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Message-ID: <52B72584.5090608@kernel.org>
Date: Sun, 22 Dec 2013 17:46:44 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
Lee Jones <lee.jones@...aro.org>,
Samuel Ortiz <sameo@...ux.intel.com>
CC: Dmitry Torokhov <dmitry.torokhov@...il.com>,
Zubair Lutfullah <zubair.lutfullah@...il.com>,
Felipe Balbi <balbi@...com>, linux-iio@...r.kernel.org,
linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] mfd: ti_am335x_tscadc: Don't read back REG_SE
On 12/19/13 15:28, Sebastian Andrzej Siewior wrote:
> The purpose of reg_se_cache has been defeated. It should avoid the
> read-back of the register to avoid the latency and the fact that the
> bits are reset to 0 after the individual conversation took place.
>
> The reason why this is required like this to work, is that read-back of
> the register removes the bits of the ADC so they do not start another
> conversation after the register is re-written from the TSC side for the
> update.
> To avoid the not required read-back I introduce a "set once" variant which
> does not update the cache mask. After the conversation completes, the
> bit is removed from the SE register anyway and we don't plan a new
> conversation "any time soon". The current set function is renamed to
> set_cache to distinguish the two operations.
> This is a small preparation for a larger sync-rework.
>
> Acked-by: Lee Jones <lee.jones@...aro.org>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Acked-by: Jonathan Cameron <jic23@...nel.org>
> ---
> drivers/iio/adc/ti_am335x_adc.c | 4 ++--
> drivers/input/touchscreen/ti_am335x_tsc.c | 4 ++--
> drivers/mfd/ti_am335x_tscadc.c | 16 ++++++++++++----
> include/linux/mfd/ti_am335x_tscadc.h | 3 ++-
> 4 files changed, 18 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/iio/adc/ti_am335x_adc.c b/drivers/iio/adc/ti_am335x_adc.c
> index e948454..b5197a0 100644
> --- a/drivers/iio/adc/ti_am335x_adc.c
> +++ b/drivers/iio/adc/ti_am335x_adc.c
> @@ -181,7 +181,7 @@ static int tiadc_buffer_postenable(struct iio_dev *indio_dev)
> enb |= (get_adc_step_bit(adc_dev, bit) << 1);
> adc_dev->buffer_en_ch_steps = enb;
>
> - am335x_tsc_se_set(adc_dev->mfd_tscadc, enb);
> + am335x_tsc_se_set_cache(adc_dev->mfd_tscadc, enb);
>
> tiadc_writel(adc_dev, REG_IRQSTATUS, IRQENB_FIFO1THRES
> | IRQENB_FIFO1OVRRUN | IRQENB_FIFO1UNDRFLW);
> @@ -335,7 +335,7 @@ static int tiadc_read_raw(struct iio_dev *indio_dev,
> return -EBUSY;
>
> step_en = get_adc_step_mask(adc_dev);
> - am335x_tsc_se_set(adc_dev->mfd_tscadc, step_en);
> + am335x_tsc_se_set_once(adc_dev->mfd_tscadc, step_en);
>
> /* Wait for ADC sequencer to complete sampling */
> while (tiadc_readl(adc_dev, REG_ADCFSM) & SEQ_STATUS) {
> diff --git a/drivers/input/touchscreen/ti_am335x_tsc.c b/drivers/input/touchscreen/ti_am335x_tsc.c
> index 68beada..2ca5a7b 100644
> --- a/drivers/input/touchscreen/ti_am335x_tsc.c
