linux-kernel - Re: [PATCH v4 2/2] PCI: iproc: Add outbound configuration for 32-bit I/O region

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Message-ID: <CABe79T7LwFLST0dwwswv8sdqHcn0T4ked5WtcNpM78XUDUN3Jw@mail.gmail.com>
Date:   Mon, 1 Apr 2019 11:04:48 +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, linux-arm-kernel@...ts.infradead.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 v4 2/2] PCI: iproc: Add outbound configuration for 32-bit
 I/O region

Hi Lorenzo,

Please see my reply below,

On Fri, Mar 29, 2019 at 11:06 PM Lorenzo Pieralisi
<lorenzo.pieralisi@....com> wrote:
>
> On Fri, Mar 01, 2019 at 10:22:16AM +0530, Srinath Mannam wrote:
> > In the present driver outbound window configuration is done to map above
> > 32-bit address I/O regions with corresponding PCI memory range given in
> > ranges DT property.
> >
> > This patch add outbound window configuration to map below 32-bit I/O range
> > with corresponding PCI memory, which helps to access I/O region in ARM
> > 32-bit and one to one mapping of I/O region to PCI memory.
> >
> > Ex:
> > 1. ranges DT property given for current driver is,
> >     ranges = <0x83000000 0x0 0x40000000 0x4 0x00000000 0 0x40000000>;
> >     I/O region address is 0x400000000
> > 2. ranges DT property can be given after this patch,
> >     ranges = <0x83000000 0x0 0x42000000 0x0 0x42000000 0 0x2000000>;
> >     I/O region address is 0x42000000
>
> I was applying this patch but I don't understand the commit log and
> how it matches the code, please explain it to me and I will reword
> it.
Iproc PCIe host controller supports outbound address translation
feature to translate AXI address to PCI bus address.
IO address ranges (AXI and PCI) given through ranges DT property have
to program to controller outbound window registers.
Present driver has the support for only 64bit AXI address. so that
ranges DT property has given as 64bit AXI address and 32 bit
PCI bus address.
But with this patch 32-bit AXI address also could be programmed to
Iproc host controller outbound window registers. so that ranges
DT property can have 32bit AXI address which can map to 32-bit PCI bus address.
Example given in commit log is describing ranges DT property changes
with and without this patch.
In the case, without this patch AXI address is more than 32bit
"0x400000000". and with this patch AXI address is 32-bit "0x42000000".
PCI bus address is 32 bit address in both the cases "0x40000000" and 0x42000000.

Regards,
Srinath.
> Thanks,
> Lorenzo
>
> > 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>
> > ---
> >  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
> > +                      */
> > +                     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
> >