Re: [PATCH v4 5/5] PCI: dwc: Add common send PME_Turn_Off message method

Manivannan Sadhasivam
2024-03-19T04:25:26Z

On Mon, Feb 26, 2024 at 05:43:29PM -0500, Frank Li wrote:
> On Tue, Feb 27, 2024 at 12:52:45AM +0300, Serge Semin wrote:
> > On Tue, Feb 13, 2024 at 04:50:26PM -0500, Frank Li wrote:
> > > Reserve space at end of first IORESOURCE_MEM window as message TLP MMIO
> > > window. This space's size is 'region_align'.
> > >
> > > Set outbound ATU map memory write to send PCI message. So one MMIO write
> > > can trigger a PCI message, such as PME_Turn_Off.
> > >
> > > Add common dwc_pme_turn_off() function.
> > >
> > > Call dwc_pme_turn_off() to send out PME_Turn_Off message in general
> > > dw_pcie_suspend_noirq() if there are not platform callback pme_turn_off()
> > > exist.
> > >
> > > Signed-off-by: Frank Li <Frank.Li@nxp.com>
> > > ---
> > > drivers/pci/controller/dwc/pcie-designware-host.c | 93 ++++++++++++++++++++++-
> > > drivers/pci/controller/dwc/pcie-designware.h | 2 +
> > > 2 files changed, 91 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> > > index 267687ab33cbc..5e83756492462 100644
> > > --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> > > +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> > > @@ -393,6 +393,31 @@ static int dw_pcie_msi_host_init(struct dw_pcie_rp *pp)
> > > return 0;
> > > }
> > >
> > > +static void dw_pcie_host_request_msg_tlp_res(struct dw_pcie_rp *pp)
> > > +{
> > > + struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> > > + struct resource_entry *win;
> > > + struct resource *res;
> > > +
> > > + win = resource_list_first_type(&pp->bridge->windows, IORESOURCE_MEM);
> > > + if (win) {
> > > + res = devm_kzalloc(pci->dev, sizeof(*res), GFP_KERNEL);
> > > + if (!res)
> > > + return;
> > > +
> > > + /* Reserve last region_align block as message TLP space */
> > > + res->start = win->res->end - pci->region_align + 1;
> > > + res->end = win->res->end;
> > > + res->name = "msg";
> > > + res->flags = win->res->flags | IORESOURCE_BUSY;
> > > +
> > > + if (!request_resource(win->res, res))
> > > + pp->msg_res = res;
> > > + else
> > > + devm_kfree(pci->dev, res);
> > > + }
> > > +}
> > > +
> > > int dw_pcie_host_init(struct dw_pcie_rp *pp)
> > > {
> > > struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> > > @@ -479,6 +504,9 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp)
> > >
> > > dw_pcie_iatu_detect(pci);
> > >
> >
> > > + /* Need call after dw_pcie_iatu_detect() before dw_pcie_setup_rc() */
> > > + dw_pcie_host_request_msg_tlp_res(pp);
> >
> > This may cause regressions for instance if the outbound memory window
> > is small and is fully dedicated for some device like VGA/GPU/etc.
>
> There are host memory map windows, which are quite big. It will be too
> small if only because one page size windows less.
>
> Look like it is impossible to dedicated to one device, all pcie devices
> (VGA/GPU) should go through standard pcie probe flow, the bar will be
> allocated from bridge windows space.
>

No, Sergey's concern is still valid. You are allocating the memory for TLPs at
the end of the existing MEM range. But there is a chance that it could cause
memory hungry devices like GPU to run out of memory in an existing setup.

That being said, I also do not want to hold off merging this series. So let's
make this region opt-in for drivers making use of this feature. This way, if we
migrate to a dedicated 'ranges' region in the future, we can remove the
conditional check and base the check on the existence of the new region.

