[PATCH 05/33] gpio: add generic single-register fixed-direction GPIO driver

Russell King - ARM Linux
2016-09-02T18:56:41Z

On Fri, Sep 02, 2016 at 07:50:35PM +0200, Robert Jarzmik wrote:
> Russell King - ARM Linux <linux@armlinux.org.uk> writes:
> >> Moreover, I have a bit of homework as I also see :
> >> - no SA1111 interrupts at all, especially nothing when I insert/remove my
> >> CompactFlash card
> >> This might be an effect of pxa_cplds_irqs.c I created, I must have a look.
> >
> > Do you get other SA1111 interrupts (eg, the PS/2 interrupts) delivered?
> I see no other interrupts at all.
> Actually I see no interrupt claimed in /proc/interrupts, where I would have
> expected interrupt 305.
> cat /proc/interrupts
> CPU0
> 24: 1419 SC 8 Edge gpio-0
> 25: 0 SC 9 Edge gpio-1
> 26: 0 SC 10 Edge gpio-mux
> 38: 118 SC 22 Edge UART1
> 41: 0 SC 25 Edge DMA
> 42: 40224 SC 26 Edge ost0
> 112: 1419 GPIO 0 Edge pxa_cplds_irqs
> 307: 1419 pxa_cplds 3 Edge eth0
> 387: 0 SA1111-h Edge SA1111 PCMCIA card detect
> 388: 0 SA1111-h Edge SA1111 CF card detect
> 389: 0 SA1111-h Edge SA1111 PCMCIA BVD1
> 390: 0 SA1111-h Edge SA1111 CF BVD1
> Err: 0
>
> Actually this leads me to think that this interrupt 305 is not "requested" nor
> activated. I see in sa1111.c:506 :
> "irq_set_chained_handler_and_data(sachip->irq, sa1111_irq_handler, ..."
> This puts in the handler and data, but I don't this is "enables" the interrupt,
> right ?

It should enable the interrupt - the end of that does:

if (handle != handle_bad_irq && is_chained) {
irq_settings_set_noprobe(desc);
irq_settings_set_norequest(desc);
irq_settings_set_nothread(desc);
desc->action = &chained_action;
irq_startup(desc, true);
}

and indeed, I see that it gets enabled on Assabet. That irq_startup()
should result in the irqchip's irq_startup, irq_enable, or irq_unmask
method being called.

So, that should result in the IRQ to which the sa1111 is connected
being unmasked.

Chained interrupts don't appear in /proc/interrupts.

> I traced the code in the interrupt controller (pxa_cplds_irqs), the SA1111
> physical line is not set (even with an AT/2 keyboard connected, and I don't
> think anybody tried this AT/2 on a lubbock for a long time).

Hmm. Looking at pxa_cplds_irqs, that's trying to support the CPLD
interrupts using a very very old and inefficient technique. The
whole point of the chained interrupt system is to avoid several
overheads in the system... I'm curious why PXA moved away from that.

One of the problems is that we end up nesting irq_entry()/irq_exit()
which contains a lot of code, eg trying to run softirqs. All that
stuff is pure overhead because we'll never get to run anything like
that in this path.

I'm also very concerned that the conversion is wrong. The old code
has this comment in the irq_unmask function:

- /* the irq can be acknowledged only if deasserted, so it's done here */
- LUB_IRQ_SET_CLR &= ~(1 << lubbock_irq);

In other words, we "acknowledge" (really clear the latched status) of
the interrupt _after_ we've serviced the peripheral, not before.
The new code tries to clear down the interrupt when masking it - in
other words, before the peripheral handler has had a chance to clear
down its interrupt.

I suspect you're seeing about twice as many interrupt counts on your
ethernet interface because of this - you'll be entering the handler
once for the real interrupt, but because the clear-down was ineffective,
you end up re-entering it a second time when hopefully the peripheral
is no longer asserting the interrupt.

> The interrupt is for sure masked, and therefore the SA1111 interrupts are not
> fired. Even if they would have been enabled, the "pending interrupts register"
> doesn't show any sa1111 interrupt pending, so there is something else.

Masked where though - in the SA1111 or FPGA?

> As I don't know if "enable_irq()" in sa1111.c would be an option as I have no
> sight on sa1111.c requirements, I would take any advice here.

It shouldn't be required, as I say above, irq_set_chained_handler_and_data()
deals with unmasking the IRQ already.

> > Hmm, on Neponset with a CF card inserted, I can cat that, and it reports
> > the CIS. Any error messages in the kernel log?
> None.
> I have an ever more suprising thing.
> I tried again this morning, without changing a single line of code (excepting in
> pxa_cplds_irqs.c) nor touching the CF card, and now it really rocks !!! :
> hexdump -C /sys/class/pcmcia_socket/pcmcia_socket1/cis
> hexdump -C /sys/class/pcmcia_socket/pcmcia_socket1/cis
> 00000000 01 04 df 79 01 ff 1c 04 02 db 01 ff 18 02 df 01 |...y............|
> 00000010 20 04 45 00 01 04 15 0b 04 01 00 43 46 43 41 52 | .E........CFCAR|
> 00000020 44 00 ff 21 02 04 01 22 02 01 01 22 03 02 0c 0f |D..!..."..."....|
> 00000030 1a 05 01 03 00 02 0f 1b 08 c0 40 a1 01 55 08 00 |.......... at ..U..|
> 00000040 20 1b 06 00 01 21 b5 1e 4d 1b 0a c1 41 99 01 55 | ....!..M...A..U|
> 00000050 64 f0 ff ff 20 1b 06 01 01 21 b5 1e 4d 1b 0f c2 |d... ....!..M...|
> 00000060 41 99 01 55 ea 61 f0 01 07 f6 03 01 ee 20 1b 06 |A..U.a....... ..|
> 00000070 02 01 21 b5 1e 4d 1b 0f c3 41 99 01 55 ea 61 70 |..!..M...A..U.ap|
> 00000080 01 07 76 03 01 ee 20 1b 06 03 01 21 b5 1e 4d 14 |..v... ....!..M.|
> 00000090 00 |.|
>
> I think this proves that your patches related to lubbock pcmcia conversion to
> max1602 is fully functional !

That is good news...

> Only the interrupt part to fight a bit, and then I'll try to make a couple of
> tests on the IRDA part.

I've some patches to convert mainstone, but they're not ready yet...

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