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Message-ID: <20240308054152.GD3789@thinkpad>
Date: Fri, 8 Mar 2024 11:11:52 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Niklas Cassel <cassel@...nel.org>
Cc: Jingoo Han <jingoohan1@...il.com>,
Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
Lorenzo Pieralisi <lpieralisi@...nel.org>,
Krzysztof Wilczyński <kw@...ux.com>,
Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
Marek Vasut <marek.vasut+renesas@...il.com>,
Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
Thierry Reding <thierry.reding@...il.com>,
Jonathan Hunter <jonathanh@...dia.com>,
Kishon Vijay Abraham I <kishon@...com>,
Vidya Sagar <vidyas@...dia.com>,
Vignesh Raghavendra <vigneshr@...com>,
Richard Zhu <hongxing.zhu@....com>,
Lucas Stach <l.stach@...gutronix.de>,
Shawn Guo <shawnguo@...nel.org>,
Sascha Hauer <s.hauer@...gutronix.de>,
Pengutronix Kernel Team <kernel@...gutronix.de>,
Fabio Estevam <festevam@...il.com>,
NXP Linux Team <linux-imx@....com>,
Minghuan Lian <minghuan.Lian@....com>,
Mingkai Hu <mingkai.hu@....com>, Roy Zang <roy.zang@....com>,
Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>,
Masami Hiramatsu <mhiramat@...nel.org>,
Kishon Vijay Abraham I <kishon@...nel.org>,
Jesper Nilsson <jesper.nilsson@...s.com>,
Srikanth Thokala <srikanth.thokala@...el.com>,
linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-renesas-soc@...r.kernel.org, linux-arm-msm@...r.kernel.org,
linux-tegra@...r.kernel.org, linux-omap@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linuxppc-dev@...ts.ozlabs.org,
linux-arm-kernel@...s.com
Subject: Re: [PATCH v9 08/10] PCI: dwc: ep: Add a generic
dw_pcie_ep_linkdown() API to handle LINK_DOWN event
On Thu, Mar 07, 2024 at 10:43:19PM +0100, Niklas Cassel wrote:
> On Mon, Mar 04, 2024 at 02:52:20PM +0530, Manivannan Sadhasivam wrote:
> > The PCIe link can go to LINK_DOWN state in one of the following scenarios:
> >
> > 1. Fundamental (PERST#)/hot/warm reset
> > 2. Link transition from L2/L3 to L0
> >
> > In those cases, LINK_DOWN causes some non-sticky DWC registers to loose the
> > state (like REBAR, PTM_CAP 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.
> >
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > ---
> > drivers/pci/controller/dwc/pcie-designware-ep.c | 111 ++++++++++++++----------
> > drivers/pci/controller/dwc/pcie-designware.h | 5 ++
> > 2 files changed, 72 insertions(+), 44 deletions(-)
> >
> > diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
> > index 278bdc9b2269..fed4c2936c78 100644
> > --- a/drivers/pci/controller/dwc/pcie-designware-ep.c
> > +++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
> > @@ -14,14 +14,6 @@
> > #include <linux/pci-epc.h>
> > #include <linux/pci-epf.h>
> >
> > -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);
> > -
> > void dw_pcie_ep_init_notify(struct dw_pcie_ep *ep)
> > {
> > struct pci_epc *epc = ep->epc;
> > @@ -603,19 +595,56 @@ 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, ptm_cap_base;
> > + unsigned int nbars;
> > + u32 reg, i;
> > +
> > + 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);
>
> If you look at PCI_REBAR_CAP, you will see that it is sticky,
> but you have to actually read the databook to see that:
>
> "The RESBAR_CTRL_REG_BAR_SIZE field is automatically updated
> when you write to RESBAR_CAP_REG_0_REG through the DBI."
>
> So the reason why we need to write this register, even though
> it is sticky, is to update the RESBAR_CTRL_REG_BAR_SIZE register,
> which is not sticky :)
>
> (Perhaps we should add that as a comment?)
>
Yeah, makes sense.
>
> > + }
> > +
> > + /*
> > + * PTM responder capability can be disabled only after disabling
> > + * PTM root capability.
> > + */
> > + if (ptm_cap_base) {
> > + dw_pcie_dbi_ro_wr_en(pci);
> > + reg = dw_pcie_readl_dbi(pci, ptm_cap_base + PCI_PTM_CAP);
> > + reg &= ~PCI_PTM_CAP_ROOT;
> > + dw_pcie_writel_dbi(pci, ptm_cap_base + PCI_PTM_CAP, reg);
> > +
> > + reg = dw_pcie_readl_dbi(pci, ptm_cap_base + PCI_PTM_CAP);
> > + reg &= ~(PCI_PTM_CAP_RES | PCI_PTM_GRANULARITY_MASK);
> > + dw_pcie_writel_dbi(pci, ptm_cap_base + PCI_PTM_CAP, reg);
> > + dw_pcie_dbi_ro_wr_dis(pci);
>
> From looking at the databook:
> PCI_PTM_CAP_ROOT:
> Note: This register field is sticky.
