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Date: Thu, 10 Mar 2022 17:39:18 +0000
From: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: dri-devel@...ts.freedesktop.org, linux-renesas-soc@...r.kernel.org,
Sam Ravnborg <sam@...nborg.org>,
Douglas Anderson <dianders@...omium.org>,
linux-kernel@...r.kernel.org,
Andrzej Hajda <andrzej.hajda@...el.com>,
Neil Armstrong <narmstrong@...libre.com>,
Robert Foss <robert.foss@...aro.org>,
Jonas Karlman <jonas@...boo.se>,
Jernej Skrabec <jernej.skrabec@...il.com>,
David Airlie <airlied@...ux.ie>,
Daniel Vetter <daniel@...ll.ch>
Subject: Re: [PATCH v3 3/3] drm/bridge: ti-sn65dsi86: Support hotplug detection
Hi Laurent
Quoting Laurent Pinchart (2022-03-10 16:42:48)
> Hi Kieran,
>
> Thank you for the patch.
>
> On Thu, Mar 10, 2022 at 03:22:27PM +0000, Kieran Bingham wrote:
> > 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.
>
> Don't we support IRQ mode too now ?
Ah yes, I missed this for an update.
> > 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@...asonboard.com>
> > Signed-off-by: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
> > ---
> > 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 */
>
> s/registers/register/
Ack.
>
> > + 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);
>
> As you've noted, this should be removed.
Already gone in my tree.
>
> > +
> > + 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);
>
> Do we have a guarantee that the device isn't PM-suspended here ? Should
> this be done in the PM resume handler ?
This is tricky I fear. The ti_sn_bridge_probe() is called after the main
ti_sn65dsi86_probe(), which is where the pm resume handler would get
called first.
I moved the handler registration here, because we can't handle the IRQ
until we have the bridge set up, but if we were to enable interrupts in
the pm resume handler, it would get enabled during ti_sn65dsi86_probe()
before the handler is registered.
Now at that point nothing should fire an interrupt, but still - enabling
interrupts before the handler is registered doesn't sound good to me.
--
Kieran
>
> > + 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);
> >
>
> --
> Regards,
>
> Laurent Pinchart
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