Re: [PATCH] OMAPDSS: HDMI: Discard phy_tx_enabled member

On 18 June 2012 13:41, Tomi Valkeinen [off-list ref] wrote:

quoted

Explicitly maintaining HDMI phy power state using a flag is prone to
race and un-necessary when we have a zero-cost alternative of checking
the state before trying to set it.

Why would reading the value from the register be any less racy than
keeping it in memory?

Racy in the sense that h/w doesn't always hop states according to what
a "state" variable would expect it to.
Also in this case, phy_tx_enabled modification is unprotected in
ti_hdmi_4xxx_phy_disable().

BTW, coming to think about it, I am not sure what we need the
spin_lock_irqsave() protection for in hdmi_check_hpd_state() ?  It
can't control HPD gpio state change and hdmi_set_phy_pwr() seems too
expensive and is already unprotected elsewhere.

And reading from memory is probably much faster
than reading from an HDMI register, so I'm not sure what you mean with
zero-cost.

Zero-cost in terms of space and bother :)

But I guess it is simpler, so in that sense the patch is ok. But please
revise the description.

OK, will do.

Thanks.