Hi Simon,
On 10/17/2012 05:50 PM, Simon Glass wrote:
Hi Eric,
On Wed, Oct 17, 2012 at 5:41 PM, Eric Nelson
<eric.nel...@boundarydevices.com> wrote:
Hi Simon,
On 10/17/2012 03:07 PM, Simon Glass wrote:
Hi Eric,
On Wed, Oct 17, 2012 at 8:34 AM, Eric Nelson
<eric.nel...@boundarydevices.com> wrote:
On 10/17/2012 03:38 AM, Lukasz Majewski wrote:
<snip>
Certainly we could make the flushing more fine grained. My reasons for
not (so far) are:
1. It is simpler to flush everything (no need to figure out what part
of display has changed)
2. The performance difference is likely to be small since flushing an
already-flushed range should be fast.
From the sake of "SW engineering" I would opt for fine grained
flushing. But if it turns out, that it costs too much, we can flush
everything.
Is anybody else in a position to get some numbers about how/if
performance is better when flushing at the more granular level?
Before deciding it wasn't worth the code, I implemented granular
flushing and didn't see any noticeable degradation when just
flushing at the end of all public functions as in this patch.
http://lists.denx.de/pipermail/u-boot/2012-September/134979.html
It seems that performance is the only reason for fine-grained
cache flush operations
Also we might be talking about different things. I have taken the
approach of flushing the whole display, but only after some display
functions. We could flush only what has changed, which is what I was
referring to as 'fine-grained'. You may have meant the idea of
flushing after every function that touches the display, or a
'fine-grained' approach of only flushing after some functions.
You're right. That's what I get for chiming in quickly before
attending a customer meeting: I jump to conclusions.
I thought 'finer-grained' referred to the way Anatolij originally
did things:
http://git.denx.de/?p=u-boot.git;a=commit;h=bfd4be803bbb7d122c2e3aaf6eaf987efa8d69da
I tried to follow that lead, but it degenerated into a horrible
mess of alignment checking.
My testing shows that flushing is pretty fast, but I was reluctant to
flush after every putc() as it seemed egregiously inefficient.
I need to spend some time with the patch to figure out how you
get around cache issues for keystroke echo.
Well my less-than-lovely approach was to use puts() for all character
echo. That has a flush.
I just read through that and it makes perfect sense.
I'm anxious to test this and your CONFIG_CONSOLE_SCROLL_LINES patch
to see how it operates at 1080P.
Without the CONFIG_CONSOLE_SCROLL_LINES patch, scrolling was incredibly
slow.
Regards,
Eric
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