- Mani

> >
> > Why not to use a new ranges-based mapping as we discussed earlier:
> > https://lore.kernel.org/linux-pci/20240214061412.GB4618@thinkpad/
> > ?
>
> If driver can auto alloc from known range, why need static defined in dts
> files.
>
> static alloc can't resolve small outbound memory windows problem. It may
> disable this feature.
>
> >
> > I know it might be troublesome but still it would be much better
> > and more portable across various platforms.
> >
> > Bjorn, Lorenzo, Krzysztofm Rob could you please follow the link above
> > and give your opinion about the solution suggested there?
> >
> > -Serge(y)
> >
> > > +
> > > ret = dw_pcie_edma_detect(pci);
> > > if (ret)
> > > goto err_free_msi;
> > > @@ -536,6 +564,11 @@ void dw_pcie_host_deinit(struct dw_pcie_rp *pp)
> > >
> > > dw_pcie_edma_remove(pci);
> > >
> > > + if (pp->msg_res) {
> > > + release_resource(pp->msg_res);
> > > + devm_kfree(pci->dev, pp->msg_res);
> > > + }
> > > +
> > > if (pp->has_msi_ctrl)
> > > dw_pcie_free_msi(pp);
> > >
> > > @@ -697,6 +730,10 @@ static int dw_pcie_iatu_setup(struct dw_pcie_rp *pp)
> > > atu.pci_addr = entry->res->start - entry->offset;
> > > atu.size = resource_size(entry->res);
> > >
> > > + /* MSG TLB window resource reserve at one of end of IORESOURCE_MEM resource */
> > > + if (pp->msg_res && pp->msg_res->parent == entry->res)
> > > + atu.size -= resource_size(pp->msg_res);
> > > +
> > > ret = dw_pcie_prog_outbound_atu(pci, &atu);
> > > if (ret) {
> > > dev_err(pci->dev, "Failed to set MEM range %pr\n",
> > > @@ -728,6 +765,8 @@ static int dw_pcie_iatu_setup(struct dw_pcie_rp *pp)
> > > dev_warn(pci->dev, "Ranges exceed outbound iATU size (%d)\n",
> > > pci->num_ob_windows);
> > >
> > > + pp->msg_atu_index = i;
> > > +
> > > i = 0;
> > > resource_list_for_each_entry(entry, &pp->bridge->dma_ranges) {
> > > if (resource_type(entry->res) != IORESOURCE_MEM)
> > > @@ -833,11 +872,54 @@ int dw_pcie_setup_rc(struct dw_pcie_rp *pp)
> > > }
> > > EXPORT_SYMBOL_GPL(dw_pcie_setup_rc);
> > >
> > > +/* Using message outbound ATU to send out PME_Turn_Off message for dwc PCIe controller */
> > > +static int dw_pcie_pme_turn_off(struct dw_pcie *pci)
> > > +{
> > > + struct dw_pcie_ob_atu_cfg atu = { 0 };
> > > + void __iomem *m;
> > > + int ret;
> > > +
> > > + if (pci->num_ob_windows <= pci->pp.msg_atu_index)
> > > + return -EINVAL;
> > > +
> > > + if (!pci->pp.msg_res)
> > > + return -EINVAL;
> > > +
> > > + atu.code = PCIE_MSG_CODE_PME_TURN_OFF;
> > > + atu.routing = PCIE_MSG_TYPE_R_BC;
> > > + atu.type = PCIE_ATU_TYPE_MSG;
> > > + atu.size = resource_size(pci->pp.msg_res);
> > > + atu.index = pci->pp.msg_atu_index;
> > > +
> > > + if (!atu.size) {
> > > + dev_dbg(pci->dev,
> > > + "atu memory map windows is zero, please check 'msg' reg in dts\n");
> > > + return -ENOMEM;
> > > + }
> > > +
> > > + atu.cpu_addr = pci->pp.msg_res->start;
> > > +
> > > + ret = dw_pcie_prog_outbound_atu(pci, &atu);
> > > + if (ret)
> > > + return ret;
> > > +
> > > + m = ioremap(atu.cpu_addr, pci->region_align);
> > > + if (!m)
> > > + return -ENOMEM;
> > > +
> > > + /* A dummy write is converted to a Msg TLP */
> > > + writel(0, m);
> > > +
> > > + iounmap(m);
> > > +
> > > + return 0;
> > > +}
> > > +
> > > int dw_pcie_suspend_noirq(struct dw_pcie *pci)
> > > {
> > > u8 offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
> > > u32 val;
> > > - int ret;
> > > + int ret = 0;
> > >
> > > /*
> > > * If L1SS is supported, then do not put the link into L2 as some
> > > @@ -849,10 +931,13 @@ int dw_pcie_suspend_noirq(struct dw_pcie *pci)
> > > if (dw_pcie_get_ltssm(pci) <= DW_PCIE_LTSSM_DETECT_ACT)
> > > return 0;
> > >
> > > - if (!pci->pp.ops->pme_turn_off)
> > > - return 0;
> > > + if (pci->pp.ops->pme_turn_off)
> > > + pci->pp.ops->pme_turn_off(&pci->pp);
> > > + else
> > > + ret = dw_pcie_pme_turn_off(pci);
> > >
> > > - pci->pp.ops->pme_turn_off(&pci->pp);
> > > + if (ret)
> > > + return ret;
> > >
> > > ret = read_poll_timeout(dw_pcie_get_ltssm, val, val == DW_PCIE_LTSSM_L2_IDLE,
> > > PCIE_PME_TO_L2_TIMEOUT_US/10,
> > > diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> > > index 703b50bc5e0f1..9e6076aa4c850 100644
> > > --- a/drivers/pci/controller/dwc/pcie-designware.h
> > > +++ b/drivers/pci/controller/dwc/pcie-designware.h
> > > @@ -341,6 +341,8 @@ struct dw_pcie_rp {
> > > struct pci_host_bridge *bridge;
> > > raw_spinlock_t lock;
> > > DECLARE_BITMAP(msi_irq_in_use, MAX_MSI_IRQS);
> > > + int msg_atu_index;
> > > + struct resource *msg_res;
> > > };
> > >
> > > struct dw_pcie_ep_ops {
> > >
> > > --
> > > 2.34.1
> > >
> > >

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