linux-kernel - Re: [PATCH v6] arm pl011 serial: support multi-irq request

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Message-ID: <2051ad6b-ba8b-8ced-b893-8e24680f800c@arm.com>
Date:   Fri, 13 Aug 2021 16:17:10 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Greg KH <gregkh@...uxfoundation.org>,
        Qian Cai <quic_qiancai@...cinc.com>
Cc:     Bing Fan <hptsfb@...il.com>, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6] arm pl011 serial: support multi-irq request

On 2021-08-13 16:04, Greg KH wrote:
> On Fri, Aug 13, 2021 at 03:08:48PM +0100, Robin Murphy wrote:
>> Hi Greg,
>>
>> On 2021-08-13 09:17, Greg KH wrote:
>>> On Fri, Aug 13, 2021 at 03:56:01PM +0800, Bing Fan wrote:
>>>>
>>>> 在 8/13/2021 15:19, Greg KH 写道:
>>>>> On Fri, Aug 13, 2021 at 11:31:30AM +0800, Bing Fan wrote:
>>>>>> From: Bing Fan <tombinfan@...cent.com>
>>>>>>
>>>>>> In order to make pl011 work better, multiple interrupts are
>>>>>> required, such as TXIM, RXIM, RTIM, error interrupt(FE/PE/BE/OE);
>>>>>> at the same time, pl011 to GIC does not merge the interrupt
>>>>>> lines(each serial-interrupt corresponding to different GIC hardware
>>>>>> interrupt), so need to enable and request multiple gic interrupt
>>>>>> numbers in the driver.
>>>>>>
>>>>>> Signed-off-by: Bing Fan <tombinfan@...cent.com>
>>>>>> ---
>>>>>>     drivers/tty/serial/amba-pl011.c | 39 +++++++++++++++++++++++++++++++--
>>>>>>     1 file changed, 37 insertions(+), 2 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
>>>>>> index e14f3378b8a0..eaac3431459c 100644
>>>>>> --- a/drivers/tty/serial/amba-pl011.c
>>>>>> +++ b/drivers/tty/serial/amba-pl011.c
>>>>>> @@ -1701,6 +1701,41 @@ static void pl011_write_lcr_h(struct uart_amba_port *uap, unsigned int lcr_h)
>>>>>>     	}
>>>>>>     }
>>>>>> +static void pl011_release_multi_irqs(struct uart_amba_port *uap, unsigned int max_cnt)
>>>>>> +{
>>>>>> +	struct amba_device *amba_dev = container_of(uap->port.dev, struct amba_device, dev);
>>>>>> +	int i;
>>>>>> +
>>>>>> +	for (i = 0; i < max_cnt; i++)
>>>>>> +		if (amba_dev->irq[i])
>>>>>> +			free_irq(amba_dev->irq[i], uap);
>>>>>> +}
>>>>>> +
>>>>>> +static int pl011_allocate_multi_irqs(struct uart_amba_port *uap)
>>>>>> +{
>>>>>> +	int ret = 0;
>>>>>> +	int i;
>>>>>> +	unsigned int virq;
>>>>>> +	struct amba_device *amba_dev = container_of(uap->port.dev, struct amba_device, dev);
>>>>>> +
>>>>>> +	pl011_write(uap->im, uap, REG_IMSC);
>>>>>> +
>>>>>> +	for (i = 0; i < AMBA_NR_IRQS; i++) {
>>>>>> +		virq = amba_dev->irq[i];
>>>>>> +		if (virq == 0)
>>>>>> +			break;
>>>>>> +
>>>>>> +		ret = request_irq(virq, pl011_int, IRQF_SHARED, dev_name(&amba_dev->dev), uap);
>>>>>> +		if (ret) {
>>>>>> +			dev_err(uap->port.dev, "request %u interrupt failed\n", virq);
>>>>>> +			pl011_release_multi_irqs(uap, i - 1);
>>>>>> +			break;
>>>>>> +		}
>>>>>> +	}
>>>>>> +
>>>>>> +	return ret;
>>>>>> +}
>>>>> This function looks identical to pl011_allocate_irq(), so what is the
>>>>> difference here?  Why is this still needed at all?  What does it do that
>>>>> is different from pl011_allocate_irq()?
>>>>
>>>> The v6-patch is based on master of
>>>> git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git, not tty-next.
>>>
>>> Always submit patches based on tty-next if you want them accepted into
>>> that tree.
>>>
>>>> As below, the pl011_allocate_irq function supports single irq request only,
>>>> which different from pl011_allocate_multi_irqs.
>>>>
>>>> static int pl011_allocate_irq(struct uart_amba_port *uap)
>>>> {
>>>>       pl011_write(uap->im, uap, REG_IMSC);
>>>>
>>>>       return request_irq(uap->port.irq, pl011_int, IRQF_SHARED, "uart-pl011",
>>>> uap);
>>>> }
>>>
>>> Ok, but that does not reflect what is in my tree to be merged for
>>> 5.15-rc1.  What is wrong with the code in there that is incorrect and
>>> needs to be changed?
>>
>> As reported by Qian Cai, it blows up on ACPI-based systems by assuming
>> port.dev is an amba_device when in fact in that situation it's a
>> platform_device. If you're able to drop the current patch from your tree
>> that would probably be the best thing to do for the moment.
> 
> I have not seen any such bug report.

It's the thread on the v5 patch that you've just replied to ;)

> If something needs to be reverted in linux-next, (i.e. in my tty-next
> branch), please let me know.  Ideally by sending a pathc to do so...

Since I'm only really involved here off the back of a drive-by review 
comment, I'll leave that up to Qian.

Cheers,
Robin.