Re: [PATCH v3 3/3] drm/bridge: ti-sn65dsi86: Support hotplug detection
From: Kieran Bingham
Date: Thu Mar 10 2022 - 10:26:24 EST
Quoting Kieran Bingham (2022-03-10 15:22:27)
> When the SN65DSI86 is used in DisplayPort mode, its output is likely
> routed to a DisplayPort connector, which can benefit from hotplug
> detection. Support it in such cases, with polling mode only for now.
>
> The implementation is limited to the bridge operations, as the connector
> operations are legacy and new users should use
> DRM_BRIDGE_ATTACH_NO_CONNECTOR.
>
> Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@xxxxxxxxxxxxxxxx>
> Signed-off-by: Kieran Bingham <kieran.bingham+renesas@xxxxxxxxxxxxxxxx>
> ---
> Changes since v1:
>
> - Document the no_hpd field
> - Rely on the SN_HPD_DISABLE_REG default value in the HPD case
> - Add a TODO comment regarding IRQ support
> [Kieran]
> - Fix spelling s/assrted/asserted/
> - Only enable HPD on DisplayPort connector.
> - Support IRQ based hotplug detect
>
> Changes since v2: [Kieran]
> - Use unsigned int for values read by regmap
> - Update HPD support warning message
> - Only enable OP_HPD if IRQ support enabled.
> - Only register IRQ handler during ti_sn_bridge_probe()
> - Store IRQ in the struct ti_sn65dsi86
> - Register IRQ only when !no-hpd
> - Refactor DRM_BRIDGE_OP_DETECT and DRM_BRIDGE_OP_HPD handling
>
> drivers/gpu/drm/bridge/ti-sn65dsi86.c | 142 +++++++++++++++++++++++---
> 1 file changed, 129 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> index d581c820e5d8..328a48f09f97 100644
> --- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> +++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> @@ -70,6 +70,7 @@
> #define BPP_18_RGB BIT(0)
> #define SN_HPD_DISABLE_REG 0x5C
> #define HPD_DISABLE BIT(0)
> +#define HPD_DEBOUNCED_STATE BIT(4)
> #define SN_GPIO_IO_REG 0x5E
> #define SN_GPIO_INPUT_SHIFT 4
> #define SN_GPIO_OUTPUT_SHIFT 0
> @@ -106,10 +107,24 @@
> #define SN_PWM_EN_INV_REG 0xA5
> #define SN_PWM_INV_MASK BIT(0)
> #define SN_PWM_EN_MASK BIT(1)
> +#define SN_IRQ_EN_REG 0xE0
> +#define IRQ_EN BIT(0)
> +#define SN_IRQ_HPD_REG 0xE6
> +#define IRQ_HPD_EN BIT(0)
> +#define IRQ_HPD_INSERTION_EN BIT(1)
> +#define IRQ_HPD_REMOVAL_EN BIT(2)
> +#define IRQ_HPD_REPLUG_EN BIT(3)
> +#define IRQ_HPD_PLL_UNLOCK_EN BIT(5)
> #define SN_AUX_CMD_STATUS_REG 0xF4
> #define AUX_IRQ_STATUS_AUX_RPLY_TOUT BIT(3)
> #define AUX_IRQ_STATUS_AUX_SHORT BIT(5)
> #define AUX_IRQ_STATUS_NAT_I2C_FAIL BIT(6)
> +#define SN_IRQ_HPD_STATUS_REG 0xF5
> +#define IRQ_HPD_STATUS BIT(0)
> +#define IRQ_HPD_INSERTION_STATUS BIT(1)
> +#define IRQ_HPD_REMOVAL_STATUS BIT(2)
> +#define IRQ_HPD_REPLUG_STATUS BIT(3)
> +#define IRQ_PLL_UNLOCK BIT(5)
>
> #define MIN_DSI_CLK_FREQ_MHZ 40
>
> @@ -168,6 +183,12 @@
> * @pwm_enabled: Used to track if the PWM signal is currently enabled.
> * @pwm_pin_busy: Track if GPIO4 is currently requested for GPIO or PWM.
> * @pwm_refclk_freq: Cache for the reference clock input to the PWM.
> + *
> + * @no_hpd: Disable hot-plug detection as instructed by device tree (used
> + * for instance for eDP panels whose HPD signal won't be asserted
> + * until the panel is turned on, and is thus not usable for
> + * downstream device detection).
> + * @irq: IRQ number for the device.
