Subject: Re: [PATCH v3 04/11] PCI: designware-ep: Modify MSI and MSIX CAP way of finding

From: Andrew Murray <[email-masked]>
Date: Mon, 2 Sep 2019 16:07:21 +0100

On Mon, Sep 02, 2019 at 11:17:09AM +0800, Xiaowei Bao wrote:
> Each PF of EP device should have it's own MSI or MSIX capabitily
> struct, so create a dw_pcie_ep_func struct and remover the msi_cap

remover?

> and msix_cap to this struce, and manage the PFs with a list.

struce?

> 
> Signed-off-by: Xiaowei Bao <[email-masked]>
> ---
> v1:
>  - This is a new patch, to fix the issue of MSI and MSIX CAP way of
>    finding.
> v2:
>  - No change.
> v3:
>  - No change.

This makes it look like you introduced the patch in v1 and haven't
changed it since.

I think it's more common to have a history like this:

---
v3:
 - Introduced new patch, to fix the issue of MSI and MSIX CAP way of
   finding.

> 
>  drivers/pci/controller/dwc/pcie-designware-ep.c | 135 +++++++++++++++++++++---
>  drivers/pci/controller/dwc/pcie-designware.h    |  18 +++-
>  2 files changed, 134 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
> index c3bc7bd..144eb12 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-ep.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
> @@ -19,6 +19,19 @@ void dw_pcie_ep_linkup(struct dw_pcie_ep *ep)
>  	pci_epc_linkup(epc);
>  }
>  
> +struct dw_pcie_ep_func *
> +dw_pcie_ep_get_func_from_ep(struct dw_pcie_ep *ep, u8 func_no)
> +{
> +	struct dw_pcie_ep_func *ep_func;
> +
> +	list_for_each_entry(ep_func, &ep->func_list, list) {
> +		if (ep_func->func_no == func_no)
> +			return ep_func;
> +	}
> +
> +	return NULL;
> +}
> +
>  static unsigned int dw_pcie_ep_func_select(struct dw_pcie_ep *ep, u8 func_no)
>  {
>  	unsigned int func_offset = 0;
> @@ -59,6 +72,47 @@ void dw_pcie_ep_reset_bar(struct dw_pcie *pci, enum pci_barno bar)
>  		__dw_pcie_ep_reset_bar(pci, func_no, bar, 0);
>  }
>  
> +static u8 __dw_pcie_ep_find_next_cap(struct dw_pcie_ep *ep, u8 func_no,
> +		u8 cap_ptr, u8 cap)
> +{
> +	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
> +	unsigned int func_offset = 0;
> +	u8 cap_id, next_cap_ptr;
> +	u16 reg;
> +
> +	if (!cap_ptr)
> +		return 0;
> +
> +	func_offset = dw_pcie_ep_func_select(ep, func_no);
> +
> +	reg = dw_pcie_readw_dbi(pci, func_offset + cap_ptr);
> +	cap_id = (reg & 0x00ff);
> +
> +	if (cap_id > PCI_CAP_ID_MAX)
> +		return 0;
> +
> +	if (cap_id == cap)
> +		return cap_ptr;
> +
> +	next_cap_ptr = (reg & 0xff00) >> 8;
> +	return __dw_pcie_ep_find_next_cap(ep, func_no, next_cap_ptr, cap);
> +}

Which tree have you based this patchset on? v5.3-rc3 and pci/dwc both already
have this function (without the func_no). See beb4641a787d
("PCI: dwc: Add MSI-X callbacks handler").

