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

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Message-ID: <20230329034958.GC3554086@dragon>
Date:   Wed, 29 Mar 2023 11:49:58 +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 Tue, Mar 28, 2023 at 12:02:53PM +0200, Konrad Dybcio wrote:
> The MPM hardware is accessible to us from the ARM CPUs through a shared
> memory region (RPM MSG RAM) that's also concurrently accessed by other
> kinds of cores on the system (like modem, ADSP etc.). Modeling this
> relation in a (somewhat) sane manner in the device tree basically
> requires us to either present the MPM as a child of said memory region
> (which makes little sense, as a mapped memory carveout is not a bus),
> define nodes which bleed their register spaces into one another, or
> passing their slice of the MSG RAM through some kind of a property.
> 
> Go with the third option and add a way to map a region passed through
> the "qcom,rpm-msg-ram" property as our register space.
> 
> The current way of using 'reg' is preserved for ABI reasons.
> 
> Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
> ---
>  drivers/irqchip/irq-qcom-mpm.c | 30 +++++++++++++++++++++++++-----
>  1 file changed, 25 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/irqchip/irq-qcom-mpm.c b/drivers/irqchip/irq-qcom-mpm.c
> index d30614661eea..6fe59f4deef4 100644
> --- a/drivers/irqchip/irq-qcom-mpm.c
> +++ b/drivers/irqchip/irq-qcom-mpm.c
> @@ -14,6 +14,7 @@
>  #include <linux/mailbox_client.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
> +#include <linux/of_address.h>
>  #include <linux/of_device.h>
>  #include <linux/platform_device.h>
>  #include <linux/pm_domain.h>
> @@ -322,8 +323,10 @@ static int qcom_mpm_init(struct device_node *np, struct device_node *parent)
>  	struct device *dev = &pdev->dev;
>  	struct irq_domain *parent_domain;
>  	struct generic_pm_domain *genpd;
> +	struct device_node *msgram_np;
>  	struct qcom_mpm_priv *priv;
>  	unsigned int pin_cnt;
> +	struct resource res;
>  	int i, irq;
>  	int ret;
>  
> @@ -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>;
	};

Shawn

> +		of_node_put(msgram_np);
> +		if (IS_ERR(priv->base))
> +			return PTR_ERR(priv->base);
> +	} else {
> +		/* Otherwise, fall back to simple MMIO. */
> +		priv->base = devm_platform_ioremap_resource(pdev, 0);
> +		if (IS_ERR(priv->base))
> +			return PTR_ERR(priv->base);
> +	}
>  
>  	for (i = 0; i < priv->reg_stride; i++) {
>  		qcom_mpm_write(priv, MPM_REG_ENABLE, i, 0);
> @@ -387,8 +402,10 @@ static int qcom_mpm_init(struct device_node *np, struct device_node *parent)
>  	}
>  
>  	irq = platform_get_irq(pdev, 0);
> -	if (irq < 0)
> -		return irq;
> +	if (irq < 0) {
> +		ret = irq;
> +		goto unmap_base;
> +	}
>  
>  	genpd = &priv->genpd;
>  	genpd->flags = GENPD_FLAG_IRQ_SAFE;
> @@ -451,6 +468,9 @@ static int qcom_mpm_init(struct device_node *np, struct device_node *parent)
>  	mbox_free_channel(priv->mbox_chan);
>  remove_genpd:
>  	pm_genpd_remove(genpd);
> +unmap_base:
> +	if (res.start)
> +		iounmap(priv->base);
>  	return ret;
>  }
>  
> 
> -- 
> 2.40.0
>