linux-kernel - Re: [PATCH V4 05/16] PCI: dwc: Move config space capability search API

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Date:   Wed, 24 Apr 2019 13:42:43 +1000
From:   Oliver <oohall@...il.com>
To:     Vidya Sagar <vidyas@...dia.com>
Cc:     Bjorn Helgaas <helgaas@...nel.org>, lorenzo.pieralisi@....com,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>, thierry.reding@...il.com,
        jonathanh@...dia.com, kishon@...com,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>, jingoohan1@...il.com,
        gustavo.pimentel@...opsys.com, mperttunen@...dia.com,
        linux-pci@...r.kernel.org,
        Device Tree <devicetree@...r.kernel.org>,
        linux-tegra@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-kernel@...ts.infradead.org, kthota@...dia.com,
        mmaddireddy@...dia.com, sagar.tv@...il.com
Subject: Re: [PATCH V4 05/16] PCI: dwc: Move config space capability search API

On Wed, Apr 24, 2019 at 1:12 PM Vidya Sagar <vidyas@...dia.com> wrote:
>
> On 4/24/2019 2:02 AM, Bjorn Helgaas wrote:
> > On Tue, Apr 23, 2019 at 01:57:19PM +0530, Vidya Sagar wrote:
> >> Move PCIe config space capability search API to common DesignWare file
> >> as this can be used by both host and ep mode codes.
> >>
> >> Signed-off-by: Vidya Sagar <vidyas@...dia.com>
> >> Acked-by: Gustavo Pimentel <gustavo.pimentel@...opsys.com>
> >> ---
> >> Changes from [v3]:
> >> * Rebased to linux-next top of the tree
> >>
> >> Changes from [v2]:
> >> * None
> >>
> >> Changes from [v1]:
> >> * Removed dw_pcie_find_next_ext_capability() API from here and made a
> >>    separate patch for that
> >>
> >>   drivers/pci/controller/dwc/pcie-designware.c | 33 ++++++++++++++++++++
> >>   drivers/pci/controller/dwc/pcie-designware.h |  2 ++
> >
> > You claim this is a "move", but I only see adds.  Where did it move
> > *from*?
> These are supposed to be moved from pcie-designware-ep.c file. That was the case
> with my old patches but when I rebased them onto ToT, I missed the change that
> removes them from pcie-designware-ep.c file. Thanks for catching this. I'll
> address it in the next patch.
>
> >
> > While you're at it, can you add a comment in the code about why we
> > can't use the regular pci_find_capability() interface?  It's really a
> > shame to have to reimplement that.
> Regular pci_find_capability() uses 'struct pci_dev *dev' pointer and can be used
> only after device enumeration is done. Whereas, these APIs are used particularly
> before link up and use 'struct dw_pcie *pci' pointer.

pci_bus_find_capability() can be used without enumerating the devices
if you have a pci_bus. It's probably not worth using here though since
you need this code anyway for endpoint mode.

>
> >
> >>   2 files changed, 35 insertions(+)
> >>
> >> diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
> >> index 8e0081ccf83b..6a98135244d6 100644
> >> --- a/drivers/pci/controller/dwc/pcie-designware.c
> >> +++ b/drivers/pci/controller/dwc/pcie-designware.c
> >> @@ -20,6 +20,39 @@
> >>   #define PCIE_PHY_DEBUG_R1_LINK_UP  (0x1 << 4)
> >>   #define PCIE_PHY_DEBUG_R1_LINK_IN_TRAINING (0x1 << 29)
> >>
> >> +static u8 __dw_pcie_find_next_cap(struct dw_pcie *pci, u8 cap_ptr,
> >> +                              u8 cap)
> >> +{
> >> +    u8 cap_id, next_cap_ptr;
> >> +    u16 reg;
> >> +
> >> +    reg = dw_pcie_readw_dbi(pci, cap_ptr);
> >> +    next_cap_ptr = (reg & 0xff00) >> 8;
> >> +    cap_id = (reg & 0x00ff);
> >> +
> >> +    if (!next_cap_ptr || cap_id > PCI_CAP_ID_MAX)
> >> +            return 0;
> >> +
> >> +    if (cap_id == cap)
> >> +            return cap_ptr;
> >> +
> >> +    return __dw_pcie_find_next_cap(pci, next_cap_ptr, cap);
> >> +}
> >> +
> >> +u8 dw_pcie_find_capability(struct dw_pcie *pci, u8 cap)
> >> +{
> >> +    u8 next_cap_ptr;
> >> +    u16 reg;
> >> +
> >> +    reg = dw_pcie_readw_dbi(pci, PCI_CAPABILITY_LIST);
> >> +    next_cap_ptr = (reg & 0x00ff);
> >> +
> >> +    if (!next_cap_ptr)
> >> +            return 0;
> >> +
> >> +    return __dw_pcie_find_next_cap(pci, next_cap_ptr, cap);
> >> +}
> >> +
> >>   int dw_pcie_read(void __iomem *addr, int size, u32 *val)
> >>   {
> >>      if (!IS_ALIGNED((uintptr_t)addr, size)) {
> >> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> >> index 9ee98ced1ef6..35160b4ce929 100644
> >> --- a/drivers/pci/controller/dwc/pcie-designware.h
> >> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> >> @@ -248,6 +248,8 @@ struct dw_pcie {
> >>   #define to_dw_pcie_from_ep(endpoint)   \
> >>              container_of((endpoint), struct dw_pcie, ep)
> >>
> >> +u8 dw_pcie_find_capability(struct dw_pcie *pci, u8 cap);
> >> +
> >>   int dw_pcie_read(void __iomem *addr, int size, u32 *val);
> >>   int dw_pcie_write(void __iomem *addr, int size, u32 val);
> >>
> >> --
> >> 2.17.1
> >>
>