linux-kernel - Re: [PATCH 6/6] ARM: da850: adjust memory settings for tilcdc

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Date:   Tue, 4 Oct 2016 11:20:34 +0200
From:   Bartosz Golaszewski <bgolaszewski@...libre.com>
To:     Peter Ujfalusi <peter.ujfalusi@...com>
Cc:     Kevin Hilman <khilman@...libre.com>,
        Michael Turquette <mturquette@...libre.com>,
        Sekhar Nori <nsekhar@...com>, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Russell King <linux@...linux.org.uk>,
        LKML <linux-kernel@...r.kernel.org>,
        arm-soc <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 6/6] ARM: da850: adjust memory settings for tilcdc

2016-09-30 21:19 GMT+02:00 Peter Ujfalusi <peter.ujfalusi@...com>:
> On 09/30/2016 06:06 PM, Bartosz Golaszewski wrote:
>>
>> Just ran a quick test with speaker-test -c2 -twav. Besides the fact
>> that the left and right channels are inverted (I'm looking into that),
>> I didn't notice any problems. Even at 1024x768 resolution, playing
>> audio at the same time seems to work fine.
>

Hi Peter

> That's good to hear, but I think the priorities should be set:
> LCDC and EDMA30TC1 to highest priority
> EDMA30TC0 to priority 2
>
> The 0TC0 is used by MMC and if you want to play a video you might need the
> servicing TC to be higher priority then other masters.
>
> If audio playback would trigger sync losts in lcdc then we might need to move
> 0TC1 to priority 1.
>

Did you mean "set EDMA31TC0 to priority 2"? EDMA30TC0 is already at
the highest priority. Or did you mean that we need to lower the
EDMA30TC0 priority? In that case: is 2 the correct value? EDMA31TC0 is
used by mmc1 and its priority is 4. Shouldn't we set both to be the
same?

> I agree that LCDC priority needs to be higher, but I do wonder why the default
> (5) is not working and if it is not working why it is 5...
>
> My guess is that the change in the PBBPR register is the one actually helping
> here.
>

While it seems that lowering the EDMA30TC0 priority is indeed
unnecessary, if I don't set the LCDC master to priority 0, I still get
FIFO underflows even with the change in PBBPR.

Thanks,
Bartosz