Hey thanks for the blog @ssvb. I love to see this kind of analysis.
Next time maybe share it on the list?

Clement

> On Jan 22, 2015, at 5:05 PM, Hans de Goede <[email protected]> wrote:
> 
> Hi,
> 
> On 22-01-15 15:43, Michal Suchanek wrote:
>> Hello,
>> 
>> On 22 January 2015 at 14:26, Hans de Goede <[email protected]> wrote:
>>> Hi,
>>> 
>>> 
>>> On 22-01-15 08:30, Siarhei Siamashka wrote:
>>>> 
>>>> On Tue, 20 Jan 2015 14:16:35 +0100
>>>> Hans de Goede <[email protected]> wrote:
>>>> 
>>>>> Hi,
>>>>> 
>>>>> On 20-01-15 09:16, Siarhei Siamashka wrote:
>>>>>> 
>>>>>> On Mon, 19 Jan 2015 06:29:47 +0200
>>>>>> Siarhei Siamashka <[email protected]> wrote:
>>>>>> 
>>>>>>> On Sun, 04 Jan 2015 20:49:38 +0100
>>>>>>> Hans de Goede <[email protected]> wrote:
>>>>>>> 
>>>>>>>> Hi,
>>>>>>>> 
>>>>>>>> On 04-01-15 20:19, Michal Suchanek wrote:
>>>>>>>>> 
>>>>>>>>>      Setting magic 'reserved' hpcr bit on sun5i DEBE seems required
>>>>>>>>> for
>>>>>>>>>      smooth HDMI scanout of large frambuffer (eg. 1080p).
>>>>>>>>> 
>>>>>>>>>      This fix comes at the cost of some overall memory bandwidth so
>>>>>>>>> it
>>>>>>>>>      might be appropriate to detect a10s and only apply there (and
>>>>>>>>> not a13).
>>>>>>>> 
>>>>>>>> 
>>>>>>>> Hmm, Sairhei is the expert on this, adding him to the Cc. Sairhei,
>>>>>>>> what
>>>>>>>> do you think of the proposed change ?
>>>>>>> 
>>>>>>> 
>>>>>>> I don't have A10s hardware, so have no idea and can't test anything
>>>>>>> myself.
>>>>>>> 
>>>>>>> It would be great to have a better description of what exactly is
>>>>>>> happening before the patch. And precisely how the patch is helping.
>>>>>>> A description of the test setup and benchmark numbers would be
>>>>>>> appreciated. And it would be perfect if somebody else could reproduce
>>>>>>> the test and confirm the results.
>>>>>>> 
>>>>>>> I may try to check A20 with the bus width artificially reduced
>>>>>>> to 16 bits (not a totally unrealistic configuration, since
>>>>>>> A20-OLinuXino-LIME board exists). If sun5i and sun7i are similar
>>>>>>> enough, then the magic reserved bit may have some effect there too.
>>>>>>> But that's a different hardware either way.
>>>>>> 
>>>>>> 
>>>>>> Done these tests with A20. Ironically, now the tables have turned and
>>>>>> A10 seems to be doing a better job than A20 at low DRAM clock speeds
>>>>>> (~408MHz) and 16-bit bus width when dealing with full-hd monitors.
>>>>>> 
>>>>>> Just like Michal observed on A10s, setting 0x5031 as DEFE host port
>>>>>> config makes things much worse on A20. Overall, the test results look
>>>>>> in the following way on A20 with 16-bit DRAM clocked at 408MHz (yes,
>>>>>> none of the real boards uses such a slow DRAM setup) while running
>>>>>> lima-memtester and driving 1920x1080-32@60Hz monitor:
>>>>>> 
>>>>>> 0x1035 - The screen regularly blanks, but comes back again instantly.
>>>>>> 0x1037 - The screen regularly blanks, but comes back again instantly.
>>>>>> 0x5031 - Severe screen shaking.
>>>>>> 
>>>>>> Unlike A10, there does not seem to be any difference between using DEBE
>>>>>> or DEFE for framebuffer scanout on A20, so using DEBE has the same
>>>>>> effect as listed above. Setting the magic 'reserved' hpcr bit 1
>>>>>> (0x1037 value) does not seem to have any effect on sun7i. It is
>>>>>> great that it is apparently helping on sun5i/A10s though.
>>>>> 
>>>>> 
>>>>> Thanks for running these tests, this makes me more confident that I
>>>>> only need to enable DEFE in u-boot on A10, and can directly use
>>>>> DEBE on the others.
>>>> 
>>>> 
>>>> But what about A10s? Do we want to do something about it?
>>> 
>>> 
>>> Once we have some feedback from hramrach from running tests with /
>>> without the frontend enabled, then yes, unless the fix is to simple
>>> disable the frontend, and then u-boot probably is fine as is.
>> 
>> I need to re-test this but it seemed that on my a10s board enabling
>> and disabling scaler had pretty much no impact on display performance.
>> Increasing the priority of the display ports did not seem to increase
>> display performance either. However, setting the 'magic' bit degraded
>> memory throughput as reported by the lima-memspeed somewhat but
>> enabled jump-free lima-memtester rotating cube. Since a13 has no hdmi
>> this is moot for most sun5i hardware.
>> 
>> Affected would be the obsolete olinuxinos and a few HDMI sticks that
>> actually had a10s in them.
> 
> There are actually a lot of a10s using HDMI sticks out there (all later
> mk802 models use the a10s + many others) as well as various a10s
> based top setboxes and an a10s variant of the mini-x. So I would really
> like to get this fixed, I'm ok with applying your fix, but before that
> I would like to see the following confirmed:
> 
> 1) That currently you are using the scaler, since your patch modifies
> the scaler dram prio anything else would make no sense
> 
> 2) Please retest without the scalar, and if you've the same problem
> try applying the same fix / DRAM settings to the DEBE dram prio
> bits. See 
> http://ssvb.github.io/2014/11/11/revisiting-fullhd-x11-desktop-performance-of-the-allwinner-a10.html
>  
> <http://ssvb.github.io/2014/11/11/revisiting-fullhd-x11-desktop-performance-of-the-allwinner-a10.html>
> for a list of which dram prio config word is what.
> 
> Thanks,
> 
> Hans
> 
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