Re: [PATCH 2/2] PCI: mediatek: Using chained IRQ to setup IRQ handle

[Honghui Zhang]

On Thu, 2018-05-03 at 14:05 +0100, Marc Zyngier wrote:
> On 03/05/18 10:41, Honghui Zhang wrote:
> > On Wed, 2018-05-02 at 11:09 +0100, Marc Zyngier wrote:
> >> On 02/05/18 10:41, Honghui Zhang wrote:
> >>> On Mon, 2018-04-30 at 12:03 +0100, Marc Zyngier wrote:
> >>>> Hi Zhang,
> >>>>
> >>>> On 20/04/18 06:25, honghui.zhang@xxxxxxxxxxxx wrote:
> >>>>> From: Honghui Zhang <honghui.zhang@xxxxxxxxxxxx>
> >>>>>
> >>>>> Using irq_chip solution to setup IRQs for the consistent with IRQ framework.
> >>>>>
> >>>>> Signed-off-by: Honghui Zhang <honghui.zhang@xxxxxxxxxxxx>
> >>>>> ---
> >>>>>  drivers/pci/host/pcie-mediatek.c | 192 +++++++++++++++++++++------------------
> >>>>>  1 file changed, 105 insertions(+), 87 deletions(-)
> >>>>>
> >>>>> diff --git a/drivers/pci/host/pcie-mediatek.c b/drivers/pci/host/pcie-mediatek.c
> >>>>> index c3dc549..1d9c6f1 100644
> >>>>> --- a/drivers/pci/host/pcie-mediatek.c
> >>>>> +++ b/drivers/pci/host/pcie-mediatek.c
> >>>>> @@ -11,8 +11,10 @@
> >>>>>  #include <linux/delay.h>
> >>>>>  #include <linux/iopoll.h>
> >>>>>  #include <linux/irq.h>
> >>>>> +#include <linux/irqchip/chained_irq.h>
> >>>>>  #include <linux/irqdomain.h>
> >>>>>  #include <linux/kernel.h>
> >>>>> +#include <linux/msi.h>
> >>>>>  #include <linux/of_address.h>
> >>>>>  #include <linux/of_pci.h>
> >>>>>  #include <linux/of_platform.h>
> >>>>> @@ -130,14 +132,12 @@ struct mtk_pcie_port;
> >>>>>  /**
> >>>>>   * struct mtk_pcie_soc - differentiate between host generations
> >>>>>   * @need_fix_class_id: whether this host's class ID needed to be fixed or not
> >>>>> - * @has_msi: whether this host supports MSI interrupts or not
> >>>>>   * @ops: pointer to configuration access functions
> >>>>>   * @startup: pointer to controller setting functions
> >>>>>   * @setup_irq: pointer to initialize IRQ functions
> >>>>>   */
> >>>>>  struct mtk_pcie_soc {
> >>>>>  	bool need_fix_class_id;
> >>>>> -	bool has_msi;
> >>>>>  	struct pci_ops *ops;
> >>>>>  	int (*startup)(struct mtk_pcie_port *port);
> >>>>>  	int (*setup_irq)(struct mtk_pcie_port *port, struct device_node *node);
> >>>>> @@ -161,7 +161,9 @@ struct mtk_pcie_soc {
> >>>>>   * @lane: lane count
> >>>>>   * @slot: port slot
> >>>>>   * @irq_domain: legacy INTx IRQ domain
> >>>>> + * @inner_domain: inner IRQ domain
> >>>>>   * @msi_domain: MSI IRQ domain
> >>>>> + * @lock: protect the msi_irq_in_use bitmap
> >>>>>   * @msi_irq_in_use: bit map for assigned MSI IRQ
> >>>>>   */
> >>>>>  struct mtk_pcie_port {
> >>>>> @@ -179,7 +181,9 @@ struct mtk_pcie_port {
> >>>>>  	u32 lane;
> >>>>>  	u32 slot;
> >>>>>  	struct irq_domain *irq_domain;
> >>>>> +	struct irq_domain *inner_domain;
> >>>>>  	struct irq_domain *msi_domain;
> >>>>> +	struct mutex lock;
> >>>>>  	DECLARE_BITMAP(msi_irq_in_use, MTK_MSI_IRQS_NUM);
> >>>>>  };
> >>>>>  
> >>>>> @@ -446,103 +450,122 @@ static int mtk_pcie_startup_port_v2(struct mtk_pcie_port *port)
> >>>>>  	return 0;
> >>>>>  }
> >>>>>  
> >>>>> -static int mtk_pcie_msi_alloc(struct mtk_pcie_port *port)
> >>>>> +static void mtk_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
> >>>>>  {
> >>>>> -	int msi;
> >>>>> +	struct mtk_pcie_port *port = irq_data_get_irq_chip_data(data);
> >>>>> +	phys_addr_t addr;
> >>>>>  
> >>>>> -	msi = find_first_zero_bit(port->msi_irq_in_use, MTK_MSI_IRQS_NUM);
> >>>>> -	if (msi < MTK_MSI_IRQS_NUM)
> >>>>> -		set_bit(msi, port->msi_irq_in_use);
> >>>>> -	else
> >>>>> -		return -ENOSPC;
> >>>>> +	/* MT2712/MT7622 only support 32-bit MSI addresses */
> >>>>> +	addr = virt_to_phys(port->base + PCIE_MSI_VECTOR);
> >>>>> +	msg->address_hi = 0;
> >>>>> +	msg->address_lo = lower_32_bits(addr);
> >>>>>  
> >>>>> -	return msi;
> >>>>> +	msg->data = data->hwirq;
> >>>>> +
> >>>>> +	dev_dbg(port->pcie->dev, "msi#%d address_hi %#x address_lo %#x\n",
