Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <64f8f865-6a3f-118e-4080-91eb466a5acf@linaro.org>
Date:   Sat, 1 Apr 2023 14:06:54 +0200
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.9.1
Subject: Re: [PATCH 2/2] irqchip: irq-qcom-mpm: Support passing a slice of
 SRAM as reg space
To:     Shawn Guo <shawn.guo@linaro.org>
Cc:     Andy Gross <agross@kernel.org>,
        Bjorn Andersson <andersson@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Marc Zyngier <maz@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Marijn Suijten <marijn.suijten@somainline.org>,
        linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org,
        devicetree@vger.kernel.org
References: <20230328-topic-msgram_mpm-v1-0-1b788a5f5a33@linaro.org>
 <20230328-topic-msgram_mpm-v1-2-1b788a5f5a33@linaro.org>
 <20230329034958.GC3554086@dragon>
 <c42b8c24-2159-64ae-d36c-92c69274f24f@linaro.org>
 <20230329132819.GA3590215@dragon>
 <14350eba-edb6-0243-5451-2e2b7d1bd3fd@linaro.org>
 <20230330013449.GB3590215@dragon>
Content-Language: en-US
From:   Konrad Dybcio <konrad.dybcio@linaro.org>
In-Reply-To: <20230330013449.GB3590215@dragon>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Precedence: bulk


On 30.03.2023 03:34, Shawn Guo wrote:
> 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?
Hm. Yes, we totally can!

Konrad
> 
> Shawn