linux-kernel - Re: [PATCH v16 0/9] LPC: legacy ISA I/O support

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Date:   Tue, 6 Mar 2018 11:36:27 +0000
From:   John Garry <john.garry@...wei.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        <mika.westerberg@...ux.intel.com>, <rafael@...nel.org>,
        <lorenzo.pieralisi@....com>, <rjw@...ysocki.net>,
        <hanjun.guo@...aro.org>, <robh+dt@...nel.org>,
        <bhelgaas@...gle.com>, <arnd@...db.de>, <mark.rutland@....com>,
        <olof@...om.net>, <dann.frazier@...onical.com>,
        <andy.shevchenko@...il.com>, <robh@...nel.org>
CC:     <joe@...ches.com>, <benh@...nel.crashing.org>,
        <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-acpi@...r.kernel.org>, <linuxarm@...wei.com>,
        <minyard@....org>, <devicetree@...r.kernel.org>,
        <linux-arch@...r.kernel.org>, <rdunlap@...radead.org>,
        <gregkh@...uxfoundation.org>, <akpm@...ux-foundation.org>,
        <frowand.list@...il.com>, <agraf@...e.de>
Subject: Re: [PATCH v16 0/9] LPC: legacy ISA I/O support

On 06/03/2018 11:21, Andy Shevchenko wrote:
> On Tue, 2018-03-06 at 18:47 +0800, John Garry wrote:
>> This patchset supports the IPMI-bt device attached to the Low-Pin-
>> Count
>> interface implemented on Hisilicon Hip06/Hip07 SoC.
>>                         -----------
>>                         | LPC host|
>>                         |         |
>>                         -----------
>>                              |
>>                 _____________V_______________LPC
>>                   |                       |
>>                   V                       V
>>                                      ------------
>>                                      |  BT(ipmi)|
>>                                      ------------
>>
>> When master accesses those peripherals beneath the Hip06/Hip07 LPC, a
>> specific
>> LPC driver is needed to make LPC host generate the standard LPC I/O
>> cycles with
>> the target peripherals'I/O port addresses. But on curent arm64 world,
>> there is
>> no real I/O accesses. All the I/O operations through in/out accessors
>> are based
>> on MMIO ranges; on Hip06/Hip07 LPC the I/O accesses are performed
>> through driver
>> specific accessors rather than MMIO.
>> To solve this issue and keep the relevant existing peripherals'
>> drivers untouched,
>> this patchset:
>>    - introduces a generic I/O space management framework, logical PIO,
>> to support
>>       I/O operations on host controllers operating either on MMIO
>> buses or on buses
>>      requiring specific driver I/O accessors;
>>    - redefines the in/out accessors to provide a unified interface for
>> both MMIO
>>      and driver specific I/O operations. Using logical PIO, th call of
>> in/out() from
>>      the host children drivers, such as ipmi-si, will be redirected to
>> the
>>      corresponding device-specific I/O hooks to perform the I/O
>> accesses.
>>
>> Based on this patch-set, all the I/O accesses to Hip06/Hip07 LPC
>> peripherals can
>> be supported without any changes on the existing ipmi-si driver.
>>
>> The whole patchset has been tested on Hip07 D05 board both using DTB
>> and ACPI.
>>
>
>> V15 thread here: https://lkml.org/lkml/2018/2/26/584
>
> Thanks for an update.
> Though I answered to previous thread.
>
> Summary: I'm fine with the series as long as maintainers are fine
> (Rafael et al.). On personal side I think that the handler approach is
> better. Details are in v15 thread.

Hi Andy,

Thanks for your input and continued support. As I mentioned in reply in 
v15, the handler support would (or has) faced issues. And Rafael seems 
fine with deferring the probe to the LLDD in Patch #7/9

Anyway, let's wait for any more input.

Much appreciated,
John

>