From: Jarkko Nikula <jarkko.nikula@linux.intel.com>
To: Sultan Alsawaf <sultan@kerneltoast.com>,
Aaron Ma <aaron.ma@canonical.com>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Benjamin Tissoires <benjamin.tissoires@redhat.com>,
Hans de Goede <hdegoede@redhat.com>,
HungNien Chen <hn.chen@weidahitech.com>,
Jiri Kosina <jikos@kernel.org>,
Kai-Heng Feng <kai.heng.feng@canonical.com>,
linux-i2c@vger.kernel.org, linux-input@vger.kernel.org,
linux-kernel@vger.kernel.org,
Mika Westerberg <mika.westerberg@linux.intel.com>,
Pavel Balan <admin@kryma.net>, Tin Huynh <tnhuynh@apm.com>,
Wolfram Sang <wsa@kernel.org>,
You-Sheng Yang <vicamo.yang@canonical.com>
Subject: Re: [PATCH 2/2] HID: i2c-hid: Use block reads when possible to save power
Date: Tue, 16 Jun 2020 16:43:43 +0300 [thread overview]
Message-ID: <c4373272-e656-773c-dfd2-0efc4c53c92d@linux.intel.com> (raw)
In-Reply-To: <20200614210255.4641-3-sultan@kerneltoast.com>
On 6/15/20 12:02 AM, Sultan Alsawaf wrote:
> From: Sultan Alsawaf <sultan@kerneltoast.com>
>
> We have no way of knowing how large an incoming payload is going to be,
> so the only strategy available up until now has been to always retrieve
> the maximum possible report length over i2c, which can be quite
> inefficient. For devices that send reports in block read format, the i2c
> controller driver can read the payload length on the fly and terminate
> the i2c transaction early, resulting in considerable power savings.
>
> On a Dell Precision 15 5540 with an i9-9880H, resting my finger on the
> touchpad causes psys power readings to go up by about 4W and hover there
> until I remove my finger. With this patch, my psys readings go from 4.7W
> down to 3.1W, yielding about 1.6W in savings. This is because my
> touchpad's max report length is 60 bytes, but all of the regular reports
> it sends for touch events are only 32 bytes, so the i2c transfer is
> roughly halved for the common case.
>
> Signed-off-by: Sultan Alsawaf <sultan@kerneltoast.com>
> ---
> drivers/hid/i2c-hid/i2c-hid-core.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/hid/i2c-hid/i2c-hid-core.c b/drivers/hid/i2c-hid/i2c-hid-core.c
> index 294c84e136d7..4b507de48d70 100644
> --- a/drivers/hid/i2c-hid/i2c-hid-core.c
> +++ b/drivers/hid/i2c-hid/i2c-hid-core.c
> @@ -476,7 +476,8 @@ static void i2c_hid_get_input(struct i2c_hid *ihid)
> if (size > ihid->bufsize)
> size = ihid->bufsize;
>
> - ret = i2c_master_recv(ihid->client, ihid->inbuf, size);
> + ret = i2c_transfer_buffer_flags(ihid->client, ihid->inbuf, size,
> + I2C_M_RD | I2C_M_RECV_LEN);
This causes i2c-hid compatible touchscreen to stop working for me.
Ok (with patch 1/2)
[ 9.346134] i2c_hid i2c-ELAN221D:00: Fetching the HID descriptor
[ 9.346141] i2c_hid i2c-ELAN221D:00: __i2c_hid_command: cmd=01 00
[ 9.362082] i2c_hid i2c-ELAN221D:00: HID Descriptor: 1e 00 00 01 31
02 02 00 03 00 43 00 04 00 ff 00 05 00 06 00 f3 04 1d 22 10 56 00 00 00 00
[ 9.385897] i2c_hid i2c-ELAN221D:00: entering i2c_hid_parse
[ 9.386547] i2c_hid i2c-ELAN221D:00: i2c_hid_hwreset
[ 9.386598] i2c_hid i2c-ELAN221D:00: i2c_hid_set_power
[ 9.386616] i2c_hid i2c-ELAN221D:00: __i2c_hid_command: cmd=05 00 00 08
[ 9.391595] i2c_hid i2c-ELAN221D:00: resetting...
[ 9.408864] i2c_hid i2c-ELAN221D:00: __i2c_hid_command: cmd=05 00 00 01
[ 9.410162] i2c_hid i2c-ELAN221D:00: __i2c_hid_command: waiting...
[ 9.418223] i2c_hid i2c-ELAN221D:00: __i2c_hid_command: finished.
