On 08/09/2015 12:04 AM, Russell King wrote:
> The dw_hdmi enable/disable handling is particularly weak in several
> regards:
> * The hotplug interrupt could call hdmi_poweron() or hdmi_poweroff()
> while DRM is setting a mode, which could race with a mode being set.
> * Hotplug will always re-enable the phy whenever it detects an active
> hotplug signal, even if DRM has disabled the output.
>
> Resolve all of these by introducing a mutex to prevent races, and a
> state-tracking bool so we know whether DRM wishes the output to be
> enabled. We choose to use our own mutex rather than ->struct_mutex
> so that we can still process interrupts in a timely fashion.
>
> Signed-off-by: Russell King <rmk+kernel at arm.linux.org.uk>
> ---
> drivers/gpu/drm/bridge/dw_hdmi.c | 29 ++++++++++++++++++++++-------
> 1 file changed, 22 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/dw_hdmi.c
> b/drivers/gpu/drm/bridge/dw_hdmi.c
> index 7b8a4e942a71..0ee188930d26 100644
> --- a/drivers/gpu/drm/bridge/dw_hdmi.c
> +++ b/drivers/gpu/drm/bridge/dw_hdmi.c
> @@ -125,6 +125,9 @@ struct dw_hdmi {
> bool sink_is_hdmi;
> bool sink_has_audio;
>
> + struct mutex mutex; /* for state below and previous_mode */
> + bool disabled; /* DRM has disabled our bridge */
> +
> spinlock_t audio_lock;
> struct mutex audio_mutex;
> unsigned int sample_rate;
> @@ -1389,8 +1392,12 @@ static void dw_hdmi_bridge_mode_set(struct drm_bridge
> *bridge,
> {
> struct dw_hdmi *hdmi = bridge->driver_private;
>
> + mutex_lock(&hdmi->mutex);
> +
> /* Store the display mode for plugin/DKMS poweron events */
> memcpy(&hdmi->previous_mode, mode, sizeof(hdmi->previous_mode));
> +
> + mutex_unlock(&hdmi->mutex);
> }
>
> static bool dw_hdmi_bridge_mode_fixup(struct drm_bridge *bridge,
> @@ -1404,14 +1411,20 @@ static void dw_hdmi_bridge_disable(struct drm_bridge
> *bridge)
> {
> struct dw_hdmi *hdmi = bridge->driver_private;
>
> + mutex_lock(&hdmi->mutex);
> + hdmi->disabled = true;
> dw_hdmi_poweroff(hdmi);
> + mutex_unlock(&hdmi->mutex);
> }
>
> static void dw_hdmi_bridge_enable(struct drm_bridge *bridge)
> {
> struct dw_hdmi *hdmi = bridge->driver_private;
>
> + mutex_lock(&hdmi->mutex);
> dw_hdmi_poweron(hdmi);
> + hdmi->disabled = false;
> + mutex_unlock(&hdmi->mutex);
> }
>
> static void dw_hdmi_bridge_nop(struct drm_bridge *bridge)
> @@ -1534,20 +1547,20 @@ static irqreturn_t dw_hdmi_irq(int irq, void *dev_id)
> phy_int_pol = hdmi_readb(hdmi, HDMI_PHY_POL0);
>
> if (intr_stat & HDMI_IH_PHY_STAT0_HPD) {
> + hdmi_modb(hdmi, ~phy_int_pol, HDMI_PHY_HPD, HDMI_PHY_POL0);
> + mutex_lock(&hdmi->mutex);
> if (phy_int_pol & HDMI_PHY_HPD) {
> dev_dbg(hdmi->dev, "EVENT=plugin\n");
>
> - hdmi_modb(hdmi, 0, HDMI_PHY_HPD, HDMI_PHY_POL0);
> -
> - dw_hdmi_poweron(hdmi);
> + if (!hdmi->disabled)
> + dw_hdmi_poweron(hdmi);
> } else {
> dev_dbg(hdmi->dev, "EVENT=plugout\n");
>
> - hdmi_modb(hdmi, HDMI_PHY_HPD, HDMI_PHY_HPD,
> - HDMI_PHY_POL0);
> -
> - dw_hdmi_poweroff(hdmi);
> + if (!hdmi->disabled)
> + dw_hdmi_poweroff(hdmi);
Just like my reply on 08/12, I thought this could be removed, so
poweron/poweroff
would only be called with bridge->enable/bridge->disable, them maybe no need
mutex here.
Best regards,
- Yakir
> }
> + mutex_unlock(&hdmi->mutex);
> drm_helper_hpd_irq_event(hdmi->bridge->dev);
> }
>
> @@ -1617,7 +1630,9 @@ int dw_hdmi_bind(struct device *dev, struct device
> *master,
> hdmi->sample_rate = 48000;
> hdmi->ratio = 100;
> hdmi->encoder = encoder;
> + hdmi->disabled = true;
>
> + mutex_init(&hdmi->mutex);
> mutex_init(&hdmi->audio_mutex);
> spin_lock_init(&hdmi->audio_lock);
>
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