> +
> +static u8 dw_pcie_ep_find_capability(struct dw_pcie_ep *ep, u8 func_no, u8 cap)
> +{
> +	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
> +	unsigned int func_offset = 0;
> +	u8 next_cap_ptr;
> +	u16 reg;
> +
> +	func_offset = dw_pcie_ep_func_select(ep, func_no);
> +
> +	reg = dw_pcie_readw_dbi(pci, func_offset + PCI_CAPABILITY_LIST);
> +	next_cap_ptr = (reg & 0x00ff);
> +
> +	return __dw_pcie_ep_find_next_cap(ep, func_no, next_cap_ptr, cap);
> +}
> +
>  static int dw_pcie_ep_write_header(struct pci_epc *epc, u8 func_no,
>  				   struct pci_epf_header *hdr)
>  {
> @@ -246,13 +300,18 @@ static int dw_pcie_ep_get_msi(struct pci_epc *epc, u8 func_no)
>  	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
>  	u32 val, reg;
>  	unsigned int func_offset = 0;
> +	struct dw_pcie_ep_func *ep_func;
>  
> -	if (!ep->msi_cap)
> +	ep_func = dw_pcie_ep_get_func_from_ep(ep, func_no);
> +	if (!ep_func)
> +		return -EINVAL;
> +
> +	if (!ep_func->msi_cap)
>  		return -EINVAL;
>  
>  	func_offset = dw_pcie_ep_func_select(ep, func_no);
>  
> -	reg = ep->msi_cap + func_offset + PCI_MSI_FLAGS;
> +	reg = ep_func->msi_cap + func_offset + PCI_MSI_FLAGS;
>  	val = dw_pcie_readw_dbi(pci, reg);
>  	if (!(val & PCI_MSI_FLAGS_ENABLE))
>  		return -EINVAL;
> @@ -268,13 +327,18 @@ static int dw_pcie_ep_set_msi(struct pci_epc *epc, u8 func_no, u8 interrupts)
>  	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
>  	u32 val, reg;
>  	unsigned int func_offset = 0;
> +	struct dw_pcie_ep_func *ep_func;
> +
> +	ep_func = dw_pcie_ep_get_func_from_ep(ep, func_no);
> +	if (!ep_func)
> +		return -EINVAL;
>  
> -	if (!ep->msi_cap)
> +	if (!ep_func->msi_cap)
>  		return -EINVAL;
>  
>  	func_offset = dw_pcie_ep_func_select(ep, func_no);
>  
> -	reg = ep->msi_cap + func_offset + PCI_MSI_FLAGS;
> +	reg = ep_func->msi_cap + func_offset + PCI_MSI_FLAGS;
>  	val = dw_pcie_readw_dbi(pci, reg);
>  	val &= ~PCI_MSI_FLAGS_QMASK;
>  	val |= (interrupts << 1) & PCI_MSI_FLAGS_QMASK;
> @@ -291,13 +355,18 @@ static int dw_pcie_ep_get_msix(struct pci_epc *epc, u8 func_no)
>  	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
>  	u32 val, reg;
>  	unsigned int func_offset = 0;
> +	struct dw_pcie_ep_func *ep_func;
> +
> +	ep_func = dw_pcie_ep_get_func_from_ep(ep, func_no);
> +	if (!ep_func)
> +		return -EINVAL;
>  
> -	if (!ep->msix_cap)
> +	if (!ep_func->msix_cap)
>  		return -EINVAL;
>  
>  	func_offset = dw_pcie_ep_func_select(ep, func_no);
>  
> -	reg = ep->msix_cap + func_offset + PCI_MSIX_FLAGS;
> +	reg = ep_func->msix_cap + func_offset + PCI_MSIX_FLAGS;
>  	val = dw_pcie_readw_dbi(pci, reg);
>  	if (!(val & PCI_MSIX_FLAGS_ENABLE))
>  		return -EINVAL;
> @@ -313,13 +382,18 @@ static int dw_pcie_ep_set_msix(struct pci_epc *epc, u8 func_no, u16 interrupts)
>  	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
>  	u32 val, reg;
>  	unsigned int func_offset = 0;
> +	struct dw_pcie_ep_func *ep_func;
>  
> -	if (!ep->msix_cap)
> +	ep_func = dw_pcie_ep_get_func_from_ep(ep, func_no);
> +	if (!ep_func)
> +		return -EINVAL;
> +
> +	if (!ep_func->msix_cap)
>  		return -EINVAL;
>  
>  	func_offset = dw_pcie_ep_func_select(ep, func_no);
>  
> -	reg = ep->msix_cap + func_offset + PCI_MSIX_FLAGS;
> +	reg = ep_func->msix_cap + func_offset + PCI_MSIX_FLAGS;
>  	val = dw_pcie_readw_dbi(pci, reg);
>  	val &= ~PCI_MSIX_FLAGS_QSIZE;
>  	val |= interrupts;
> @@ -404,6 +478,7 @@ int dw_pcie_ep_raise_msi_irq(struct dw_pcie_ep *ep, u8 func_no,
>  			     u8 interrupt_num)
>  {
>  	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
> +	struct dw_pcie_ep_func *ep_func;
>  	struct pci_epc *epc = ep->epc;
>  	unsigned int aligned_offset;
