From: Marc Zyngier <maz@kernel.org>
To: Maulik Shah <quic_mkshah@quicinc.com>
Cc: Shawn Guo <shawn.guo@linaro.org>,
Thomas Gleixner <tglx@linutronix.de>,
Bjorn Andersson <bjorn.andersson@linaro.org>,
Rob Herring <robh+dt@kernel.org>,
Loic Poulain <loic.poulain@linaro.org>,
<devicetree@vger.kernel.org>, <linux-arm-msm@vger.kernel.org>,
<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 2/2] irqchip: Add Qualcomm MPM controller driver
Date: Tue, 30 Nov 2021 08:47:52 +0000 [thread overview]
Message-ID: <87k0gqm3lz.wl-maz@kernel.org> (raw)
In-Reply-To: <2e821841-a921-3fda-9ee6-3d5127653033@quicinc.com>
On Tue, 30 Nov 2021 07:49:48 +0000,
Maulik Shah <quic_mkshah@quicinc.com> wrote:
>
> [1 <text/plain; UTF-8 (7bit)>]
> Hi Shawn,
>
> On 11/30/2021 8:01 AM, Shawn Guo wrote:
> >>>>> + do {
> >>>>> + r_val = readl(priv->base + offset);
> >>>>> + udelay(5);
> >>>>> + } while (r_val != val);
> >>>> What? Is this waiting for a bit to clear? Why isn't this one of the
> >>>> read*_poll_timeout*() function instead? Surely you can't wait forever
> >>>> here.
> >>> This is taken from downstream, and it seems to double check the written
> >>> value by reading it back. But to be honest, I'm not really this is
> >>> necessary. I will do some testing with the read-back check dropped.
> >> How about asking for specs instead? There are QC people on Cc, and
> >> many more reading the list. Hopefully they can explain what this is
> >> all about.
> > Maulik,
> >
> > If you have some information about this, that would be great.
>
> This can be converted to read poll_timeout(). This was introduced in
> place of wmb() to make sure writes are completed.
A string of reads isn't equivalent to a dsb(st). If there is a
requirement for the write to complete, then use the required barrier.
M.
--
Without deviation from the norm, progress is not possible.
next prev parent reply other threads:[~2021-11-30 8:47 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-26 9:35 [PATCH v2 0/2] Add Qualcomm MPM irqchip driver support Shawn Guo
2021-11-26 9:35 ` [PATCH v2 1/2] dt-bindings: interrupt-controller: Add Qualcomm MPM support Shawn Guo
2021-12-01 23:02 ` Rob Herring
2021-11-26 9:35 ` [PATCH v2 2/2] irqchip: Add Qualcomm MPM controller driver Shawn Guo
2021-11-26 15:13 ` Marc Zyngier
2021-11-26 19:19 ` Marc Zyngier
2021-11-29 13:33 ` Shawn Guo
2021-11-29 15:24 ` Marc Zyngier
2021-11-30 2:31 ` Shawn Guo
2021-11-30 8:42 ` Marc Zyngier
2021-11-30 9:17 ` Shawn Guo
2021-11-30 10:44 ` Marc Zyngier
2021-12-01 7:36 ` Shawn Guo
[not found] ` <2e821841-a921-3fda-9ee6-3d5127653033@quicinc.com>
2021-11-30 8:31 ` Shawn Guo
2021-11-30 8:52 ` Marc Zyngier
2021-11-30 8:54 ` Maulik Shah
2021-11-30 8:47 ` Marc Zyngier [this message]
2021-11-27 7:49 ` kernel test robot
2021-11-29 7:23 ` Maulik Shah
2021-11-29 13:45 ` Shawn Guo
2021-11-30 8:26 ` Maulik Shah
2021-11-30 8:44 ` Shawn Guo
2021-11-30 9:04 ` Maulik Shah
2021-11-30 9:26 ` Shawn Guo
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