> */
> struct ti_sn65dsi86 {
> struct auxiliary_device bridge_aux;
> @@ -202,6 +223,9 @@ struct ti_sn65dsi86 {
> atomic_t pwm_pin_busy;
> #endif
> unsigned int pwm_refclk_freq;
> +
> + bool no_hpd;
> + int irq;
> };
>
> static const struct regmap_range ti_sn65dsi86_volatile_ranges[] = {
> @@ -316,23 +340,25 @@ static void ti_sn65dsi86_enable_comms(struct ti_sn65dsi86 *pdata)
> ti_sn_bridge_set_refclk_freq(pdata);
>
> /*
> - * HPD on this bridge chip is a bit useless. This is an eDP bridge
> - * so the HPD is an internal signal that's only there to signal that
> - * the panel is done powering up. ...but the bridge chip debounces
> - * this signal by between 100 ms and 400 ms (depending on process,
> - * voltage, and temperate--I measured it at about 200 ms). One
> + * As this is an eDP bridge, the output will be connected to a fixed
> + * panel in most systems. HPD is in that case only an internal signal
> + * to signal that the panel is done powering up. The bridge chip
> + * debounces this signal by between 100 ms and 400 ms (depending on
> + * process, voltage, and temperate--I measured it at about 200 ms). One
> * particular panel asserted HPD 84 ms after it was powered on meaning
> * that we saw HPD 284 ms after power on. ...but the same panel said
> * that instead of looking at HPD you could just hardcode a delay of
> - * 200 ms. We'll assume that the panel driver will have the hardcoded
> - * delay in its prepare and always disable HPD.
> + * 200 ms. HPD is thus a bit useless. For this type of use cases, we'll
> + * assume that the panel driver will have the hardcoded delay in its
> + * prepare and always disable HPD.
> *
> - * If HPD somehow makes sense on some future panel we'll have to
> - * change this to be conditional on someone specifying that HPD should
> - * be used.
> + * However, on some systems, the output is connected to a DisplayPort
> + * connector. HPD is needed in such cases. To accommodate both use
> + * cases, enable HPD only when requested.
> */
> - regmap_update_bits(pdata->regmap, SN_HPD_DISABLE_REG, HPD_DISABLE,
> - HPD_DISABLE);
> + if (pdata->no_hpd)
> + regmap_update_bits(pdata->regmap, SN_HPD_DISABLE_REG,
> + HPD_DISABLE, HPD_DISABLE);
>
> pdata->comms_enabled = true;
>
> @@ -1135,6 +1161,36 @@ static void ti_sn_bridge_atomic_post_disable(struct drm_bridge *bridge,
> pm_runtime_put_sync(pdata->dev);
> }
>
> +static enum drm_connector_status ti_sn_bridge_detect(struct drm_bridge *bridge)
> +{
> + struct ti_sn65dsi86 *pdata = bridge_to_ti_sn65dsi86(bridge);
> + int val;
> +
> + regmap_read(pdata->regmap, SN_HPD_DISABLE_REG, &val);
> +
> + return val & HPD_DEBOUNCED_STATE ? connector_status_connected
> + : connector_status_disconnected;
> +}
> +
> +static void ti_sn_bridge_hpd_enable(struct drm_bridge *bridge)
> +{
> + struct ti_sn65dsi86 *pdata = bridge_to_ti_sn65dsi86(bridge);
> +
> + /* The device must remain active for HPD to function */
> + pm_runtime_get_sync(pdata->dev);
> + regmap_write(pdata->regmap, SN_IRQ_HPD_REG,
> + IRQ_HPD_EN | IRQ_HPD_INSERTION_EN |
> + IRQ_HPD_REMOVAL_EN | IRQ_HPD_REPLUG_EN);
> +}
> +
> +static void ti_sn_bridge_hpd_disable(struct drm_bridge *bridge)
> +{
> + struct ti_sn65dsi86 *pdata = bridge_to_ti_sn65dsi86(bridge);
> +
> + regmap_write(pdata->regmap, SN_IRQ_HPD_REG, 0);
> + pm_runtime_put_autosuspend(pdata->dev);
> +}
> +
> static struct edid *ti_sn_bridge_get_edid(struct drm_bridge *bridge,
> struct drm_connector *connector)
