linux-kernel - Re: [PATCH v2] arm64: dts: rockchip: add rk3399 UART DMAs

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Message-ID: <2e5a1468-9a65-9cc5-f96c-272faeb92ec9@arm.com>
Date:   Thu, 11 Apr 2019 20:17:36 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Heiko Stuebner <heiko@...ech.de>
Cc:     Katsuhiro Suzuki <katsuhiro@...suster.net>,
        linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2] arm64: dts: rockchip: add rk3399 UART DMAs

On 2019-04-11 2:48 pm, Robin Murphy wrote:
> On 11/04/2019 13:46, Heiko Stuebner wrote:
>> Hi Robin,
>>
>> Am Samstag, 30. März 2019, 00:24:16 CEST schrieb Robin Murphy:
>>> On 2019-03-27 12:00 pm, Heiko Stuebner wrote:
>>>> Hi,
>>>>
>>>> Am Dienstag, 26. März 2019, 14:49:16 CET schrieb Katsuhiro Suzuki:
>>>>> Hello Robin,
>>>>>
>>>>> Sorry for inconvenience. Since I don't adhere enabling DMA for UARTs,
>>>>> please revert my patch if you need.
>>>>
>>>> I've dropped the patch from my queue now.
>>>>
>>>>> BTW, there are DMA properties in RK3328 device-tree like as this 
>>>>> patch.
>>>>> RK3328 UART DMA could not work correctly too...??
>>>>
>>>> I remember Rockcihip dma-controllers having issues with burst-sizes
>>>> and flushing (there is a no-flushp option in pl330), so it's
>>>> possible that all share the same error up to rk3399 and rk3328
>>>>
>>>> But so far no-one has shouted regarding the rk3328.
>>>
>>> Let me be the first, then, I guess :)
>>>
>>> I found an easy way to observe the problem on my 3399, and I've just
>>> fired up my 3328 box with a 5.0 distro kernel to find that it behaves
>>> the same. Basically just dump a large pile of text into 'less' on the
>>> serial console, and scroll through line-by-line - certain lines get
>>> dropped except for a few characters at the end.
>>>
>>> I'll see if I can narrow it down a bit, starting with trying
>>> broken-flushp...
>>
>> did you manage to find time for that test you wanted to do?
> 
> Sadly not - I got somewhat distracted by the ethernet thing, and since 
> then I've had too much else going on to follow up on any of my 'for fun' 
> projects :(

Urgh, and it turns out what I thought were dropped characters seems to 
just be my console handling line wrapping weirdly, so now I have no idea 
if RK3328 actually has an issue, and coming up with a reliable 
reproducer for RK3399 is going to take some thought...

Robin.