linux-kernel - Re: [PATCH 2/2] irqchip: irq-qcom-mpm: Support passing a slice of SRAM as reg space

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Date:   Thu, 30 Mar 2023 09:34:49 +0800
From:   Shawn Guo <shawn.guo@...aro.org>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH 2/2] irqchip: irq-qcom-mpm: Support passing a slice of
 SRAM as reg space

On Wed, Mar 29, 2023 at 03:30:12PM +0200, Konrad Dybcio wrote:
> >>>> @@ -374,9 +377,21 @@ static int qcom_mpm_init(struct device_node *np, struct device_node *parent)
> >>>>  
> >>>>  	raw_spin_lock_init(&priv->lock);
> >>>>  
> >>>> -	priv->base = devm_platform_ioremap_resource(pdev, 0);
> >>>> -	if (IS_ERR(priv->base))
> >>>> -		return PTR_ERR(priv->base);
> >>>> +	/* If we have a handle to an RPM message ram partition, use it. */
> >>>> +	msgram_np = of_parse_phandle(np, "qcom,rpm-msg-ram", 0);
> >>>> +	if (msgram_np) {
> >>>> +		ret = of_address_to_resource(msgram_np, 0, &res);
> >>>> +		/* Don't use devm_ioremap_resource, as we're accessing a shared region. */
> >>>> +		priv->base = ioremap(res.start, resource_size(&res));
> >>>
> >>> Are you suggesting that other cores/drivers will also need to access
> >>> the mpm slice below?
> >>>
> >>> 	apss_mpm: sram@1b8 {
> >>> 		reg = <0x1b8 0x48>;
> >>> 	};
> >> Yes, the RPM M3 core. Other slices may be accessed
> >> by any core at any time.
> > 
> > Hmm, let me reword my question.  Other than irq-qcom-mpm, is there any
> > other Linux drivers that also need to request this slice region?
> No.
> 
> > Otherwise, I do not understand why devm_ioremap_resource() cannot be
> > used.
> drivers/rpmsg/qcom_glink_rpm.c calls devm_ioremap on the entire
> RPM MSG RAM.

Can we use devm_ioremap() too instead of ioremap() here?

Shawn