linux-kernel - RE: [PATCH] irqchip: stm32: don't set rising configuration registers at init

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Date:   Thu, 7 Mar 2019 17:24:35 +0000
From:   Fabien DESSENNE <fabien.dessenne@...com>
To:     Marc Zyngier <marc.zyngier@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre TORGUE <alexandre.torgue@...com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-stm32@...md-mailman.stormreply.com" 
        <linux-stm32@...md-mailman.stormreply.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
CC:     Benjamin GAIGNARD <benjamin.gaignard@...com>
Subject: RE: [PATCH] irqchip: stm32: don't set rising configuration registers
 at init

Hi


> -----Original Message-----
> From: Marc Zyngier <marc.zyngier@....com>
> Sent: jeudi 7 mars 2019 17:40
> To: Fabien DESSENNE <fabien.dessenne@...com>; Thomas Gleixner
> <tglx@...utronix.de>; Jason Cooper <jason@...edaemon.net>; Maxime Coquelin
> <mcoquelin.stm32@...il.com>; Alexandre TORGUE
> <alexandre.torgue@...com>; linux-kernel@...r.kernel.org; linux-stm32@...md-
> mailman.stormreply.com; linux-arm-kernel@...ts.infradead.org
> Cc: Benjamin GAIGNARD <benjamin.gaignard@...com>
> Subject: Re: [PATCH] irqchip: stm32: don't set rising configuration registers at init
> 
> On 07/03/2019 16:15, Fabien Dessenne wrote:
> > The rising configuration status register (rtsr) is not banked.
> > As it is shared with the co-processor, it should not be written at
> > probe time, else the co-processor configuration will be lost.
> >
> > Signed-off-by: Fabien Dessenne <fabien.dessenne@...com>
> 
> Fixes:?
> 
> > ---
> >  drivers/irqchip/irq-stm32-exti.c | 5 -----
> >  1 file changed, 5 deletions(-)
> >
> > diff --git a/drivers/irqchip/irq-stm32-exti.c
> > b/drivers/irqchip/irq-stm32-exti.c
> > index 6edfd4b..ff8a84f 100644
> > --- a/drivers/irqchip/irq-stm32-exti.c
> > +++ b/drivers/irqchip/irq-stm32-exti.c
> > @@ -716,7 +716,6 @@ stm32_exti_chip_data *stm32_exti_chip_init(struct
> stm32_exti_host_data *h_data,
> >  	const struct stm32_exti_bank *stm32_bank;
> >  	struct stm32_exti_chip_data *chip_data;
> >  	void __iomem *base = h_data->base;
> > -	u32 irqs_mask;
> >
> >  	stm32_bank = h_data->drv_data->exti_banks[bank_idx];
> >  	chip_data = &h_data->chips_data[bank_idx]; @@ -725,10 +724,6 @@
> > stm32_exti_chip_data *stm32_exti_chip_init(struct stm32_exti_host_data
> > *h_data,
> >
> >  	raw_spin_lock_init(&chip_data->rlock);
> >
> > -	/* Determine number of irqs supported */
> > -	writel_relaxed(~0UL, base + stm32_bank->rtsr_ofst);
> > -	irqs_mask = readl_relaxed(base + stm32_bank->rtsr_ofst);
> > -
> 
> And I guess you don't need to find out the number of supported IRQs?

That's correct, this informed is useless : irqs_mask is never used (it used to be output in a log for debug purpose.and the log has been removed)


> 
> Also, a handful of lines down, you're writing again to the same register. Why isn't
> that a problem?

It's obviously a problem : another patch is missing, I am going to add it in v2.
Thanks for pointing this out!


> 
> >  	/*
> >  	 * This IP has no reset, so after hot reboot we should
> >  	 * clear registers to avoid residue
> >
> 
> Thanks,
> 
> 	M.
> --
> Jazz is not dead. It just smells funny...