[ 9.418231] i2c_hid i2c-ELAN221D:00: i2c_hid_set_power
[ 9.418236] i2c_hid i2c-ELAN221D:00: __i2c_hid_command: cmd=05 00 00 08
[ 9.418531] i2c_hid i2c-ELAN221D:00: asking HID report descriptor
[ 9.418537] i2c_hid i2c-ELAN221D:00: __i2c_hid_command: cmd=02 00
[ 9.440093] i2c_hid i2c-ELAN221D:00: Report Descriptor: 05 0d 09 04
a1 01 85 01 09 22 a1 02 09 42 15 00 25 01 75 01 95 01 81 02 75 01 81 03
75 06 09 51 25 3f 81 02 26 ff 00 75 08 09 48 81 02 09 49 81 02 95 01 05
01 a4 26 c0 0c 75 10 55 0f 65 11 09
Not ok (with patches 1-2/2)
[ 9.428690] i2c_hid i2c-ELAN221D:00: Fetching the HID descriptor
[ 9.428698] i2c_hid i2c-ELAN221D:00: __i2c_hid_command: cmd=01 00
[ 9.430017] i2c_hid i2c-ELAN221D:00: HID Descriptor: 1e 00 00 01 31
02 02 00 03 00 43 00 04 00 ff 00 05 00 06 00 f3 04 1d 22 10 56 00 00 00 00
[ 9.430836] i2c_hid i2c-ELAN221D:00: entering i2c_hid_parse
[ 9.431205] i2c_hid i2c-ELAN221D:00: i2c_hid_hwreset
[ 9.431294] i2c_hid i2c-ELAN221D:00: i2c_hid_set_power
[ 9.431314] i2c_hid i2c-ELAN221D:00: __i2c_hid_command: cmd=05 00 00 08
[ 9.435937] i2c_hid i2c-ELAN221D:00: resetting...
[ 9.435944] i2c_hid i2c-ELAN221D:00: __i2c_hid_command: cmd=05 00 00 01
[ 9.436150] i2c_hid i2c-ELAN221D:00: __i2c_hid_command: waiting...
[ 10.461304] i2c_designware i2c_designware.3: controller timed out
[ 10.498312] i2c_designware i2c_designware.3: timeout in disabling adapter
[ 14.525115] i2c_hid i2c-ELAN221D:00: __i2c_hid_command: finished.
[ 14.525130] i2c_hid i2c-ELAN221D:00: failed to reset device.
[ 14.532507] i2c_hid i2c-ELAN221D:00: i2c_hid_set_power
[ 14.532520] i2c_hid i2c-ELAN221D:00: __i2c_hid_command: cmd=05 00 01 08
[ 14.553027] i2c_designware i2c_designware.3: timeout waiting for bus
ready
...
I don't know what causes the breakage but according to HID Over I2C
Protocol Specification the descriptor length is 16 bits. Maybe the code
misses the last byte and/or the data is off by one byte by taking the
2nd length byte as 1st data byte?
--
Jarkko
next prev parent reply other threads:[~2020-06-16 13:43 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-14 21:02 [PATCH 0/2] i2c-hid: Save power by reducing i2c xfers with block reads Sultan Alsawaf
2020-06-14 21:02 ` [PATCH 1/2] i2c: designware: Only check the first byte for SMBus block read length Sultan Alsawaf
2020-06-15 9:40 ` Andy Shevchenko
2020-06-15 16:03 ` Sultan Alsawaf
2020-06-15 16:07 ` Andy Shevchenko
2020-06-15 17:15 ` Sultan Alsawaf
2020-06-16 13:22 ` Jarkko Nikula
2020-06-16 15:43 ` [PATCH v2] " Sultan Alsawaf
2020-06-17 11:08 ` Jarkko Nikula
2020-06-14 21:02 ` [PATCH 2/2] HID: i2c-hid: Use block reads when possible to save power Sultan Alsawaf
2020-06-16 13:43 ` Jarkko Nikula [this message]
2020-06-16 15:49 ` [PATCH v2] " Sultan Alsawaf
2020-06-16 16:41 ` Andy Shevchenko
2020-06-16 17:18 ` Andi Shyti
2020-06-16 17:32 ` Sultan Alsawaf
2020-06-16 18:02 ` Andi Shyti
2020-06-16 18:17 ` Sultan Alsawaf
2020-06-17 11:17 ` Jarkko Nikula
2020-06-29 17:43 ` Sultan Alsawaf
2020-07-01 8:04 ` Jarkko Nikula
2020-07-01 15:00 ` Sultan Alsawaf
2020-07-03 11:18 ` Jarkko Nikula
2020-09-14 0:15 ` [PATCH v3] i2c: Squash of SMBus block read patchset " Sultan Alsawaf
[not found] ` <bcf9cd02-13d1-8f87-8ef9-2f05f0b54808@linux.intel.com>
2020-09-15 17:48 ` Sultan Alsawaf
2020-09-16 14:09 ` Jarkko Nikula
2020-09-15 20:44 ` Jiri Kosina
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