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Date: Thu, 20 Aug 2015 17:41:30 +0530
From: Vignesh R <vigneshr@...com>
To: Michael Welling <mwelling@...e.org>
CC: Wolfram Sang <wsa@...-dreams.de>,
Dmitry Torokhov <dmitry.torokhov@...il.com>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
Jonathan Cameron <jic23@...nel.org>,
"Griffis, Brad" <bgriffis@...com>
Subject: Re: [PATCH] input: ti_am335x_tsc: Add open delay parameter
On 08/19/2015 11:38 PM, Michael Welling wrote:
> On Wed, Aug 12, 2015 at 01:44:22PM -0500, Michael Welling wrote:
>> On Wed, Aug 12, 2015 at 11:56:36AM +0530, Vignesh R wrote:
>>> Hi Michael,
>>>
>>> + Dmitry
>>>
>>> On 08/12/2015 12:15 AM, Michael Welling wrote:
>>>> Adds a device tree parameter to set the open delay on the touchscreen
>>>> conversion steps. Increasing this parameter helps the touch accuracy on
>>>> some screens.
>>>>
>>>> Signed-off-by: Michael Welling <mwelling@...e.org>
>>>> ---
>>>> .../bindings/input/touchscreen/ti-tsc-adc.txt | 5 +++++
>>>> drivers/input/touchscreen/ti_am335x_tsc.c | 18 ++++++++++++++----
>>>> 2 files changed, 19 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt b/Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt
>>>> index b1163bf..cb11fda 100644
>>>> --- a/Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt
>>>> +++ b/Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt
>>>> @@ -41,6 +41,11 @@ Optional properties:
>>>> charge step, so this does in fact function as a
>>>> hardware knob for adjusting the amount of "settling
>>>> time".
>>>> + ti,open-delay: Open delay applied to all touchscreen conversion steps.
>>>> + The value corresponds to the number of ADC clock
>>>> + cycles to wait after applying the step configuration
>>>> + registers and before sending the start of ADC
>>>> + conversion. Maximum value is 0x3FFFF.
>>>>
>>>
>>> Since open-delay is per step, is it not better to allow specifying
>>> open-delay per step like ti,chan-step-opendelay of adc? This will help
>>> control open-delay for all the four wires.
>>
>> Do you see any reason why you would want a different delay for each step of
>> the conversion on the same touchscreen?
Sorry for the delay,
I haven't seen different delays being used for different channels on
4-wire TSC ( not sure of 5-wire or 8 wire designs). Since this is DT
change, I just wanted to make sure more flexibility is provided.
>>
>> The user would need to know the number of steps what each of the steps do.
>>
What I was thinking was making open-delay configurable per channel (one
entry for X+, X-, Y+, Y-).
For example, for a 4-wire TSC:
ti,chan-open-delay = <0x30 0x100 0x20 0x10>; /* for X+, X-, Y+, Y- */
>>>
>>>> - child "adc"
>>>> ti,chan-step-opendelay: List of open delays for each channel of
>>>> diff --git a/drivers/input/touchscreen/ti_am335x_tsc.c b/drivers/input/touchscreen/ti_am335x_tsc.c
>>>> index 191a1b8..37a9729 100644
>>>> --- a/drivers/input/touchscreen/ti_am335x_tsc.c
>>>> +++ b/drivers/input/touchscreen/ti_am335x_tsc.c
>>>> @@ -54,6 +54,7 @@ struct titsc {
>>>> u32 inp_xp, inp_xn, inp_yp, inp_yn;
>>>> u32 step_mask;
>>>> u32 charge_delay;
>>>> + u32 open_delay;
>>>> };
>>>>
>>>> static unsigned int titsc_readl(struct titsc *ts, unsigned int reg)
>>>> @@ -148,7 +149,7 @@ static void titsc_step_config(struct titsc *ts_dev)
>>>> end_step = first_step + tsc_steps;
>>>> for (i = end_step - ts_dev->coordinate_readouts; i < end_step; i++) {
>>>> titsc_writel(ts_dev, REG_STEPCONFIG(i), config);
>>>> - titsc_writel(ts_dev, REG_STEPDELAY(i), STEPCONFIG_OPENDLY);
>>>> + titsc_writel(ts_dev, REG_STEPDELAY(i), ts_dev->open_delay);
>>>> }
>>>>
>>>> config = 0;
>>>> @@ -172,7 +173,7 @@ static void titsc_step_config(struct titsc *ts_dev)
>>>> end_step = first_step + ts_dev->coordinate_readouts;
>>>> for (i = first_step; i < end_step; i++) {
>>>> titsc_writel(ts_dev, REG_STEPCONFIG(i), config);
>>>> - titsc_writel(ts_dev, REG_STEPDELAY(i), STEPCONFIG_OPENDLY);
>>>> + titsc_writel(ts_dev, REG_STEPDELAY(i), ts_dev->open_delay);
>>>> }
>>>>
>>>> /* Make CHARGECONFIG same as IDLECONFIG */
>>>> @@ -188,13 +189,13 @@ static void titsc_step_config(struct titsc *ts_dev)
>>>> STEPCONFIG_INP(ts_dev->inp_xp);
>>>> titsc_writel(ts_dev, REG_STEPCONFIG(end_step), config);
>>>> titsc_writel(ts_dev, REG_STEPDELAY(end_step),
>>>> - STEPCONFIG_OPENDLY);
>>>> + ts_dev->open_delay);
>>>>
>>>> end_step++;
>>>> config |= STEPCONFIG_INP(ts_dev->inp_yn);
>>>> titsc_writel(ts_dev, REG_STEPCONFIG(end_step), config);
>>>> titsc_writel(ts_dev, REG_STEPDELAY(end_step),
>>>> - STEPCONFIG_OPENDLY);
>>>> + ts_dev->open_delay);
>>>>
>>>> /* The steps end ... end - readouts * 2 + 2 and bit 0 for TS_Charge */
>>>> stepenable = 1;
>>>> @@ -392,6 +393,15 @@ static int titsc_parse_dt(struct platform_device *pdev,
>>>> dev_warn(&pdev->dev, "ti,charge-delay not specified\n");
>>>> }
>>>>
>>>> + err = of_property_read_u32(node, "ti,open-delay",
>>>> + &ts_dev->open_delay);
>>>> + /*
>>>> + * If ti,open-delay value is not specified, then use
>>>> + * STEPCONFIG_OPENDLY as the default value.
>>>> + */
>>>> + if (err < 0)
>>>> + ts_dev->open_delay = STEPCONFIG_OPENDLY;
>>>> +
>>>> return of_property_read_u32_array(node, "ti,wire-config",
>>>> ts_dev->config_inp, ARRAY_SIZE(ts_dev->config_inp));
>>>> }
>>>>
>>>
>>> --
>>> Regards
>>> Vignesh
--
Regards
Vignesh
--
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