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SubjectRe: [PATCH v4] i2c: i801: Register optional lis3lv02d I2C device on Dell machines
Hi!

On Thursday 06 June 2019 16:53:09 Jean Delvare wrote:
> Hi Pali,
>
> On Wed, 5 Jun 2019 00:33:03 +0200, Pali Rohár wrote:
> > Dell platform team told us that some (DMI whitelisted) Dell Latitude
> > machines have ST microelectronics accelerometer at I2C address 0x29.
> >
> > Presence of that ST microelectronics accelerometer is verified by existence
> > of SMO88xx ACPI device which represent that accelerometer. Unfortunately
> > ACPI device does not specify I2C address.
> >
> > This patch registers lis3lv02d device for selected Dell Latitude machines
> > at I2C address 0x29 after detection. And for Dell Vostro V131 machine at
> > I2C address 0x1d which was manually detected.
> >
> > Finally commit a7ae81952cda ("i2c: i801: Allow ACPI SystemIO OpRegion to
> > conflict with PCI BAR") allowed to use i2c-i801 driver on Dell machines so
> > lis3lv02d correctly initialize accelerometer.
> >
> > Tested on Dell Latitude E6440.
> >
> > Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
> >
> > ---
> > Changes since v3:
> > * Use char * [] type for list of acpi ids
> > * Check that SMO88xx acpi device is present, enabled and functioning
> > * Simplify usage of acpi_get_devices()
> > * Change i2c to I2C
> > * Make dell_lis3lv02d_devices const
> >
> > Changes since v2:
> > * Use explicit list of SMOxx ACPI devices
> >
> > Changes since v1:
> > * Added Dell Vostro V131 based on Michał Kępień testing
> > * Changed DMI product structure to include also i2c address
> > ---
> > drivers/i2c/busses/i2c-i801.c | 123 ++++++++++++++++++++++++++++++++++++
> > drivers/platform/x86/dell-smo8800.c | 1 +
> > 2 files changed, 124 insertions(+)
> >
> > diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
> > index ac7f7817dc89..9060d4b16f4f 100644
> > --- a/drivers/i2c/busses/i2c-i801.c
> > +++ b/drivers/i2c/busses/i2c-i801.c
> > @@ -1134,6 +1134,126 @@ static void dmi_check_onboard_devices(const struct dmi_header *dm, void *adap)
> > }
> > }
> >
> > +/* NOTE: Keep this list in sync with drivers/platform/x86/dell-smo8800.c */
> > +static const char *const acpi_smo8800_ids[] = {
> > + "SMO8800",
> > + "SMO8801",
> > + "SMO8810",
> > + "SMO8811",
> > + "SMO8820",
> > + "SMO8821",
> > + "SMO8830",
> > + "SMO8831",
> > +};
> > +
> > +static acpi_status check_acpi_smo88xx_device(acpi_handle obj_handle,
> > + u32 nesting_level,
> > + void *context,
> > + void **return_value)
> > +{
> > + struct acpi_device_info *info;
> > + unsigned long long sta;
> > + acpi_status status;
> > + char *hid;
> > + int i;
> > +
> > + status = acpi_bus_get_status_handle(obj_handle, &sta);
> > + if (!ACPI_SUCCESS(status))
> > + return AE_OK;
> > + if (!(sta & (ACPI_STA_DEVICE_PRESENT |
> > + ACPI_STA_DEVICE_ENABLED |
> > + ACPI_STA_DEVICE_FUNCTIONING)))
> > + return AE_OK;
>
> This is testing that *either* bit is set. Is it what you intend to
> achieve, or would you rather want to ensure that *all* these bits are
> set?

Of course, it is wrong. Thanks for catch. We should ignore apci devices
which are not present, which are disabled or which are not functioning.

Now I looked into acpi_get_devices() implementation and it call
acpi_ns_get_device_callback() function callback for every device. At the
end that function calls user supplied check_acpi_smo88xx_device
function.

And acpi_ns_get_device_callback() already ignores acpi devices which do
not have ACPI_STA_DEVICE_PRESENT or ACPI_STA_DEVICE_FUNCTIONING flag.

According to acpi documentation when ACPI_STA_DEVICE_PRESENT is not set
then ACPI_STA_DEVICE_ENABLED also cannot be set.

So the whole acpi_bus_get_status_handle() is not needed at all as
acpi_get_devices() via acpi_ns_get_device_callback() already filter
unsuitable acpi devices.

I guess that I already did this investigation in past and added comment
"exists and is enabled" which is below near acpi_get_devices() call. But
as I wrote this patch more then year ago I forgot about it.

I will remove that check. Do you have any suggestion what to write into
comment so other readers in future would know that we do not need to
check anything with _STA acpi method?

> > +
> > + status = acpi_get_object_info(obj_handle, &info);
> > + if (!ACPI_SUCCESS(status) || !(info->valid & ACPI_VALID_HID))
> > + return AE_OK;
> > +
> > + hid = info->hardware_id.string;
> > + if (!hid)
> > + return AE_OK;
> > +
> > + for (i = 0; i < ARRAY_SIZE(acpi_smo8800_ids); ++i) {
> > + if (strcmp(hid, acpi_smo8800_ids[i]) == 0) {
> > + *((bool *)return_value) = true;
> > + return AE_CTRL_TERMINATE;
> > + }
> > + }
> > +
> > + return AE_OK;
> > +}
> > +
> > +static bool is_dell_system_with_lis3lv02d(void)
> > +{
> > + bool found;
> > + const char *vendor;
> > +
> > + vendor = dmi_get_system_info(DMI_SYS_VENDOR);
> > + if (strcmp(vendor, "Dell Inc.") != 0)
> > + return false;
> > +
> > + /*
> > + * Check that ACPI device SMO88xx exists and is enabled. That ACPI
> > + * device represent our ST microelectronics lis3lv02d accelerometer but
> > + * unfortunately without any other information (like I2C address).
> > + */
> > + found = false;
> > + acpi_get_devices(NULL, check_acpi_smo88xx_device, NULL,
> > + (void **)&found);
>
> Alignment is incorrect now - but don't resend just for this.
>
> > +
> > + return found;
> > +}
> > (...)
>
> Everything else looks good to me now. Has the latest version of your
> patch been tested on real hardware?

Yes, I'm testing it on E6440 machine which is still in use (it is nice
piece from Dell). Otherwise I would not spend time on this patch after
such long time :-)

--
Pali Rohár
pali.rohar@gmail.com
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