Re: [RFC] ITS fails to allocate on rk3568/rk3566

From: Marc Zyngier <maz@kernel.org>
To: Kever Yang <kever.yang@rock-chips.com>
Cc: "Peter Geis" <pgwipeout@gmail.com>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"open list:ARM/Rockchip SoC..."
	<linux-rockchip@lists.infradead.org>,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
	"Heiko Stübner" <heiko@sntech.de>
Subject: Re: [RFC] ITS fails to allocate on rk3568/rk3566
Date: Thu, 15 Apr 2021 09:11:21 +0100	[thread overview]
Message-ID: <87k0p4m0gm.wl-maz@kernel.org> (raw)
In-Reply-To: <678e9950-dd85-abb2-a104-07a4db1fad49@rock-chips.com>

Hi Kever,

On Thu, 15 Apr 2021 08:24:33 +0100,
Kever Yang <kever.yang@rock-chips.com> wrote:
> 
> Hi Marc, Peter,
> 
>     RK356x GIC has two issues:
> 
> 1. GIC only support 32bit address while rk356x supports 8GB DDR SDRAM,
> so we use ZONE_DMA32 to fix this issue;

What transactions does this affect exactly? Only some ITS tables? Or
all of them, including the command queue? What about the configuration
and pending tables associated with the redistributors?

> 2. GIC version is r1p6-00rel0, RK356x interconnect does not support
> GIC and CPU snoop to each other, hence the GIC does not support the
> shareability feature.  The read of register value for shareability 
> feature does not return as expect in GICR and GITS, so we have to
> workaround for it.

How about the cacheability attribute? Can you please provide the exact
set of attributes that this system actually supports for each of the
ITS and redistributor base registers?

Also, please provide errata numbers for these two issues so that we
can properly document them and track the workarounds.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

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