On Mon, May 2, 2016 at 12:56 PM, Thierry Reding thierry.reding@gmail.com wrote:

On Fri, Apr 29, 2016 at 08:04:09AM -0400, Rob Clark wrote:

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On Fri, Apr 29, 2016 at 1:32 AM, Vinay Simha simhavcs@gmail.com wrote:

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hi,

In nx7, backlight brightness control is controlled by dcs commands of MIPI_DCS_SET_DISPLAY_BRIGHTNESS. there is no PWM going to panel interface directly as we have in ifc6410/nx5

afaiu it is not uncommon to need to control backlight via panel (ie, I think basically all adaptive-backlight panels). I think the answer is for these panels, the panel driver would register it's own backlight driver, rather than get a (pwm, etc) backlight via dt bindings.

Yes, that'd be my recommendation as well.

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Possibly if the backlight commands are standardized enough then we could implement a single drm_panel_dsi_backlight helper which could be created by any of the dsi adaptive-backlight panels (ie. pass in a 'struct mipi_dsi_device *').. something like:

struct drm_panel_dsi_backlight { struct mipi_panel_dsi_device *link; ... }

struct backlight_device *drm_panel_create_dsi_backlight(struct mipi_panel_dsi_device *link) { struct drm_panel_dsi_backlight *dsi_bl; ... return devm_backlight_device_register(&link->dev, ..., dsi_bl, dsi_bl_ops, props); }

struct backlight_device *devm_backlight_device_register(struct device *dev, const char *name, struct device *parent, void *devdata, const struct backlight_ops *ops, const struct backlight_properties *props)

struct device *dev = &jdi->dsi->dev;

devm_backlight_device_register( dev, dev_name(dev), dev, jdi, &dsi_bl_ops, &props);

Here does the parent also should be jdi->dsi->dev ? because the backlight is not mapped to fb of android ( android-> settings->brightness) , even though i can change the brightness value from sysfs and it works only when the display is off. When it awakes(power button press) panel_enable calls, backlight_update_status will have the latest brightness value.

if echo the brightness value when the display is awake, dsi fails for brightness control. echo 100 > /sys/class/backlight/4700000.qcom,mdss_dsi.0/brightness [ 152.865949] dsi_cmds2buf_tx: cmd dma tx failed, type=0x15, data0=0x51, len=4

static int dsi_bl_update_status(struct backlight_device *bl) { struct jdi_panel *jdi = bl_get_data(bl); struct mipi_dsi_device *dsi = jdi->dsi; int ret; u8 brightness = bl->props.brightness;

ret = mipi_dsi_dcs_write(dsi, MIPI_DCS_SET_DISPLAY_BRIGHTNESS, &brightness, sizeof(brightness)); if (ret < 0) return ret;

return 0; }

static const struct backlight_ops dsi_bl_ops = { .update_status = dsi_bl_update_status, };

john, for android fb do we need to map the backlight in userspace? As i have seen in 3.4 kernel when we register the backlight using platform_device_register, backlight used to map with the userspace(ubuntu/fedora) settings->brightness.

I agree it would make sense to have a DCS specific helper for backlight. I'm somewhat sceptical about the standardization, even though these seem to be part of DCS 1.3. But perhaps we can start by being optimistic.

Thierry