From: John Syne <john3909@gmail.com>
To: Mugunthan V N <mugunthanvnm@ti.com>
Cc: Lee Jones <lee.jones@linaro.org>,
linux-iio@vger.kernel.org, Tony Lindgren <tony@atomide.com>,
Jonathan Cameron <jic23@kernel.org>, Vignesh R <vigneshr@ti.com>,
linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, Sekhar Nori <nsekhar@ti.com>,
Peter Ujfalusi <peter.ujfalusi@ti.com>
Subject: Re: [PATCH] drivers: mfd: ti_am335x_tscadc: increase ADC ref clock to 24MHz
Date: Mon, 24 Oct 2016 13:58:55 -0700 [thread overview]
Message-ID: <038C6B01-8443-4321-9C65-BAC4095237D3@gmail.com> (raw)
In-Reply-To: <20161024060226.4170-1-mugunthanvnm@ti.com>
> On Oct 23, 2016, at 11:02 PM, Mugunthan V N <mugunthanvnm@ti.com> wrote:
>
> Increase ADC reference clock from 3MHz to 24MHz so that the
> sampling rates goes up from 100K samples per second to 800K
> samples per second on AM335x and AM437x SoC.
>
> Also increase opendelay for touchscreen configuration to
> equalize the increase in ADC reference clock frequency,
> which results in the same amount touch events reported via
> evtest on AM335x GP EVM.
>
> Signed-off-by: Mugunthan V N <mugunthanvnm@ti.com>
> ---
>
> This patch depends on ADC DMA patch series [1]
>
> Without DMA support, when ADC ref clock is set at 24MHz, I am
> seeing fifo overflow as CPU is not able to pull the ADC samples.
> This answers that DMA support is must for ADC to consume the
> samples generated at 24MHz with no open, step delay or
> averaging with patch [2].
>
> Measured the performance with the iio_generic_buffer with the
> patch [3] applied
>
> [1] - http://www.spinics.net/lists/devicetree/msg145045.html
> [2] - http://pastebin.ubuntu.com/23357935/
> [3] - http://pastebin.ubuntu.com/23357939/
>
> ---
> include/linux/mfd/ti_am335x_tscadc.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/mfd/ti_am335x_tscadc.h b/include/linux/mfd/ti_am335x_tscadc.h
> index b9a53e0..96c4207 100644
> --- a/include/linux/mfd/ti_am335x_tscadc.h
> +++ b/include/linux/mfd/ti_am335x_tscadc.h
> @@ -90,7 +90,7 @@
> /* Delay register */
> #define STEPDELAY_OPEN_MASK (0x3FFFF << 0)
> #define STEPDELAY_OPEN(val) ((val) << 0)
> -#define STEPCONFIG_OPENDLY STEPDELAY_OPEN(0x098)
Wouldn’t this be better to add this to the devicetree?
ti,chan-step-avg = <0x16 0x16 0x16 0x16 0x16 0x16 0x16>;
ti,chan-step-opendelay = <0x500 0x500 0x500 0x500 0x500 0x500 0x500>;
ti,chan-step-sampledelay = <0x0 0x0 0x0 0x0 0x0 0x0 0x0>;
Regards,
John
> +#define STEPCONFIG_OPENDLY STEPDELAY_OPEN(0x500)
> #define STEPDELAY_SAMPLE_MASK (0xFF << 24)
> #define STEPDELAY_SAMPLE(val) ((val) << 24)
> #define STEPCONFIG_SAMPLEDLY STEPDELAY_SAMPLE(0)
> @@ -137,7 +137,7 @@
> #define SEQ_STATUS BIT(5)
> #define CHARGE_STEP 0x11
>
> -#define ADC_CLK 3000000
> +#define ADC_CLK 24000000
> #define TOTAL_STEPS 16
> #define TOTAL_CHANNELS 8
> #define FIFO1_THRESHOLD 19
> --
> 2.10.1.502.g6598894
>
next prev parent reply other threads:[~2016-10-24 20:59 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-24 6:02 [PATCH] drivers: mfd: ti_am335x_tscadc: increase ADC ref clock to 24MHz Mugunthan V N
2016-10-24 20:58 ` John Syne [this message]
2016-10-25 5:52 ` Mugunthan V N
2016-10-25 6:01 ` John Syne
2016-10-25 6:16 ` John Syne
2016-10-25 6:37 ` Vignesh R
2016-10-25 15:39 ` John Syne
2016-10-25 6:38 ` Lee Jones
2016-10-25 15:47 ` John Syne
2016-10-26 8:48 ` Lee Jones
2016-10-27 21:17 ` John Syne
2016-10-31 11:39 ` Vignesh R
2016-11-09 23:53 ` John Syne
2016-11-10 5:07 ` Vignesh R
2016-11-11 3:30 ` John Syne
2016-11-11 6:17 ` Vignesh R
2016-10-27 11:20 ` Mugunthan V N
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