>  	unsigned int func_offset = 0;
> @@ -413,25 +488,29 @@ int dw_pcie_ep_raise_msi_irq(struct dw_pcie_ep *ep, u8 func_no,
>  	bool has_upper;
>  	int ret;
>  
> -	if (!ep->msi_cap)
> +	ep_func = dw_pcie_ep_get_func_from_ep(ep, func_no);
> +	if (!ep_func)
> +		return -EINVAL;
> +
> +	if (!ep_func->msi_cap)
>  		return -EINVAL;
>  
>  	func_offset = dw_pcie_ep_func_select(ep, func_no);
>  
>  	/* Raise MSI per the PCI Local Bus Specification Revision 3.0, 6.8.1. */
> -	reg = ep->msi_cap + func_offset + PCI_MSI_FLAGS;
> +	reg = ep_func->msi_cap + func_offset + PCI_MSI_FLAGS;
>  	msg_ctrl = dw_pcie_readw_dbi(pci, reg);
>  	has_upper = !!(msg_ctrl & PCI_MSI_FLAGS_64BIT);
> -	reg = ep->msi_cap + func_offset + PCI_MSI_ADDRESS_LO;
> +	reg = ep_func->msi_cap + func_offset + PCI_MSI_ADDRESS_LO;
>  	msg_addr_lower = dw_pcie_readl_dbi(pci, reg);
>  	if (has_upper) {
> -		reg = ep->msi_cap + func_offset + PCI_MSI_ADDRESS_HI;
> +		reg = ep_func->msi_cap + func_offset + PCI_MSI_ADDRESS_HI;
>  		msg_addr_upper = dw_pcie_readl_dbi(pci, reg);
> -		reg = ep->msi_cap + func_offset + PCI_MSI_DATA_64;
> +		reg = ep_func->msi_cap + func_offset + PCI_MSI_DATA_64;
>  		msg_data = dw_pcie_readw_dbi(pci, reg);
>  	} else {
>  		msg_addr_upper = 0;
> -		reg = ep->msi_cap + func_offset + PCI_MSI_DATA_32;
> +		reg = ep_func->msi_cap + func_offset + PCI_MSI_DATA_32;
>  		msg_data = dw_pcie_readw_dbi(pci, reg);
>  	}
>  	aligned_offset = msg_addr_lower & (epc->mem->page_size - 1);
> @@ -467,6 +546,7 @@ int dw_pcie_ep_raise_msix_irq(struct dw_pcie_ep *ep, u8 func_no,
>  			      u16 interrupt_num)
>  {
>  	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
> +	struct dw_pcie_ep_func *ep_func;
>  	struct pci_epc *epc = ep->epc;
>  	u16 tbl_offset, bir;
>  	unsigned int func_offset = 0;
> @@ -477,9 +557,16 @@ int dw_pcie_ep_raise_msix_irq(struct dw_pcie_ep *ep, u8 func_no,
>  	void __iomem *msix_tbl;
>  	int ret;
>  
> +	ep_func = dw_pcie_ep_get_func_from_ep(ep, func_no);
> +	if (!ep_func)
> +		return -EINVAL;
> +
> +	if (!ep_func->msix_cap)
> +		return -EINVAL;
> +
>  	func_offset = dw_pcie_ep_func_select(ep, func_no);
>  
> -	reg = ep->msix_cap + func_offset + PCI_MSIX_TABLE;
> +	reg = ep_func->msix_cap + func_offset + PCI_MSIX_TABLE;
>  	tbl_offset = dw_pcie_readl_dbi(pci, reg);
>  	bir = (tbl_offset & PCI_MSIX_TABLE_BIR);
>  	tbl_offset &= PCI_MSIX_TABLE_OFFSET;
> @@ -558,6 +645,7 @@ int dw_pcie_ep_init(struct dw_pcie_ep *ep)
>  	int i;
>  	int ret;
>  	u32 reg;
> +	u8 func_no;
>  	void *addr;
>  	unsigned int nbars;
>  	unsigned int offset;
> @@ -565,6 +653,9 @@ int dw_pcie_ep_init(struct dw_pcie_ep *ep)
>  	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
>  	struct device *dev = pci->dev;
>  	struct device_node *np = dev->of_node;
> +	struct dw_pcie_ep_func *ep_func;
> +
> +	INIT_LIST_HEAD(&ep->func_list);
>  
>  	if (!pci->dbi_base || !pci->dbi_base2) {
>  		dev_err(dev, "dbi_base/dbi_base2 is not populated\n");
> @@ -624,9 +715,19 @@ int dw_pcie_ep_init(struct dw_pcie_ep *ep)
>  	if (ret < 0)
>  		epc->max_functions = 1;
>  
> -	ep->msi_cap = dw_pcie_find_capability(pci, PCI_CAP_ID_MSI);
> +	for (func_no = 0; func_no < epc->max_functions; func_no++) {
> +		ep_func = devm_kzalloc(dev, sizeof(*ep_func), GFP_KERNEL);
> +		if (!ep_func)
> +			return -ENOMEM;
>  
> -	ep->msix_cap = dw_pcie_find_capability(pci, PCI_CAP_ID_MSIX);
> +		ep_func->func_no = func_no;
> +		ep_func->msi_cap = dw_pcie_ep_find_capability(ep, func_no,
> +							      PCI_CAP_ID_MSI);
> +		ep_func->msix_cap = dw_pcie_ep_find_capability(ep, func_no,
> +							       PCI_CAP_ID_MSIX);
> +
> +		list_add_tail(&ep_func->list, &ep->func_list);
> +	}