> {
> @@ -1153,6 +1209,9 @@ static const struct drm_bridge_funcs ti_sn_bridge_funcs = {
> .detach = ti_sn_bridge_detach,
> .mode_valid = ti_sn_bridge_mode_valid,
> .get_edid = ti_sn_bridge_get_edid,
> + .detect = ti_sn_bridge_detect,
> + .hpd_enable = ti_sn_bridge_hpd_enable,
> + .hpd_disable = ti_sn_bridge_hpd_disable,
> .atomic_pre_enable = ti_sn_bridge_atomic_pre_enable,
> .atomic_enable = ti_sn_bridge_atomic_enable,
> .atomic_disable = ti_sn_bridge_atomic_disable,
> @@ -1223,6 +1282,34 @@ static int ti_sn_bridge_parse_dsi_host(struct ti_sn65dsi86 *pdata)
> return 0;
> }
>
> +static irqreturn_t ti_sn65dsi86_irq_handler(int irq, void *arg)
> +{
> + struct ti_sn65dsi86 *pdata = arg;
> + int ret;
> + unsigned int hpd;
> +
> + ret = regmap_read(pdata->regmap, SN_IRQ_HPD_STATUS_REG, &hpd);
> + if (ret || !hpd)
> + return IRQ_NONE;
> +
> + if (hpd & IRQ_HPD_INSERTION_STATUS)
> + drm_bridge_hpd_notify(&pdata->bridge, connector_status_connected);
> +
> + if (hpd & IRQ_HPD_REMOVAL_STATUS)
> + drm_bridge_hpd_notify(&pdata->bridge, connector_status_disconnected);
> +
> + /* When replugged, ensure we trigger a detect to update the display */
> + if (hpd & IRQ_HPD_REPLUG_STATUS)
> + drm_bridge_hpd_notify(&pdata->bridge, connector_status_disconnected);
> +
> + /* reset the status registers */
> + regmap_write(pdata->regmap, SN_IRQ_HPD_STATUS_REG,
> + IRQ_HPD_STATUS | IRQ_HPD_INSERTION_STATUS |
> + IRQ_HPD_REMOVAL_STATUS | IRQ_HPD_REPLUG_STATUS);
> +
> + return IRQ_HANDLED;
> +}
> +
> static int ti_sn_bridge_probe(struct auxiliary_device *adev,
> const struct auxiliary_device_id *id)
> {
> @@ -1236,6 +1323,14 @@ static int ti_sn_bridge_probe(struct auxiliary_device *adev,
> return PTR_ERR(pdata->next_bridge);
> }
>
> + pdata->no_hpd = of_property_read_bool(np, "no-hpd");
> + if (pdata->next_bridge->type != DRM_MODE_CONNECTOR_DisplayPort &&
> + !pdata->no_hpd) {
> + dev_warn(pdata->dev,
> + "HPD support only implemented for full DP connectors\n");
> + pdata->no_hpd = true;
> + }
> +
> ti_sn_bridge_parse_lanes(pdata, np);
>
> ret = ti_sn_bridge_parse_dsi_host(pdata);
> @@ -1247,9 +1342,29 @@ static int ti_sn_bridge_probe(struct auxiliary_device *adev,
> pdata->bridge.type = pdata->next_bridge->type == DRM_MODE_CONNECTOR_DisplayPort
> ? DRM_MODE_CONNECTOR_DisplayPort : DRM_MODE_CONNECTOR_eDP;
>
> - if (pdata->bridge.type == DRM_MODE_CONNECTOR_DisplayPort)
> + if (pdata->bridge.type == DRM_MODE_CONNECTOR_DisplayPort) {
> pdata->bridge.ops = DRM_BRIDGE_OP_EDID;
>
> + if (!pdata->no_hpd)
> + pdata->bridge.ops |= DRM_BRIDGE_OP_DETECT;
> + }
> +
> + if (!pdata->no_hpd && pdata->irq > 0) {
> + dev_err(pdata->dev, "registering IRQ %d\n", pdata->irq);
Appologies, my debug print has slipped through. This should be removed.
--
Kieran
> +
> + ret = devm_request_threaded_irq(pdata->dev, pdata->irq, NULL,
> + ti_sn65dsi86_irq_handler,
> + IRQF_ONESHOT, "sn65dsi86-irq",
> + pdata);
> + if (ret)
> + return dev_err_probe(pdata->dev, ret,
> + "Failed to register DP interrupt\n");
> +
> + /* Enable IRQ based HPD */
> + regmap_write(pdata->regmap, SN_IRQ_EN_REG, IRQ_EN);
> + pdata->bridge.ops |= DRM_BRIDGE_OP_HPD;
> + }
> +
> drm_bridge_add(&pdata->bridge);
>
> ret = ti_sn_attach_host(pdata);
> @@ -1831,6 +1946,7 @@ static int ti_sn65dsi86_probe(struct i2c_client *client,
> return -ENOMEM;
> dev_set_drvdata(dev, pdata);
> pdata->dev = dev;
> + pdata->irq = client->irq;
>
> mutex_init(&pdata->comms_mutex);
>
> --
> 2.32.0
>