linux-kernel - Re: [PATCH v5] locking/memory-barriers.txt: Improve documentation for writel() example

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Date:   Wed, 2 Nov 2022 06:05:54 +0000
From:   Will Deacon <will@...nel.org>
To:     Parav Pandit <parav@...dia.com>
Cc:     bagasdotme@...il.com, arnd@...db.de, stern@...land.harvard.edu,
        parri.andrea@...il.com, peterz@...radead.org, boqun.feng@...il.com,
        npiggin@...il.com, dhowells@...hat.com, j.alglave@....ac.uk,
        luc.maranget@...ia.fr, paulmck@...nel.org, akiyks@...il.com,
        dlustig@...dia.com, joel@...lfernandes.org, corbet@....net,
        linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH v5] locking/memory-barriers.txt: Improve documentation
 for writel() example

On Thu, Oct 27, 2022 at 11:10:00PM +0300, Parav Pandit wrote:
> The cited commit describes that when using writel(), explicit wmb()
> is not needed. wmb() is an expensive barrier. writel() uses the needed
> platform specific barrier instead of wmb().
> 
> writeX() section of "KERNEL I/O BARRIER EFFECTS" already describes
> ordering of I/O accessors with MMIO writes.
> 
> Hence add the comment for pseudo code of writel() and remove confusing
> text around writel() and wmb().
> 
> commit 5846581e3563 ("locking/memory-barriers.txt: Fix broken DMA vs. MMIO ordering example")
> 
> Signed-off-by: Parav Pandit <parav@...dia.com>
> ---
> changelog:
> v4->v5:
> - Used suggested documentation update from Will
> - Added comment to the writel() pseudo code example
> - updated commit log for newer changes

Sorry for the delay on this, I'm really behind on patches at the moment.
This patch looks good to me, so thanks for doing it. You can either add
my:

Acked-by: Will Deacon <will@...nel.org>

or, since we worked on this together:

Co-developed-by: Will Deacon <will@...nel.org>
Signed-off-by: Will Deacon <will@...nel.org>

Cheers,

Will