Whilst your patch addresses the issue of giving each function the ability to
have differing capabilities - I feel that this solution doesn't go deep enough.

In my view the root issue here is that 'struct dw_pcie_ep' represents both a
EP controller and a *single* EP function. I think that there should be a
representation for an EP controller and a representation for a EP function
(i.e. some separation). Thus allowing one EP controller to have many EP
functions. This isn't too dissimilar to host bridges and their functions.
Others here may have different views.

It may be unlikely now, but EP functions belonging to the same bit of IP may
have differing functionality - your approach addresses that for MSI/MSI
capabilities, but what about other differences?

(It would be really nice as well if an EP controller could provide config
read/write ops such that existing functions in the core such as
__pci_find_next_capability could be reused - instead of copying them
like dw_pcie_ep_find_capability. However I don't think this is feasible.)

Thanks,

Andrew Murray

>  
>  	if (ep->ops->ep_init)
>  		ep->ops->ep_init(ep);
> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> index 56789be..a57743c 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.h
> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> @@ -221,8 +221,16 @@ struct dw_pcie_ep_ops {
>  	unsigned int (*func_conf_select)(struct dw_pcie_ep *ep, u8 func_no);
>  };
>  
> +struct dw_pcie_ep_func {
> +	struct list_head	list;
> +	u8			func_no;
> +	u8			msi_cap;	/* MSI capability offset */
> +	u8			msix_cap;	/* MSI-X capability offset */
> +};
> +
>  struct dw_pcie_ep {
>  	struct pci_epc		*epc;
> +	struct list_head	func_list;
>  	const struct dw_pcie_ep_ops *ops;
>  	phys_addr_t		phys_base;
>  	size_t			addr_size;
> @@ -235,8 +243,6 @@ struct dw_pcie_ep {
>  	u32			num_ob_windows;
>  	void __iomem		*msi_mem;
>  	phys_addr_t		msi_mem_phys;
> -	u8			msi_cap;	/* MSI capability offset */
> -	u8			msix_cap;	/* MSI-X capability offset */
>  };
>  
>  struct dw_pcie_ops {
> @@ -425,6 +431,8 @@ int dw_pcie_ep_raise_msix_irq(struct dw_pcie_ep *ep, u8 func_no,
>  int dw_pcie_ep_raise_msix_irq_doorbell(struct dw_pcie_ep *ep, u8 func_no,
>  				       u16 interrupt_num);
>  void dw_pcie_ep_reset_bar(struct dw_pcie *pci, enum pci_barno bar);
> +struct dw_pcie_ep_func *
> +dw_pcie_ep_get_func_from_ep(struct dw_pcie_ep *ep, u8 func_no);
>  #else
>  static inline void dw_pcie_ep_linkup(struct dw_pcie_ep *ep)
>  {
> @@ -466,5 +474,11 @@ static inline int dw_pcie_ep_raise_msix_irq_doorbell(struct dw_pcie_ep *ep,
>  static inline void dw_pcie_ep_reset_bar(struct dw_pcie *pci, enum pci_barno bar)
>  {
>  }
> +
> +struct dw_pcie_ep_func *
> +dw_pcie_ep_get_func_from_ep(struct dw_pcie_ep *ep, u8 func_no)
> +{
> +	return NULL;
> +}
>  #endif
>  #endif /* _PCIE_DESIGNWARE_H */
> -- 
> 2.9.5
> 

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