linux-kernel - Re: [PATCH v2 2/2] PCI: iproc: Add PCIe 32bit outbound memory configuration

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Message-ID: <CABe79T6L5mCc5zoyRUD-bPk7UdxOv_Yz3vyUNYg=Edw-u2mGzQ@mail.gmail.com>
Date:   Wed, 13 Feb 2019 10:21:55 +0530
From:   Srinath Mannam <srinath.mannam@...adcom.com>
To:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>, Ray Jui <rjui@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>,
        BCM Kernel Feedback <bcm-kernel-feedback-list@...adcom.com>,
        linux-pci@...r.kernel.org, iommu@...ts.linux-foundation.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Abhishek Shah <abhishek.shah@...adcom.com>,
        Ray Jui <ray.jui@...adcom.com>
Subject: Re: [PATCH v2 2/2] PCI: iproc: Add PCIe 32bit outbound memory configuration

Hi Lorenzo,

Thanks for review, please see my comments below inline.

On Wed, Feb 13, 2019 at 12:07 AM Lorenzo Pieralisi
<lorenzo.pieralisi@....com> wrote:
>
> On Tue, Feb 05, 2019 at 10:27:01AM +0530, Srinath Mannam wrote:
> > Add configuration to support IPROC PCIe host controller outbound memory
> > window mapping with SOC address range inside 4GB boundary, which is 32 bit
> > AXI address.
>
> I do not understand what this means, explain it to me and rewrite the
> commit log accordingly.
>
This is about "I/O regions" addressing given through ranges DT property.
In the current driver "I/O regions" address mapping to corresponding
PCI memory address in controller outbound registers
is supports above 32-bit address.
> What does this solve ? Why do we need this patch or rephrased, what
> is missing in the current driver ?
With this patch, If ranges DT property has below 32-bit I/O regions
address then it will be added in the outbound mapping.
This will help to access I/O region from CPU in 32-bit.
I will update commit log and send next patch set.
Ex:
1. ranges DT property for current driver is,
    ranges = <0x83000000 0x0 0x40000000 0x4 0x00000000 0 0x40000000>;
    I/O region address is 0x400000000
2. ranges DT property with this patch,
    ranges = <0x83000000 0x0 0x42000000 0x0 0x42000000 0 0x2000000>;
    I/O region address is 0x42000000

Regards,
Srinath.
>
> > Signed-off-by: Srinath Mannam <srinath.mannam@...adcom.com>
> > Signed-off-by: Abhishek Shah <abhishek.shah@...adcom.com>
> > Signed-off-by: Ray Jui <ray.jui@...adcom.com>
> > Reviewed-by: Scott Branden <scott.branden@...adcom.com>
> > Reviewed-by: Vikram Prakash <vikram.prakash@...adcom.com>
>
> Review tags should be given on public mailing lists, these ones seem
> to come from non-public review cycles in which case you must drop
> them.
>
> >  drivers/pci/controller/pcie-iproc.c | 21 +++++++++++++++++++--
> >  1 file changed, 19 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/pci/controller/pcie-iproc.c b/drivers/pci/controller/pcie-iproc.c
> > index b882255..080f142 100644
> > --- a/drivers/pci/controller/pcie-iproc.c
> > +++ b/drivers/pci/controller/pcie-iproc.c
> > @@ -955,8 +955,25 @@ static int iproc_pcie_setup_ob(struct iproc_pcie *pcie, u64 axi_addr,
> >                       resource_size_t window_size =
> >                               ob_map->window_sizes[size_idx] * SZ_1M;
> >
> > -                     if (size < window_size)
> > -                             continue;
> > +                     /*
> > +                      * Keep iterating until we reach the last window and
> > +                      * with the minimal window size at index zero. In this
> > +                      * case, we take a compromise by mapping it using the
> > +                      * minimum window size that can be supported
>
> See above, I do not understand clearly what this means.
>
> Lorenzo
>
> > +                      */
> > +                     if (size < window_size) {
> > +                             if (size_idx > 0 || window_idx > 0)
> > +                                     continue;
> > +
> > +                             /*
> > +                              * For the corner case of reaching the minimal
> > +                              * window size that can be supported on the
> > +                              * last window
> > +                              */
> > +                             axi_addr = ALIGN_DOWN(axi_addr, window_size);
> > +                             pci_addr = ALIGN_DOWN(pci_addr, window_size);
> > +                             size = window_size;
> > +                     }
> >
> >                       if (!IS_ALIGNED(axi_addr, window_size) ||
> >                           !IS_ALIGNED(pci_addr, window_size)) {
> > --
> > 2.7.4
> >