linux-kernel - Re: [PATCH v2] nd_blk: Remove mmio_flush

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Date:   Thu, 31 Aug 2017 14:41:16 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Robin Murphy <robin.murphy@....com>
Cc:     Ross Zwisler <ross.zwisler@...ux.intel.com>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2] nd_blk: Remove mmio_flush_range()

On Thu, Aug 31, 2017 at 4:27 AM, Robin Murphy <robin.murphy@....com> wrote:
> mmio_flush_range() suffers from a lack of clearly-defined semantics,
> and is somewhat ambiguous to port to other architectures where the
> scope of the writeback implied by "flush" and ordering might matter,
> but MMIO would tend to imply non-cacheable anyway. Per the rationale
> in 67a3e8fe9015 ("nd_blk: change aperture mapping from WC to WB"), the
> only existing use is actually to invalidate clean cache lines for
> ARCH_MEMREMAP_PMEM type mappings *without* writeback. Since the recent
> cleanup of the pmem API, that also now happens to be the exact purpose
> of arch_invalidate_pmem(), which would be a far more well-defined tool
> for the job.
>
> Rather than risk potentially inconsistent implementations of
> mmio_flush_range() for the sake of one callsite, streamline things by
> removing it entirely and instead move the ARCH_MEMREMAP_PMEM related
> definitions up to the libnvdimm level, so they can be shared by NFIT
> as well. This allows NFIT to be enabled for arm64.
>

Thanks, applied.