Re: [PATCH] PCI: dwc: Move allocate and map page for msi out of dw_pcie_msi_init()

[Jisheng Zhang]

Hi Rob,

On Wed, 23 Sep 2020 10:41:45 -0600 Rob Herring wrote:

> 
> On Wed, Sep 23, 2020 at 12:27 AM Jisheng Zhang
> <Jisheng.Zhang@xxxxxxxxxxxxx> wrote:
> >
> > Currently, dw_pcie_msi_init() allocates and maps page for msi, then
> > program the PCIE_MSI_ADDR_LO and PCIE_MSI_ADDR_HI. The Root Complex
> > may lose power during suspend-to-RAM, so when we resume, we want to
> > redo the latter but not the former. If designware based driver (for
> > example, pcie-tegra194.c) calls dw_pcie_msi_init() in resume path, the
> > previous msi page will be leaked.  
> 
> It's worse than this. I think there's also error paths too leaking the

I think you mean the leaking in pcie-tegra194.c's error path. Synaptics
SoC pcie driver(not mainlined) needs to call dw_pcie_msi_init() in resume
path, pcie-tegra194.c shares the same problem, so I mentioned it in the commit
msg, but the patch isn't targeting to fix all the leaking issues in
pcie-tegra194.c. This patch at least fix one of the issue. 

> page. Also, there's never a dma_unmap_page call which should happen
> before freeing.

Thanks for pointing it out. I will add it in v2

> 
> > Move the allocate and map msi page from dw_pcie_msi_init() to
> > dw_pcie_host_init() to fix this problem.
> >
> > Fixes: 56e15a238d92 ("PCI: tegra: Add Tegra194 PCIe support")
> > Signed-off-by: Jisheng Zhang <Jisheng.Zhang@xxxxxxxxxxxxx>
> > ---
> >  drivers/pci/controller/dwc/pci-dra7xx.c       | 18 ++++++++++++-
> >  .../pci/controller/dwc/pcie-designware-host.c | 27 +++++++++----------
> >  2 files changed, 30 insertions(+), 15 deletions(-)
> >
> > diff --git a/drivers/pci/controller/dwc/pci-dra7xx.c b/drivers/pci/controller/dwc/pci-dra7xx.c
> > index dc387724cf08..4301cf844a4c 100644
> > --- a/drivers/pci/controller/dwc/pci-dra7xx.c
> > +++ b/drivers/pci/controller/dwc/pci-dra7xx.c
> > @@ -490,7 +490,9 @@ static struct irq_chip dra7xx_pci_msi_bottom_irq_chip = {
> >  static int dra7xx_pcie_msi_host_init(struct pcie_port *pp)
> >  {
> >         struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> > +       struct device *dev = pci->dev;
> >         u32 ctrl, num_ctrls;
> > +       int ret;
> >
> >         pp->msi_irq_chip = &dra7xx_pci_msi_bottom_irq_chip;
> >
> > @@ -506,7 +508,21 @@ static int dra7xx_pcie_msi_host_init(struct pcie_port *pp)
> >                                     ~0);
> >         }
> >
> > -       return dw_pcie_allocate_domains(pp);
> > +       ret = dw_pcie_allocate_domains(pp);
> > +       if (ret)
> > +               return ret;
> > +
> > +       pp->msi_page = alloc_page(GFP_KERNEL);
> > +       pp->msi_data = dma_map_page(dev, pp->msi_page, 0, PAGE_SIZE,
> > +                                   DMA_FROM_DEVICE);
> > +       ret = dma_mapping_error(dev, pp->msi_data);
> > +       if (ret) {
> > +               dev_err(dev, "Failed to map MSI data\n");
> > +               __free_page(pp->msi_page);
> > +               pp->msi_page = NULL;
> > +               dw_pcie_free_msi(pp);
> > +       }  
> 
> I don't like having 2 copies of the same thing. Also, doesn't keystone
> need this too?

what about introduce dw_pcie_msi_alloc() to do this?

IIUC, keystone doesn't need this.

> 
> The other thing is .msi_host_init() is abused by having an empty
> function to disable MSI support. We should have a flag instead to
> enable/disable MSI support and then we can key off of that in the
> common code.

FWICT, the .msi_host_init() is to init soc's own msi support rather
than init the DWC's integrated MSI module. So the usage is correct.

> 
> > +       return ret;
> >  }
> >
> >  static const struct dw_pcie_host_ops dra7xx_pcie_host_ops = {
> > diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> > index 9dafecba347f..c23ba64f64fe 100644
> > --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> > +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> > @@ -294,20 +294,7 @@ void dw_pcie_free_msi(struct pcie_port *pp)
> >
> >  void dw_pcie_msi_init(struct pcie_port *pp)  
> 
> Might be good to rename this function with exactly what it does.
> There's too many 'init' and 'setup' functions...

If we move the msi page allocation out of dw_pcie_msi_init(), then
it only initializes the integrated MSI.

Thanks

> 
> >  {
> > -       struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> > -       struct device *dev = pci->dev;
> > -       u64 msi_target;
> > -
> > -       pp->msi_page = alloc_page(GFP_KERNEL);
> > -       pp->msi_data = dma_map_page(dev, pp->msi_page, 0, PAGE_SIZE,
> > -                                   DMA_FROM_DEVICE);
> > -       if (dma_mapping_error(dev, pp->msi_data)) {
> > -               dev_err(dev, "Failed to map MSI data\n");
> > -               __free_page(pp->msi_page);
> > -               pp->msi_page = NULL;
> > -               return;
> > -       }
> > -       msi_target = (u64)pp->msi_data;
> > +       u64 msi_target = (u64)pp->msi_data;
> >
> >         /* Program the msi_data */
> >         dw_pcie_wr_own_conf(pp, PCIE_MSI_ADDR_LO, 4,
> > @@ -440,6 +427,18 @@ int dw_pcie_host_init(struct pcie_port *pp)
> >                                 irq_set_chained_handler_and_data(pp->msi_irq,
> >                                                             dw_chained_msi_isr,
> >                                                             pp);
> > +
> > +                       pp->msi_page = alloc_page(GFP_KERNEL);
> > +                       pp->msi_data = dma_map_page(pci->dev, pp->msi_page,
> > +                                                   0, PAGE_SIZE,
> > +                                                   DMA_FROM_DEVICE);
> > +                       ret = dma_mapping_error(pci->dev, pp->msi_data);
> > +                       if (ret) {
> > +                               dev_err(pci->dev, "Failed to map MSI data\n");
> > +                               __free_page(pp->msi_page);
> > +                               pp->msi_page = NULL;
> > +                               goto err_free_msi;
> > +                       }
> >                 } else {
> >                         ret = pp->ops->msi_host_init(pp);
> >                         if (ret < 0)
> > --
> > 2.28.0
> >