Re: [PATCH v6 1/2] net: brcm: netXtreme driver

Roman Bacik
2021-11-05T22:12:14Z

On Fri, Nov 5, 2021 at 3:04 PM Pali Rohár <pali@kernel.org> wrote:
>
> On Friday 05 November 2021 22:09:47 Pali Rohár wrote:
> > On Friday 05 November 2021 12:54:24 Roman Bacik wrote:
> > > > > + pci_read_word16(bp->pdev,
> > > > > + PCI_SUBSYSTEM_VENDOR_ID,
> > > > > + &bp->subsystem_vendor);
> > > > > + pci_read_word16(bp->pdev, PCI_SUBSYSTEM_ID, &bp-
> > > > >subsystem_device);
> > > > > + pci_read_word16(bp->pdev, PCI_COMMAND, &bp->cmd_reg);
> > > > > + pci_read_byte(bp->pdev, PCICFG_ME_REGISTER, &bp->pf_num);
> > > >
> > > > PCICFG_ME_REGISTER looks like an error as there is no such PCI config
> > > > space macro. What you are trying to read into pf_num? Currently I do not
> > > > know what "pf" abbreviation could mean.
> > >
> > > PF stands for physical function and pf_num is the number of physical
> > > functions configured.
> > > The macro is defined in bnxt.h:
> > > #define PCICFG_ME_REGISTER 0x98
> >
> > pci_read_byte() reads from PCI(e) config space, which is standardized.
> > Therefore only standard macro constants from include/pci.h should be
> > used. Standard PCI config header is 64 byte long and after that is
> > linked list of capabilities. Order of capabilities is not defined.
> > Extended capabilities from linked list should be located by macro
> > constants PCI_CAP_ID_*.
> >
> > So above register is part of some extended capability. Correctly it
> > should be used some function to locate starting offset of that extended
> > capability based on PCI_CAP_ID_* (see pci.h file for these functions)
> > and then access that register as offset + PCI_* constant (which defined
> > as relative to the start of extended capability). In case standard macro
> > for this constant in pci.h is missing, it is a good idea to define it,
> > or copy it from linux header file pci_regs.h (to have consistent naming
> > of macros).
>
> Just one example how to read PCIe Link Control Register (to make it
> clear what I mean):
>
> int ret;
> u16 lnkctl;
> int pci_exp_off;
> pci_exp_off = dm_pci_find_capability(dev, PCI_CAP_ID_EXP);
> if (!pci_exp_off) return -ENOENT;
> ret = dm_pci_read_config16(dev, pci_exp_off + PCI_EXP_LNKCTL, &lnkctl);
> if (ret) return ret;

The driver should work for 0x14e4:0x16F0 and we usually test it with
this one. We will use your recommended method if needed. We will try
to remove it in v8, since I do not see bp->pf_num being used.

Thank you very much,

Roman