From: Ray Jui <ray.jui@broadcom.com>
To: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
Srinath Mannam <srinath.mannam@broadcom.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>, Ray Jui <rjui@broadcom.com>,
Scott Branden <sbranden@broadcom.com>,
BCM Kernel Feedback <bcm-kernel-feedback-list@broadcom.com>,
linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Abhishek Shah <abhishek.shah@broadcom.com>
Subject: Re: [PATCH v4 2/2] PCI: iproc: Add outbound configuration for 32-bit I/O region
Date: Thu, 4 Apr 2019 10:48:08 -0700 [thread overview]
Message-ID: <2c3d80ce-6fa8-a20b-135b-ea754ff4eda5@broadcom.com> (raw)
In-Reply-To: <20190403113124.GA16233@e107981-ln.cambridge.arm.com>
Hi Lorenzo,
On 4/3/2019 4:31 AM, Lorenzo Pieralisi wrote:
> On Wed, Apr 03, 2019 at 08:41:44AM +0530, Srinath Mannam wrote:
>> Hi Lorenzo,
>>
>> Please see my reply below,
>>
>> On Tue, Apr 2, 2019 at 7:08 PM Lorenzo Pieralisi
>> <lorenzo.pieralisi@arm.com> wrote:
>>>
>>> On Tue, Apr 02, 2019 at 04:16:13PM +0530, Srinath Mannam wrote:
>>>
>>> [...]
>>>
>>>>> Ok - I start to understand. What does it mean in HW terms that your
>>>>> 32bit AXI address region size is 32MB ? Please explain to me in details.
>>>>>
>>>> In our PCIe controller HW, AXI address from 0x42000000 to 0x44000000
>>>> of 32MB size and .
>>>> AXI address from 0x400000000 to 0x480000000 of 2GB size are provided
>>>> to map ob address.
>>>> First IO region is inside 32bit address and second IO region is
>>>> outside 32bit address.
>>>> This code change is to map first IO region(0x42000000 to 0x44000000).
>>>>
>>>>> IIUC you are using an OARR0 of 128MB in size to map a 32MB address
>>>>> region, that's what I understand this patch does (and the lowest index
>>>>> corresponds to the smallest possible size - it is far from clear by
>>>>> looking at the patch).
>>>> Yes, lowest index corresponds to smallest possible size (128MB).
>>>> In our controller we have multiple windows like OARR0, OARR1, OARR2,
>>>> OARR3 all supports multiple sizes from 128MB to 1024MB.
>>>> These details are given at the top of this driver file, as shown
>>>> below. all windows supports 128MB size still we must use OARR0 window
>>>> to configure first IO region(0x42000000 to 0x44000000).
>>>>
>>>> static const struct iproc_pcie_ob_map paxb_v2_ob_map[] = {
>>>> {
>>>> /* OARR0/OMAP0 */
>>>> .window_sizes = { 128, 256 },
>>>> .nr_sizes = 2,
>>>> },
>>>> {
>>>> /* OARR1/OMAP1 */
>>>> .window_sizes = { 128, 256 },
>>>> .nr_sizes = 2,
>>>> },
>>>> {
>>>> /* OARR2/OMAP2 */
>>>> .window_sizes = { 128, 256, 512, 1024 },
>>>> .nr_sizes = 4,
>>>> },
>>>> {
>>>> /* OARR3/OMAP3 */
>>>> .window_sizes = { 128, 256, 512, 1024 },
>>>> .nr_sizes = 4,
>>>> },
>>>> };
>>>
>>> Ok so this patch allows mapping an AXI I/O window that is smaller
>>> than OARR possible sizes, why it was not done from the beginning
>>> I really do not know.
>>>
>> Same Iproc driver we use for multiple SOCs, in previous SOCs does not
>> have 32-bit AXI address region to map ob.
>> In the present SOC, 32-bit AXI address region is available so that
>> this change is added.
>>
>>> Now explain this to me please:
>>>
>>>> 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
>>>
>>> Why 1:1 AXI<->PCI address mapping is not possible in (1), how does the
>>> current code works on 32-bit systems and what's the benefit your change
>>> is bringing.
>> non-prefetchable memory range can only support 32-bit addresses, so
>> that we have taken 32-bit PCI bus address in (1).
>> current code does not work in 32-bit systems. In the present SOC with
>> this new change we can access from 32-bit CPU.
>
> Thank you. I rewrote the log and pushed patches to pci/iproc, please
> have a look (Ray/Scott please do have a look too) and report back
> if that's fine.>
I reviewed the rephrased commit message by you in pci/iproc branch. It
looks very good to me. Thank you so much for helping with this!
Ray
> Do you agree that the initial commit was lacking _significant_
> information ? Please remember that the commit log plays a fundamental
> part in understanding a change and this one is a very important one
> so I am being pedantic on it.
>
> Thanks,
> Lorenzo
>
next prev parent reply other threads:[~2019-04-04 17:48 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-01 4:52 [PATCH v4 0/2] Add IPROC PCIe new features Srinath Mannam
2019-03-01 4:52 ` [PATCH v4 1/2] PCI: iproc: Add CRS check in config read Srinath Mannam
2019-03-01 4:52 ` [PATCH v4 2/2] PCI: iproc: Add outbound configuration for 32-bit I/O region Srinath Mannam
2019-03-29 17:35 ` Lorenzo Pieralisi
2019-04-01 5:34 ` Srinath Mannam
2019-04-01 16:44 ` Lorenzo Pieralisi
2019-04-01 22:03 ` Ray Jui
2019-04-02 9:50 ` Srinath Mannam
2019-04-02 10:26 ` Lorenzo Pieralisi
2019-04-02 10:46 ` Srinath Mannam
2019-04-02 13:38 ` Lorenzo Pieralisi
2019-04-03 3:11 ` Srinath Mannam
2019-04-03 11:31 ` Lorenzo Pieralisi
2019-04-04 5:41 ` Srinath Mannam
2019-04-04 17:48 ` Ray Jui [this message]
2019-03-27 8:38 ` [PATCH v4 0/2] Add IPROC PCIe new features Srinath Mannam
2019-03-27 12:31 ` Lorenzo Pieralisi
2019-03-27 15:15 ` Srinath Mannam
2019-03-29 16:51 ` Lorenzo Pieralisi
2019-03-29 17:03 ` Scott Branden
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=2c3d80ce-6fa8-a20b-135b-ea754ff4eda5@broadcom.com \
--to=ray.jui@broadcom.com \
--cc=abhishek.shah@broadcom.com \
--cc=bcm-kernel-feedback-list@broadcom.com \
--cc=bhelgaas@google.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pci@vger.kernel.org \
--cc=lorenzo.pieralisi@arm.com \
--cc=rjui@broadcom.com \
--cc=sbranden@broadcom.com \
--cc=srinath.mannam@broadcom.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).