Re: [PATCH 2/3] drm/ingenic: Reset pixclock rate when parent clock rate changes

Quoting Paul Cercueil (2020-09-25 05:29:12)

...

...

+static int ingenic_drm_update_pixclk(struct notifier_block *nb,

•                            unsigned long action,
  

•                            void *data)
  

+{

• struct ingenic_drm *priv = drm_nb_get_priv(nb);
• switch (action) {
• case PRE_RATE_CHANGE:

•       mutex_lock(&priv->clk_mutex);
  

•       priv->update_clk_rate = true;
  

•       drm_crtc_wait_one_vblank(&priv->crtc);
  

•       return NOTIFY_OK;
  

• default:

•       mutex_unlock(&priv->clk_mutex);
  

Any risk the POST_RATE_CHANGE or ABORT_RATE_CHANGE may go missing so we fail to unlock the mutex? I think not but wanted to make sure you had thought about it.

My assumption was that you always get POST_RATE_CHANGE or ABORT_RATE_CHANGE. But I am not 100% sure about that.

Michael, Stephen: is it safe to assume that I will always get notified with POST_RATE_CHANGE or ABORT_RATE_CHANGE, after I got notified with PRE_RATE_CHANGE?

I think one or the other will happen. Of course, the notifiers are sort of shunned so if you can avoid using notifiers entirely it would be better.