linux-kernel - Re: [PATCH v5 3/4] riscv: Implement Zicbom-based cache management operations

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Date:   Thu, 30 Jun 2022 06:28:30 +0200
From:   Christoph Hellwig <hch@....de>
To:     Heiko Stuebner <heiko@...ech.de>
Cc:     palmer@...belt.com, paul.walmsley@...ive.com,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        wefu@...hat.com, guoren@...nel.org, cmuellner@...ux.com,
        philipp.tomsich@...ll.eu, hch@....de, samuel@...lland.org,
        atishp@...shpatra.org, anup@...infault.org, mick@....forth.gr,
        robh+dt@...nel.org, krzk+dt@...nel.org, devicetree@...r.kernel.org,
        drew@...gleboard.org, rdunlap@...radead.org,
        Atish Patra <atish.patra@....com>
Subject: Re: [PATCH v5 3/4] riscv: Implement Zicbom-based cache management
 operations

On Wed, Jun 29, 2022 at 11:59:43PM +0200, Heiko Stuebner wrote:
> The Zicbom ISA-extension was ratified in november 2021
> and introduces instructions for dcache invalidate, clean
> and flush operations.
> 
> Implement cache management operations based on them.
> 
> Of course not all cores will support this, so implement an
> alternative-based mechanism that replaces empty instructions
> with ones done around Zicbom instructions.
> 
> As discussed in previous versions, assume the platform
> being coherent by default so that non-coherent devices need
> to get marked accordingly by firmware.

The subject here seems somewhat odd.  Yes, it does implement the
low-level cache management ops, but more importantly it adds
support for devices that are not DMA coherent.

Otherwise looks good:

Reviewed-by: Christoph Hellwig <hch@....de>