> +++ b/drivers/input/touchscreen/ti_am335x_tsc.c
> @@ -198,7 +198,7 @@ static void titsc_step_config(struct titsc *ts_dev)
> /* The steps1 … end and bit 0 for TS_Charge */
> stepenable = (1 << (end_step + 2)) - 1;
> ts_dev->step_mask = stepenable;
> - am335x_tsc_se_set(ts_dev->mfd_tscadc, ts_dev->step_mask);
> + am335x_tsc_se_set_cache(ts_dev->mfd_tscadc, ts_dev->step_mask);
> }
>
> static void titsc_read_coordinates(struct titsc *ts_dev,
> @@ -322,7 +322,7 @@ static irqreturn_t titsc_irq(int irq, void *dev)
>
> if (irqclr) {
> titsc_writel(ts_dev, REG_IRQSTATUS, irqclr);
> - am335x_tsc_se_set(ts_dev->mfd_tscadc, ts_dev->step_mask);
> + am335x_tsc_se_set_cache(ts_dev->mfd_tscadc, ts_dev->step_mask);
> return IRQ_HANDLED;
> }
> return IRQ_NONE;
> diff --git a/drivers/mfd/ti_am335x_tscadc.c b/drivers/mfd/ti_am335x_tscadc.c
> index 67d0eb4..cb0c211 100644
> --- a/drivers/mfd/ti_am335x_tscadc.c
> +++ b/drivers/mfd/ti_am335x_tscadc.c
> @@ -53,24 +53,32 @@ static void am335x_tsc_se_update(struct ti_tscadc_dev *tsadc)
> tscadc_writel(tsadc, REG_SE, tsadc->reg_se_cache);
> }
>
> -void am335x_tsc_se_set(struct ti_tscadc_dev *tsadc, u32 val)
> +void am335x_tsc_se_set_cache(struct ti_tscadc_dev *tsadc, u32 val)
> {
> unsigned long flags;
>
> spin_lock_irqsave(&tsadc->reg_lock, flags);
> - tsadc->reg_se_cache = tscadc_readl(tsadc, REG_SE);
> tsadc->reg_se_cache |= val;
> am335x_tsc_se_update(tsadc);
> spin_unlock_irqrestore(&tsadc->reg_lock, flags);
> }
> -EXPORT_SYMBOL_GPL(am335x_tsc_se_set);
> +EXPORT_SYMBOL_GPL(am335x_tsc_se_set_cache);
> +
> +void am335x_tsc_se_set_once(struct ti_tscadc_dev *tsadc, u32 val)
> +{
> + unsigned long flags;
> +
> + spin_lock_irqsave(&tsadc->reg_lock, flags);
> + tscadc_writel(tsadc, REG_SE, tsadc->reg_se_cache | val);
> + spin_unlock_irqrestore(&tsadc->reg_lock, flags);
> +}
> +EXPORT_SYMBOL_GPL(am335x_tsc_se_set_once);
>
> void am335x_tsc_se_clr(struct ti_tscadc_dev *tsadc, u32 val)
> {
> unsigned long flags;
>
> spin_lock_irqsave(&tsadc->reg_lock, flags);
> - tsadc->reg_se_cache = tscadc_readl(tsadc, REG_SE);
> tsadc->reg_se_cache &= ~val;
> am335x_tsc_se_update(tsadc);
> spin_unlock_irqrestore(&tsadc->reg_lock, flags);
> diff --git a/include/linux/mfd/ti_am335x_tscadc.h b/include/linux/mfd/ti_am335x_tscadc.h
> index 1fe7219..2fa9c06 100644
> --- a/include/linux/mfd/ti_am335x_tscadc.h
> +++ b/include/linux/mfd/ti_am335x_tscadc.h
> @@ -176,7 +176,8 @@ static inline struct ti_tscadc_dev *ti_tscadc_dev_get(struct platform_device *p)
> return *tscadc_dev;
> }
>
> -void am335x_tsc_se_set(struct ti_tscadc_dev *tsadc, u32 val);
> +void am335x_tsc_se_set_cache(struct ti_tscadc_dev *tsadc, u32 val);
> +void am335x_tsc_se_set_once(struct ti_tscadc_dev *tsadc, u32 val);
> void am335x_tsc_se_clr(struct ti_tscadc_dev *tsadc, u32 val);
>
> #endif
>
--
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