Le mar. 23 mars 2021 à 11:42, Robert Foss robert.foss@linaro.org a écrit :
On Tue, 23 Mar 2021 at 11:01, Adrien Grassein adrien.grassein@gmail.com wrote:
Hey Robert,
Thanks for the update.
Le mar. 23 mars 2021 à 10:10, Robert Foss robert.foss@linaro.org a écrit :
Hey Adrien,
Sorry about the slow reply, but I just received the documentation from the vendor. So let's dig in to the HPD issue.
No problem :)
+static enum drm_connector_status lt8912_check_cable_status(struct lt8912 *lt) +{
int ret;unsigned int reg_val;ret = regmap_read(lt->regmap[I2C_MAIN], 0xC1, ®_val);if (ret)return connector_status_unknown;if (reg_val & BIT(7))return connector_status_connected;Register 0xc0 & BIT(7) - HPD signal after debounce Register 0xc0 & BIT(6) - HPD signal for TX HPD pad
So, if I understand well, I need to write 0xc0 & BIT(6) with 1 to enable the HPD pin.
Ah, sorry about being a bit terse.
Both bit 6 & 7 are read only, and are probably best read after an IRQ.
In my case, IRQ is not triggered at all. When reading the value of the HPD pin, I always get 1 (and no transition occurs when plugging / unplugging a cable). The HPD IRQ is done on the HDMI connector driver [5]. I think a register configuration should be done to enable the IRQ pin or maybe there is a nug in electronics. The HPD pin is linked to a 2.2k pullup resistor (maybe it's wrong)
+static int lt8912_probe(struct i2c_client *client,
const struct i2c_device_id *id)+{
static struct lt8912 *lt;int ret = 0;struct device *dev = &client->dev;lt = devm_kzalloc(dev, sizeof(struct lt8912), GFP_KERNEL);if (!lt)return -ENOMEM;lt->dev = dev;lt->i2c_client[0] = client;lt->cable_status = connector_status_unknown;lt->workq = create_workqueue("lt8912_workq");Looking at [1] and maybe even better [2], I think this polling approach is the wrong way to go. And with access to documentation, I think we should be able to sort this out.
I neither like the polling approach too. I did it to go on this issue. I will totally remove it once the HPD issue will be resolved.
Using the irq driver approach requires the interrupt pin to be configured. Pin 63 of the lt8912b is the IRQ output pin.
In order to trigger interrupts based on it, the dt-binding would need to be updated[3][4] as well as whichever DTS you're using.
The IRQ part is working well in my DTB. It test it by adding some electronics to emulate the HPD pin on the GPIO expander where the HPD pin is linked.
Looking at the dt-binding patch, it does not seem to list any interrupts. So that should be added. I think the irq support from [3] & [4] can be pretty much copied.
Then we can come back and replace the polling code with the IRQ driven code from [2].
My board uses a "max7323" GPIO expander and the HPD pin is linked to it. I test this GPIO expander by soldering a pull up resistor and an interrupt on it and an interrupt was correctly triggered in both max7323 driver and hdmi-connector; So I guess that my DTB configuration is correct. I made my DBT configuration available: - hdmi-connector node: [6] - lt8912b node: |7] - max7323 node: [8].
[1] https://github.com/torvalds/linux/blob/master/drivers/gpu/drm/bridge/analogi...
[2] https://github.com/torvalds/linux/blob/v5.11/drivers/gpu/drm/bridge/lontium-...
[3] https://github.com/torvalds/linux/blob/v5.11/Documentation/devicetree/bindin...
[4] https://github.com/torvalds/linux/blob/v5.11/Documentation/devicetree/bindin...
[5] https://github.com/torvalds/linux/blob/master/drivers/gpu/drm/bridge/display... [6] https://github.com/grassead/linux-next/blob/master/arch/arm64/boot/dts/frees... [7] https://github.com/grassead/linux-next/blob/master/arch/arm64/boot/dts/frees... [8] https://github.com/grassead/linux-next/blob/master/arch/arm64/boot/dts/frees...
Thanks,