linux-kernel - Re: [PATCH v13 7/9] ACPI: Translate the I/O range of non-MMIO devices before scanning

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Message-ID: <e3fb78b3-5f5c-fe96-9f02-e96092963c17@huawei.com>
Date:   Thu, 15 Feb 2018 11:19:00 +0000
From:   John Garry <john.garry@...wei.com>
To:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>, <rafael@...nel.org>
CC:     <mika.westerberg@...ux.intel.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>, <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>
Subject: Re: [PATCH v13 7/9] ACPI: Translate the I/O range of non-MMIO devices
 before scanning

> Nothing apart from only being used by arm64 platforms today, which is
> circumstantial.
>
>>
>> I understand you need to find a place to add the:
>>
>> acpi_indirect_io_scan_init()
>>
>> to be called from core ACPI code because ACPI can't handle probe
>> dependencies in any other way but other than that this patch is
>> a Hisilicon ACPI driver - there is nothing generic in it (or at
>> least there are no standard bindings to make it so).
>>
>> Whether a callback from ACPI core code (acpi_scan_init()) to a driver
>> specific hook is sane or not that's the question and the only reason
>> why you want to add this in drivers/acpi/arm64 rather than, say,
>> drivers/bus (as you do for the DT driver).
>>
>> I do not know Rafael's opinion on the above, I would like to help
>> you make forward progress but please understand my concerns, mostly
>> on FW side.
>>
>
> I did mention an alternative in my "ping" in v12 patch 7/9 (Feb 1), but
> no response to this specific note so I kept on the same path.
>
> Here's what I then wrote:
> "I think another solution - which you may prefer - is to avoid adding
> this scan handler (and all this other scan code) and add a check like
> acpi_is_serial_bus_slave() [which checks the device parent versus a list
> of known indirectIO hosts] to not enumerate these children, and do it
> from the LLDD host probe instead (https://lkml.org/lkml/2017/6/16/250)"
>

Hi Rafael, Lorenzo,

I can avoid adding the scan handler in acpi_indirectio.c by skipping the 
child enumeration, like with this change in scan.c:

+static const struct acpi_device_id indirect_io_hosts[] = {
+    {"HISI0191", 0},    /* HiSilicon LPC host */
+    {},
+};
+
+static bool acpi_is_indirect_io_slave(struct acpi_device *device)
+{
+    struct acpi_device *parent = dev->parent;
+
+    if (!parent || acpi_match_device_ids(parent, indirect_io_hosts))
+        return false;
+
+    return true;
+}
+
  static bool acpi_is_serial_bus_slave(struct acpi_device *device)
  {
      struct list_head resource_list;
      bool is_serial_bus_slave = false;

+    if (acpi_is_indirect_io_slave(device))
+        return true;
+
      /* Macs use device properties in lieu of _CRS resources */


This means I can move all this scan code into the LLDD.

What do you think? Please let me know.

John