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SubjectRe: [PATCH] input: goodix: Poll the 'buffer status' bit before reading data
Hi,

Le 2017-03-31 00:48, Dmitry Torokhov a écrit :
> On Thu, Mar 30, 2017 at 03:33:49PM +0200, Paul Cercueil wrote:
>> The Goodix panel triggers an interrupt on touch events. However, its
>> registers will contain the valid values a short time after the
>> interrupt, and not when it's raised. At that moment, the 'buffer
>> status'
>> bit is set.
>
> Yay for awesome hardware.
>
>>
>> Previously, if the 'buffer status' bit was not set when the registers
>> were read, the data was discarded and no input event was emitted,
>> causing "finger down" or "finger up" events to be missed sometimes.
>>
>> This went unnoticed until v4.9, as the DesignWare I2C driver commonly
>> used with this driver had enough latency for that bug to never
>> trigger.
>>
>> Now, in the IRQ handler we will poll (with a timeout) the 'buffer
>> status'
>> bit and process the data of the panel as soon as this bit gets set.
>>
>> Note that the Goodix panel will send a few spurious interrupts after
>> the
>> 'finger up' event, in which the 'buffer status' bit will never be set.
>>
>> Signed-off-by: Paul Cercueil <paul@crapouillou.net>
>> ---
>> drivers/input/touchscreen/goodix.c | 30
>> +++++++++++++++++++++++-------
>> 1 file changed, 23 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/input/touchscreen/goodix.c
>> b/drivers/input/touchscreen/goodix.c
>> index 240b16f3ee97..7a8b89b87c2f 100644
>> --- a/drivers/input/touchscreen/goodix.c
>> +++ b/drivers/input/touchscreen/goodix.c
>> @@ -195,18 +195,34 @@ static int goodix_get_cfg_len(u16 id)
>>
>> static int goodix_ts_read_input_report(struct goodix_ts_data *ts, u8
>> *data)
>> {
>> + unsigned int timeout = 100;
>> int touch_num;
>> int error;
>>
>> - error = goodix_i2c_read(ts->client, GOODIX_READ_COOR_ADDR, data,
>> + /* The 'buffer status' bit, which indicates that the data is valid,
>> is
>> + * not set as soon as the interrupt is raised, but slightly after.
>> + */
>> + do {
>> + error = goodix_i2c_read(ts->client, GOODIX_READ_COOR_ADDR, data,
>> GOODIX_CONTACT_SIZE + 1);
>> - if (error) {
>> - dev_err(&ts->client->dev, "I2C transfer error: %d\n", error);
>> - return error;
>> - }
>> + if (error) {
>> + dev_err(&ts->client->dev, "I2C transfer error: %d\n",
>> + error);
>> + return error;
>> + }
>>
>> - if (!(data[0] & 0x80))
>> - return -EAGAIN;
>> + if (data[0] & 0x80)
>> + break;
>> +
>> + usleep_range(100, 200);
>
> What is the typical delay between IRQ and data being ready? 100 repeats
> suggest that poll interval is too small.
>

On my panel it seems to be about 10ms - which sounds like a *huge* lot
of time...

>> + } while (--timeout);
>> +
>> + if (!timeout) {
>> + /* The Goodix panel will send spurious interrupts after a
>> + * 'finger up' event, which will always cause a timeout.
>> + */
>> + return 0;
>> + }
>>
>> touch_num = data[0] & 0x0f;
>> if (touch_num > ts->max_touch_num)
>> --
>> 2.11.0
>>
>
> Thanks.

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