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Date:   Tue, 31 Jul 2018 18:57:12 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Atish Patra <atish.patra@wdc.com>
Cc:     Christoph Hellwig <hch@lst.de>,
        "tglx@linutronix.de" <tglx@linutronix.de>,
        "palmer@sifive.com" <palmer@sifive.com>,
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        "marc.zyngier@arm.com" <marc.zyngier@arm.com>,
        "robh+dt@kernel.org" <robh+dt@kernel.org>,
        "mark.rutland@arm.com" <mark.rutland@arm.com>,
        "anup@brainfault.org" <anup@brainfault.org>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        "aou@eecs.berkeley.edu" <aou@eecs.berkeley.edu>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-riscv@lists.infradead.org" <linux-riscv@lists.infradead.org>,
        "shorne@gmail.com" <shorne@gmail.com>
Subject: Re: [PATCH 7/9] irqchip: add a RISC-V PLIC driver
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On Mon, Jul 30, 2018 at 08:21:33PM -0700, Atish Patra wrote:
> I found the issue. As per PLIC documentation, a hart context is a given 
> privilege mode on a given hart. Thus, cpu context ID & cpu numbers are not 
> same. Here is the PLIC register Maps in U54 core:
>
> Ref: https://static.dev.sifive.com/U54-MC-RVCoreIP.pdf
>
> Memory address for Interrupt enable
> Address
> 0x0C00-2080   Hart 1 M-mode enables
> 0x0C00 2094   End of Hart 1 M-mode enables
>
> 0x0C00-2100   Hart 1 S-mode enables
> 0x0C00-2114   End of Hart 1 S-mode enables
>
> Memory map Claim/Threshold
> Address
> 0x0C20-1000 4B 	 M-mode priority threshold
> 0x0C20-1004 4B   M-mode claim/complete
> 0x0C20-2000 4B   S-mode priority threshold
> 0x0C20-2004 4B   S-mode claim/complete
>
> The original PLIC patch was calculating based on handle->contextid which 
> will assume numbers on a HighFive Unleashed board as 2 4 6 8.
>
> In this patch, context id is assigned as cpu numbers which will be 1 2 3 4. 
> Thus it will lead to incorrect plic address access as shown below.

Indeed.  Can you try this branch, which puts back the OF contextid
parsing from the original code:

   git://git.infradead.org/users/hch/riscv.git riscv-irq-simple.2

Gitweb:

   http://git.infradead.org/users/hch/riscv.git/shortlog/refs/heads/riscv-irq-simple.2