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

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Date:   Wed, 2 Nov 2022 13:30:45 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Will Deacon <will@...nel.org>
Cc:     Parav Pandit <parav@...dia.com>, 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,
        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 Wed, Nov 02, 2022 at 06:05:54AM +0000, Will Deacon wrote:
> 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>

Thank you!  I will apply these tags on the next rebase.

							Thanx, Paul