Re: [PATCH 07/11] PCI: dwc: ep: Add a generic dw_pcie_ep_linkdown() API to handle Link Down event

[Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>]

On Wed, Mar 27, 2024 at 07:06:30PM +0100, Niklas Cassel wrote:
> Hello Mani,
> 
> On Thu, Mar 14, 2024 at 08:53:46PM +0530, Manivannan Sadhasivam wrote:
> > As per the PCIe base spec r5.0, section 5.2, Link Down event can happen
> > under any of the following circumstances:
> > 
> > 1. Fundamental/Hot reset
> > 2. Link disable transmission by upstream component
> > 3. Moving from L2/L3 to L0
> > 
> > In those cases, Link Down causes some non-sticky DWC registers to loose the
> > state (like REBAR, etc...). So the drivers need to reinitialize them to
> > function properly once the link comes back again.
> > 
> > This is not a problem for drivers supporting PERST# IRQ, since they can
> > reinitialize the registers in the PERST# IRQ callback. But for the drivers
> > not supporting PERST#, there is no way they can reinitialize the registers
> > other than relying on Link Down IRQ received when the link goes down. So
> > let's add a DWC generic API dw_pcie_ep_linkdown() that reinitializes the
> > non-sticky registers and also notifies the EPF drivers about link going
> > down.
> > 
> > This API can also be used by the drivers supporting PERST# to handle the
> > scenario (2) mentioned above.
> > 
> > NOTE: For the sake of code organization, move the dw_pcie_ep_linkup()
> > definition just above dw_pcie_ep_linkdown().
> > 
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> > ---
> >  drivers/pci/controller/dwc/pcie-designware-ep.c | 93 ++++++++++++++++---------
> >  drivers/pci/controller/dwc/pcie-designware.h    |  5 ++
> >  2 files changed, 67 insertions(+), 31 deletions(-)
> > 
> > diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
> > index 3893a8c1a11c..5451057ca74b 100644
> > --- a/drivers/pci/controller/dwc/pcie-designware-ep.c
> > +++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
> > @@ -14,18 +14,6 @@
> >  #include <linux/pci-epc.h>
> >  #include <linux/pci-epf.h>
> >  
> > -/**
> > - * dw_pcie_ep_linkup - Notify EPF drivers about link up event
> > - * @ep: DWC EP device
> > - */
> > -void dw_pcie_ep_linkup(struct dw_pcie_ep *ep)
> > -{
> > -	struct pci_epc *epc = ep->epc;
> > -
> > -	pci_epc_linkup(epc);
> > -}
> > -EXPORT_SYMBOL_GPL(dw_pcie_ep_linkup);
> > -
> >  /**
> >   * dw_pcie_ep_init_notify - Notify EPF drivers about EPC initialization
> >   *			    complete
> > @@ -672,6 +660,29 @@ static unsigned int dw_pcie_ep_find_ext_capability(struct dw_pcie *pci, int cap)
> >  	return 0;
> >  }
> >  
> > +static void dw_pcie_ep_init_non_sticky_registers(struct dw_pcie *pci)
> > +{
> > +	unsigned int offset;
> > +	unsigned int nbars;
> > +	u32 reg, i;
> > +
> > +	offset = dw_pcie_ep_find_ext_capability(pci, PCI_EXT_CAP_ID_REBAR);
> > +
> > +	dw_pcie_dbi_ro_wr_en(pci);
> > +
> > +	if (offset) {
> > +		reg = dw_pcie_readl_dbi(pci, offset + PCI_REBAR_CTRL);
> > +		nbars = (reg & PCI_REBAR_CTRL_NBAR_MASK) >>
> > +			PCI_REBAR_CTRL_NBAR_SHIFT;
> > +
> > +		for (i = 0; i < nbars; i++, offset += PCI_REBAR_CTRL)
> > +			dw_pcie_writel_dbi(pci, offset + PCI_REBAR_CAP, 0x0);
> > +	}
> > +
> > +	dw_pcie_setup(pci);
> > +	dw_pcie_dbi_ro_wr_dis(pci);
> > +}
> > +
> >  /**
> >   * dw_pcie_ep_init_registers - Initialize DWC EP specific registers
> >   * @ep: DWC EP device
> > @@ -686,13 +697,11 @@ int dw_pcie_ep_init_registers(struct dw_pcie_ep *ep)
> >  	struct dw_pcie_ep_func *ep_func;
> >  	struct device *dev = pci->dev;
> >  	struct pci_epc *epc = ep->epc;
> > -	unsigned int offset, ptm_cap_base;
> > -	unsigned int nbars;
> > +	u32 ptm_cap_base, reg;
> >  	u8 hdr_type;
> >  	u8 func_no;
> > -	int i, ret;
> >  	void *addr;
> > -	u32 reg;
> > +	int ret;
> >  
> >  	hdr_type = dw_pcie_readb_dbi(pci, PCI_HEADER_TYPE) &
> >  		   PCI_HEADER_TYPE_MASK;
> > @@ -755,20 +764,8 @@ int dw_pcie_ep_init_registers(struct dw_pcie_ep *ep)
> >  	if (ep->ops->init)
> >  		ep->ops->init(ep);
> >  
> > -	offset = dw_pcie_ep_find_ext_capability(pci, PCI_EXT_CAP_ID_REBAR);
> >  	ptm_cap_base = dw_pcie_ep_find_ext_capability(pci, PCI_EXT_CAP_ID_PTM);
> >  
> > -	dw_pcie_dbi_ro_wr_en(pci);
> > -
> > -	if (offset) {
> > -		reg = dw_pcie_readl_dbi(pci, offset + PCI_REBAR_CTRL);
> > -		nbars = (reg & PCI_REBAR_CTRL_NBAR_MASK) >>
> > -			PCI_REBAR_CTRL_NBAR_SHIFT;
> > -
> > -		for (i = 0; i < nbars; i++, offset += PCI_REBAR_CTRL)
> > -			dw_pcie_writel_dbi(pci, offset + PCI_REBAR_CAP, 0x0);
> > -	}
> > -
> >  	/*
> >  	 * PTM responder capability can be disabled only after disabling
> >  	 * PTM root capability.
> > @@ -785,9 +782,6 @@ int dw_pcie_ep_init_registers(struct dw_pcie_ep *ep)
> >  		dw_pcie_dbi_ro_wr_dis(pci);
> >  	}
> >  
> > -	dw_pcie_setup(pci);
> > -	dw_pcie_dbi_ro_wr_dis(pci);
> > -
> 
> Your previous series had:
> 
> -       dw_pcie_setup(pci);
> -       dw_pcie_dbi_ro_wr_dis(pci);
> +       dw_pcie_ep_init_non_sticky_registers(pci);
> 
> Here.
> I tested this series, but it did not work for me (the Resizable BARs did
> not get resized) since you removed the call to
> dw_pcie_ep_init_non_sticky_registers().
> 
> By readding the call to dw_pcie_ep_init_non_sticky_registers(),
> the BARs get Resized again.
> 
> 

Ah, looks like rebase has gone bad. Will fix it in v2.

> BTW do you have a git branch with both your series somewhere?
> (Possibly even rebased on
> https://lore.kernel.org/linux-pci/20240320113157.322695-1-cassel@kernel.org/T/#t
> like you suggested in your other mail.)
> 

There it is: https://git.codelinaro.org/manivannan.sadhasivam/linux/-/tree/b4/pci-epf-rework

- Mani

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