linux-kernel - Re: [PATCH v2 2/2] irqchip: Add Qualcomm MPM controller driver

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Message-ID: <e0bb6bbf-60a2-aaeb-1a3d-c174c030f8c7@quicinc.com>
Date:   Tue, 30 Nov 2021 14:24:21 +0530
From:   Maulik Shah <quic_mkshah@...cinc.com>
To:     Shawn Guo <shawn.guo@...aro.org>
CC:     Marc Zyngier <maz@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Bjorn Andersson" <bjorn.andersson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Loic Poulain <loic.poulain@...aro.org>,
        <devicetree@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] irqchip: Add Qualcomm MPM controller driver

Hi,

On 11/30/2021 2:01 PM, Shawn Guo wrote:
>>     This can be converted to read poll_timeout(). This was introduced in
>>     place of wmb() to make sure writes are completed.
> Hmm, in this case, writel() will just do the right thing, as it wraps
> wmb() there.  Or am I missing something?
>
> Shawn
#define writel(v,c)             ({ __iowmb(); writel_relaxed((v),(c)); })

writel() does not do wmb() after writel_relaxed(), it does before.

we need to make sure write is propagated, so wmb() or read  back with 
timeout need to be kept after writel() is done.

Thanks,
Maulik