> >>>>> +		(int)data->hwirq, msg->address_hi, msg->address_lo);
> >>>>>  }
> >>>>>  
> >>>>> -static void mtk_pcie_msi_free(struct mtk_pcie_port *port, unsigned long hwirq)
> >>>>> +static int mtk_msi_set_affinity(struct irq_data *irq_data,
> >>>>> +				   const struct cpumask *mask, bool force)
> >>>>>  {
> >>>>> -	clear_bit(hwirq, port->msi_irq_in_use);
> >>>>> +	return -EINVAL;
> >>>>>  }
> >>>>>  
> >>>>> -static int mtk_pcie_msi_setup_irq(struct msi_controller *chip,
> >>>>> -				  struct pci_dev *pdev, struct msi_desc *desc)
> >>>>> -{
> >>>>> -	struct mtk_pcie_port *port;
> >>>>> -	struct msi_msg msg;
> >>>>> -	unsigned int irq;
> >>>>> -	int hwirq;
> >>>>> -	phys_addr_t msg_addr;
> >>>>> +static struct irq_chip mtk_msi_bottom_irq_chip = {
> >>>>> +	.name			= "MTK MSI",
> >>>>> +	.irq_compose_msi_msg	= mtk_compose_msi_msg,
> >>>>> +	.irq_set_affinity	= mtk_msi_set_affinity,
> >>>>> +	.irq_mask		= pci_msi_mask_irq,
> >>>>> +	.irq_unmask	= pci_msi_unmask_irq,
> >>>>> +};
> >>>>>  
> >>>>> -	port = mtk_pcie_find_port(pdev->bus, pdev->devfn);
> >>>>> -	if (!port)
> >>>>> -		return -EINVAL;
> >>>>> +static int mtk_pcie_irq_domain_alloc(struct irq_domain *domain, unsigned int virq,
> >>>>> +				     unsigned int nr_irqs, void *args)
> >>>>> +{
> >>>>> +	struct mtk_pcie_port *port = domain->host_data;
> >>>>> +	unsigned long bit;
> >>>>>  
> >>>>> -	hwirq = mtk_pcie_msi_alloc(port);
> >>>>> -	if (hwirq < 0)
> >>>>> -		return hwirq;
> >>>>> +	WARN_ON(nr_irqs != 1);
> >>>>> +	mutex_lock(&port->lock);
> >>>>>  
> >>>>> -	irq = irq_create_mapping(port->msi_domain, hwirq);
> >>>>> -	if (!irq) {
> >>>>> -		mtk_pcie_msi_free(port, hwirq);
> >>>>> -		return -EINVAL;
> >>>>> +	bit = find_first_zero_bit(port->msi_irq_in_use, MTK_MSI_IRQS_NUM);
> >>>>> +	if (bit >= MTK_MSI_IRQS_NUM) {
> >>>>> +		mutex_unlock(&port->lock);
> >>>>> +		return -ENOSPC;
> >>>>>  	}
> >>>>>  
> >>>>> -	chip->dev = &pdev->dev;
> >>>>> -
> >>>>> -	irq_set_msi_desc(irq, desc);
> >>>>> +	__set_bit(bit, port->msi_irq_in_use);
> >>>>>  
> >>>>> -	/* MT2712/MT7622 only support 32-bit MSI addresses */
> >>>>> -	msg_addr = virt_to_phys(port->base + PCIE_MSI_VECTOR);
> >>>>> -	msg.address_hi = 0;
> >>>>> -	msg.address_lo = lower_32_bits(msg_addr);
> >>>>> -	msg.data = hwirq;
> >>>>> +	mutex_unlock(&port->lock);
> >>>>>  
> >>>>> -	pci_write_msi_msg(irq, &msg);
> >>>>> +	irq_domain_set_info(domain, virq, bit, &mtk_msi_bottom_irq_chip,
> >>>>> +			    domain->host_data, handle_simple_irq,
> >>>>
> >>>> Why don't you handle the interrupt as an edge interrupt
> >>>> (handle_edge_irq)? That's what it really is, and the fact that you use
> >>>> "handle_simple_irq" makes me think that wou're papering over some other
> >>>> issue (see below).
> >>>
> >>> Hi, Marc,
> >>>
> >>> Thanks very much for your comments.
> >>>
> >>> I guess the MSI irq is more like a level IRQ instead of edge IRQ.
> >>> When a MSI IRQ arrived, the corresponding bit of MSI status register
> >>> will be asserted and stay asserted until it's been cleared by software.
> >>
> >> There is some confusion here. The MSI itself is always edge-triggered.
> >> That's by definition, and you cannot change it. The interrupt that is
> >> used to signal that MSIs are pending (the multiplexing interrupt) can
> >> itself be level triggered (and goes low once all the MSIs have been
> >> acknowledged).
> > 
> > Hi, Marc, thanks for your comments.
> > 
> > Yes, PCIe SPEC have defined that the MSI must be edge trigged. But I'm
> > not sure whether the HW design needed to following some edge irq
> > standard. 
> 
> 
> Given that the device is writing to the MSI doorbell, this can only be
> an edge (one way to look at it is that you cannot "unwrite" something,
> so you can't drop the level).
> 
Thanks for your explain in this point of view. I will handle it as edge
IRQ in the next version.

