linux-kernel - Re: [PATCH 1/6] genirq: generic chip: add generic irq_mask

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Message-ID: <yw1xr2xltm70.fsf@mansr.com>
Date:   Wed, 12 Jul 2017 21:49:39 +0100
From:   Måns Rullgård <mans@...sr.com>
To:     Doug Berger <opendmb@...il.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <marc.zyngier@....com>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        Sebastian Frias <sf84@...oste.net>,
        Boris Brezillon <boris.brezillon@...e-electrons.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/6] genirq: generic chip: add generic irq_mask_ack functions

Doug Berger <opendmb@...il.com> writes:

> Mans, as the author of the only existing upstream user of this code,
> should have received this as well.
>
> -Doug
>
> On 07/07/2017 12:20 PM, Doug Berger wrote:
>> The irq_gc_mask_disable_reg_and_ack() function name implies that it
>> provides the combined functions of irq_gc_mask_disable_reg() and
>> irq_gc_ack().  However, the implementation does not actually do
>> that since it writes the mask instead of the disable register. It
>> also does not maintain the mask cache which makes it inappropriate
>> to use with other masking functions.
>> 
>> In addition, commit 659fb32d1b67 ("genirq: replace irq_gc_ack() with
>> {set,clr}_bit variants (fwd)") effectively renamed irq_gc_ack() to
>> irq_gc_set_bit() so this function probably should have also been
>> renamed at that time.
>> 
>> Since this generic chip code provides three mask functions and two
>> ack functions, this commit provides generic implementations for all
>> six combinations of the mask and ack functions suitable for use
>> with the irq_mask_ack member of the struct irq_chip.
>> 
>> The '_reg' and '_bit' portions of the base function names were left
>> out of the new combined function names in an attempt to keep the
>> function name lengths manageable with the 80 character source code
>> line length while still capturing the distinct aspects of each
>> combination of functions.
>> 
>> Signed-off-by: Doug Berger <opendmb@...il.com>

Hmm, something is wrong here.  The irq_gc_mask_disable_reg_and_ack()
function writes to regs.mask, but the irq-tango driver doesn't set this
field (there is no corresponding hardware register).  Either it is never
called, or the write ends up being harmless.  I don't remember why I set
irq_mask_ack that way.

>>  /**
>> + * irq_gc_mask_disable_and_ack_set - Mask and ack pending interrupt
>> + * @d: irq_data
>> + *
>> + * Chip has separate enable/disable registers instead of a single mask
>> + * register and pending interrupt is acknowledged by setting a bit.
>> + */
>> +void irq_gc_mask_disable_and_ack_set(struct irq_data *d)
>> +{
>> +	struct irq_chip_generic *gc = irq_data_get_irq_chip_data(d);
>> +	struct irq_chip_type *ct = irq_data_get_chip_type(d);
>> +	u32 mask = d->mask;
>> +
>> +	irq_gc_lock(gc);
>> +	irq_reg_writel(gc, mask, ct->regs.disable);
>> +	*ct->mask_cache &= ~mask;
>> +	irq_reg_writel(gc, mask, ct->regs.ack);
>> +	irq_gc_unlock(gc);
>> +}

This function looks like it should probably be used instead.  I'll try
to remember to test it when I have time to fire up that hardware.

-- 
Måns Rullgård