linux-kernel - Re: [PATCH] riscv: dts: spacemit: add UART resets for Soc K1

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Message-ID: <20250820230605-GYA1065530@gentoo>
Date: Thu, 21 Aug 2025 07:06:05 +0800
From: Yixun Lan <dlan@...too.org>
To: Hendrik Hamerlinck <hendrik.hamerlinck@...mernet.be>
Cc: robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org,
	paul.walmsley@...ive.com, palmer@...belt.com, aou@...s.berkeley.edu,
	alex@...ti.fr, skhan@...uxfoundation.org,
	linux-kernel-mentees@...ts.linux.dev, devicetree@...r.kernel.org,
	linux-riscv@...ts.infradead.org, spacemit@...ts.linux.dev,
	linux-kernel@...r.kernel.org, elder@...cstar.com
Subject: Re: [PATCH] riscv: dts: spacemit: add UART resets for Soc K1

On 20:27 Wed 20 Aug     , Hendrik Hamerlinck wrote:
> Hello,
> 
> On 8/7/25 21:18, Hendrik Hamerlinck wrote:
> > Add reset control entries for all UARTs in the SpaceMIT K1 SoC Device Tree.
> > UART0 was functional as it did not need a reset. But the other UARTs were
> > unable to access their registers without the reset being applied.
> >
> > Although perhaps not needed I did add the reset for UART0 as well,
> > to ensure consistency across all UARTs. With the current-speed set to
> > 112500 baud rate, it matches the factory U-Boot settings.
> > This should not give issues with early console usage. But perhaps it could
> > be a good idea to let somebody else confirm this as well.
> I have tested this version for a while and no longer see the need for
> additional confirmation.
> 
> >
> > Tested this locally on both Orange Pi RV2 and Banana Pi BPI-F3 boards. 
> > I enabled the UART9 and was able to use it successfully.
> >
> Just a gentle reminder about this patch.
> 
> All UARTs are listed in the K1 device tree and probed by the 8250_of driver,
> but without reset lines most of them are non-functional. Adding the resets
> makes them usable when mapped to devices.
> 
that probably due to other UARTs are in assert mode by default, while
UART0 already configured by bootloader..

> This patch is limited to DTS reset handling, so UARTs are usable in the
> current state. I’m aware Alex Elder is assigned to the UART peripheral on
> the wiki and will likely handle the broader driver improvements (DMA,
> clock updates, full baud-rate support), so this should not interfere with
> that work.
> 
> Thanks for taking a look!
> 
> Kind regards,
> Hendrik
> 

-- 
Yixun Lan (dlan)