>
> PCI_PTM_CAP_RES:
> Note: This register field is sticky.
>
> PCI_PTM_GRANULARITY_MASK:
> Dbi: if (DBI_RO_WR_EN == 1) then R/W(sticky) else
> R(sticky)
>
> So all these register fields appear to be sticky to me.
> So I would assume that the PTM related writes could be
> done in dw_pcie_ep_init_registers().
>
Sorry, I didn't cross check the registers w/ databook as I was under the
assumption that all PTM registers are non-sticky. Will move them.
- Mani
>
> > + }
> > +
> > + dw_pcie_setup(pci);
> > + dw_pcie_dbi_ro_wr_dis(pci);
> > +}
> > +
> > int dw_pcie_ep_init_registers(struct dw_pcie_ep *ep)
> > {
> > struct dw_pcie *pci = to_dw_pcie_from_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;
> > 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;
> > @@ -678,38 +707,7 @@ 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.
> > - */
> > - if (ptm_cap_base) {
> > - dw_pcie_dbi_ro_wr_en(pci);
> > - reg = dw_pcie_readl_dbi(pci, ptm_cap_base + PCI_PTM_CAP);
> > - reg &= ~PCI_PTM_CAP_ROOT;
> > - dw_pcie_writel_dbi(pci, ptm_cap_base + PCI_PTM_CAP, reg);
> > -
> > - reg = dw_pcie_readl_dbi(pci, ptm_cap_base + PCI_PTM_CAP);
> > - reg &= ~(PCI_PTM_CAP_RES | PCI_PTM_GRANULARITY_MASK);
> > - dw_pcie_writel_dbi(pci, ptm_cap_base + PCI_PTM_CAP, reg);
> > - dw_pcie_dbi_ro_wr_dis(pci);
> > - }
> > -
> > - dw_pcie_setup(pci);
> > - dw_pcie_dbi_ro_wr_dis(pci);
> > + dw_pcie_ep_init_non_sticky_registers(pci);
> >
> > return 0;
> >
> > @@ -720,6 +718,31 @@ int dw_pcie_ep_init_registers(struct dw_pcie_ep *ep)
> > }
> > EXPORT_SYMBOL_GPL(dw_pcie_ep_init_registers);
> >
> > +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);
> > +
> > +void dw_pcie_ep_linkdown(struct dw_pcie_ep *ep)
> > +{
> > + struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
> > + struct pci_epc *epc = ep->epc;
> > +
> > + /*
> > + * Initialize the non-sticky DWC registers as they would've reset post
> > + * LINK_DOWN. This is specifically needed for drivers not supporting
> > + * PERST# as they have no way to reinitialize the registers before the
> > + * link comes back again.
> > + */
> > + dw_pcie_ep_init_non_sticky_registers(pci);
> > +
> > + pci_epc_linkdown(epc);
> > +}
> > +EXPORT_SYMBOL_GPL(dw_pcie_ep_linkdown);
> > +
> > int dw_pcie_ep_init(struct dw_pcie_ep *ep)
> > {
> > int ret;
> > diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> > index f8e5431a207b..152969545b0a 100644
> > --- a/drivers/pci/controller/dwc/pcie-designware.h
> > +++ b/drivers/pci/controller/dwc/pcie-designware.h
> > @@ -668,6 +668,7 @@ static inline void __iomem *dw_pcie_own_conf_map_bus(struct pci_bus *bus,
> >
> > #ifdef CONFIG_PCIE_DW_EP
> > void dw_pcie_ep_linkup(struct dw_pcie_ep *ep);
> > +void dw_pcie_ep_linkdown(struct dw_pcie_ep *ep);
> > int dw_pcie_ep_init(struct dw_pcie_ep *ep);
> > int dw_pcie_ep_init_registers(struct dw_pcie_ep *ep);
> > void dw_pcie_ep_init_notify(struct dw_pcie_ep *ep);
> > @@ -688,6 +689,10 @@ static inline void dw_pcie_ep_linkup(struct dw_pcie_ep *ep)
> > {
> > }
> >
> > +static inline void dw_pcie_ep_linkdown(struct dw_pcie_ep *ep)
> > +{
> > +}
> > +
> > static inline int dw_pcie_ep_init(struct dw_pcie_ep *ep)
> > {
> > return 0;
> >
> > --
> > 2.25.1
> >
--
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