write_seq(dsi, 0x53, 0x24);

Which also suggests that generic and DCS writes are mixed up here.

Note however that you could not use the generated driver as-is,
because Sony seems to use their own display driver instead of Qualcomm's
and some things seem to be different.

I re-created the driver using your generator.  With modeling the 5v
control GPIOs with regulators and adding backlight-gpios support, the
driver works quite nicely, except the following two problems:

1) I have to drop the MIPI_DSI_MODE_LPM configuration from .update_status
   hook. Otherwise brightness did not get updated to panel.

---8<------

diff --git a/drivers/gpu/drm/panel/panel-sony-tulip-truly-nt35521.c b/drivers/gpu/drm/panel/panel-sony-tulip-truly-nt35521.c
index 31e5f942a039..eba926c6f722 100644
--- a/drivers/gpu/drm/panel/panel-sony-tulip-truly-nt35521.c
+++ b/drivers/gpu/drm/panel/panel-sony-tulip-truly-nt35521.c

@@ -420,33 +420,23 @@ static int truly_nt35521_bl_update_status(struct backlight_device *bl)
        u16 brightness = backlight_get_brightness(bl);
        int ret;
 
-       dsi->mode_flags &= ~MIPI_DSI_MODE_LPM;
-
        ret = mipi_dsi_dcs_set_display_brightness(dsi, brightness);
        if (ret < 0)
                return ret;
 
-       dsi->mode_flags |= MIPI_DSI_MODE_LPM;
-
        return 0;
 }
------>8---