----- Original Message ----- From: Jakub Kiciński [mailto:moorray3@xxxxx] To: Maarten Brock [mailto:m.brock@xxxxxxxxxxxxx] Cc: linux-serial@xxxxxxxxxxxxxxx Sent: Sat, 07 Nov 2015 13:56:35 +0100 Subject: Re: [PATCH] sc16is7xx: Enable shared interrupts. > On Fri, 6 Nov 2015 16:48:20 +0100, Maarten Brock wrote: > > Enable shared interrupts for the sc16is7xx serial driver. > > > > Signed-off-by: Maarten Brock <m.brock@xxxxxxxxxxxxx> > > --- > > drivers/tty/serial/sc16is7xx.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/tty/serial/sc16is7xx.c > b/drivers/tty/serial/sc16is7xx.c > > index 72ffd0d..13f5f69 100644 > > --- a/drivers/tty/serial/sc16is7xx.c > > +++ b/drivers/tty/serial/sc16is7xx.c > > @@ -1230,7 +1230,8 @@ static int sc16is7xx_probe(struct device *dev, > > > > /* Setup interrupt */ > > ret = devm_request_irq(dev, irq, sc16is7xx_irq, > > - IRQF_ONESHOT | flags, dev_name(dev), s); > > + IRQF_SHARED | IRQF_ONESHOT | flags, > > + dev_name(dev), s); > > if (!ret) > > return 0; > > > > The reason why shared IRQs were not enabled is that we cannot read > the status register from IRQ handler and therefore cannot decide if > the interrupt was actually ours (we always return IRQ_HANDLED). Would > you consider setting the IRQF_SHARED in your device tree instead of > changing the default? Ok, I think I understand why it's difficult or impossible to read the status register from the IRQ handler. But why does that pose a problem when you always return IRQ_HANDLED? Your last remark seems to indicate it doesn't. Or would you recommend never to use shared interrupts with these devices? Btw. I tried to set it through the device tree, but that didn't seem to work. sc16is740: sc16is740@0 { compatible = "nxp,sc16is740"; <snip> interrupts = <25 0x82>; /* 0x80 for shared, 0x02 for falling */ } Maarten -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