> > In our design, when there's MSI irq trigged(which may is edge
> > trigged in hw implemented), the corresponding msi irq status bits will
> > be asserted until it's been cleared by software. It's more like that the
> > HW IP have translate the edge irq to level status. Do you think using
> > handle_level_irq or handle_simple_irq(which most of the pci host driver
> > now doing) is acceptable in this case?
> 
> This is how it is supposed to work:
> 
> Device --edge--> MSI-controller --level--> primary controller
> 
> When you're handling the MSI, it has to be edge. When handling the
> interrupt between the MSI controller and the main irqchip, this is level.
> 
> At the moment, you have handle that first interrupt as level, which is
> wrong.
> 
> > BTW, I'm still struggling in trying the handle_edge_irq solution. Seems
> > that I could not get the msi index in irq_ack callback from
> > irq_data->hwirq, the hwirq was set by pci_msi_domain_calc_hwirq() which
> > I'm still try to figure out the proper routine in my driver.
> 
> That's because you've plugged it in the wrong irqchip. Your top-level
> irqchip (the one backing the PCI domain) must be implemented with
> irq_chip_ack_parent, and you them implement the ack logic in the
> HW-specific irqchip.
> 

Thanks very much for your advise, that's exactly the mistake that I
made. Now it's works fine, I will check it again and send the next
version.

thanks.

> 	M.