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From:   "hasegawa-hitomi@fujitsu.com" <hasegawa-hitomi@fujitsu.com>
To:     Greg KH <gregkh@linuxfoundation.org>
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Subject: Re: [PATCH v3 1/1] soc: fujitsu: Add A64FX diagnostic interrupt
 driver
Thread-Topic: [PATCH v3 1/1] soc: fujitsu: Add A64FX diagnostic interrupt
 driver
Thread-Index: AQHYROFUWg6uBlnqVU2NIy0zBQeT5KzZYQIAgAdi+j8=
Date:   Fri, 8 Apr 2022 10:32:15 +0000
Message-ID: <OSZPR01MB7050ED8D47839EAC9B4FC5BFEBE49@OSZPR01MB7050.jpnprd01.prod.outlook.com>
References: <20220331092235.3000787-1-hasegawa-hitomi@fujitsu.com>
 <20220331092235.3000787-2-hasegawa-hitomi@fujitsu.com>
 <YkWVTEG5oFO82GPL@kroah.com>
In-Reply-To: <YkWVTEG5oFO82GPL@kroah.com>
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Hi Greg,=0A=
=0A=
> > Enable diagnostic interrupts for the A64FX.=0A=
> > This is done using a pseudo-NMI.=0A=
> =0A=
> I do not understand what this driver is, sorry.  Can you please provide m=
ore=0A=
> information in the changelog text for what this is, who would use it, and=
 how it will=0A=
> be interacted with.=0A=
=0A=
I understand. I will add a description in the next version.=0A=
=0A=
> > +config A64FX_DIAG=0A=
> > +	bool "A64FX diag driver"=0A=
> > +	depends on ARM64=0A=
> =0A=
> What about ACPI?  Shouldn't this code depend on that?=0A=
=0A=
Okey. I will make it dependent on ACPI.=0A=
=0A=
> > +	help=0A=
> > +	  Say Y here if you want to enable diag interrupt on A64FX.=0A=
> =0A=
> What is A64FX?=0A=
=0A=
A64FX is a processor designed by Fujitsu.=0A=
For the sake of clarity, I will describe it as "Fujitsu A64FX".=0A=
=0A=
> > +	  This driver uses pseudo-NMI if available.=0A=
> =0A=
> What does this mean?=0A=
=0A=
This driver uses the pseudo-NMI feature to perform diagnostic interrupts=0A=
for A64FX. However, I felt that it was superfluous to give this explanation=
=0A=
here, so I will delete this sentence.=0A=
=0A=
> > +	  If unsure, say N.=0A=
> =0A=
> No module?  Why not?=0A=
=0A=
request_nmi() is not EXPORT_SYMBOL. So this driver cannot be a module.=0A=
=0A=
> > +// SPDX-License-Identifier: GPL-2.0-only=0A=
> > +/*=0A=
> > + * A64FX diag driver.=0A=
> =0A=
> No copyright information?  Are you sure?=0A=
=0A=
I will add copyright information.=0A=
=0A=
> > +#define BMC_DIAG_INTERRUPT_STATUS_OFFSET (0x0044) #define=0A=
> > +BMC_INTERRUPT_STATUS_MASK ((1U) << 31)=0A=
> =0A=
> BIT()?=0A=
> =0A=
> > +#define BMC_DIAG_INTERRUPT_ENABLE_OFFSET (0x0040) #define=0A=
> > +BMC_INTERRUPT_ENABLE_MASK ((1U) << 31)=0A=
> =0A=
> BIT()?=0A=
=0A=
Okey, I will use BIT().=0A=
=0A=
> > +static irqreturn_t a64fx_diag_handler(int irq, void *dev_id) {=0A=
> > +	handle_sysrq('c');=0A=
> =0A=
> =0A=
> Why is this calling this sysrq call?  From an interrupt?  Why?=0A=
> =0A=
> And you are hard-coding "c", are you sure?=0A=
=0A=
As mentioned by Arnd, I only called panic () at first, but after receiving=
=0A=
his suggestion, I decided to call handle_sysrq ('c').=0A=
This driver only supports the function that causes a panic when receiving=
=0A=
a diagnostic interrupt from the outside, so "c" is coded.=0A=
Also, no data is added when a diagnostic interrupt is sent.=0A=
=0A=
> > +	if (mmsc & BMC_INTERRUPT_STATUS_MASK)=0A=
> > +		writel(BMC_INTERRUPT_STATUS_MASK, (void=0A=
> *)diag_status_reg_addr);=0A=
> =0A=
> No need to wait for the write to complete?=0A=
> =0A=
> You shouldn't have to cast diag_status_reg_addr, right?=0A=
=0A=
Due to the specifications of the machine, there is no problem even=0A=
if there is no write wait processing.=0A=
=0A=
I will remove constant and (void *). Thank you for pointing out.=0A=
=0A=
> > +		enable_irq(priv->irq);=0A=
> > +		priv->has_nmi =3D false;=0A=
> > +		dev_info(dev, "registered for IRQ %d\n", priv->irq);=0A=
> > +	} else {=0A=
> > +		enable_nmi(priv->irq);=0A=
> > +		priv->has_nmi =3D true;=0A=
> > +		dev_info(dev, "registered for NMI %d\n", priv->irq);=0A=
> =0A=
> When drivers are successful, they are quiet.  No need for the noise here.=
=0A=
=0A=
I will remove the message for a successful NMI/IRQ registration.=0A=
=0A=
Thank you.=0A=
Hitomi Hasegawa=