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From:   Yannick FERTRE <yannick.fertre@st.com>
To:     Philippe CORNU <philippe.cornu@st.com>,
        Benjamin GAIGNARD <benjamin.gaignard@st.com>,
        "airlied@linux.ie" <airlied@linux.ie>
CC:     "dri-devel@lists.freedesktop.org" <dri-devel@lists.freedesktop.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] drm: stm: implement get_scanout_position function
Thread-Topic: [PATCH] drm: stm: implement get_scanout_position function
Thread-Index: AQHUD6lh/FtQB5XoQ0G3N1zp/AXzb6R9OioAgIb5igCAADbZgA==
Date:   Thu, 27 Sep 2018 11:32:00 +0000
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Reviewed-by: Yannick Fertr? <yannick.fertre@st.com>
Tested-by: Yannick Fertr? <yannick.fertre@st.com>

On 09/27/2018 10:15 AM, Yannick FERTRE wrote:
> Reviewed-by/tested-by: yannick.fertre@st.com
>
> -------- Forwarded Message --------
> Subject: [PATCH] drm: stm: implement get_scanout_position function
> Date: Fri, 29 Jun 2018 15:01:40 +0200
> From: Benjamin Gaignard <benjamin.gaignard@linaro.org>
> To: yannick.fertre@st.com, philippe.cornu@st.com, airlied@linux.ie
> CC: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
> Benjamin Gaignard <benjamin.gaignard@linaro.org>, Benjamin Gaignard
> <benjamin.gaignard@st.com>
>
> Hardware allow to read the position in scanout buffer so
> we can use this information to make wait of vblank more accurate.
>
> Active area bounds (start, end, total height) have already been
> computed and written in ltdc registers, read them and get the
> current line position to compute vpos value.
>
> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
> ---
> ? drivers/gpu/drm/stm/drv.c? |? 2 ++
> ? drivers/gpu/drm/stm/ltdc.c | 45
> +++++++++++++++++++++++++++++++++++++++++++++
> ? drivers/gpu/drm/stm/ltdc.h |? 5 +++++
> ? 3 files changed, 52 insertions(+)
>
> diff --git a/drivers/gpu/drm/stm/drv.c b/drivers/gpu/drm/stm/drv.c
> index 8698e08313e1..ac53383350e3 100644
> --- a/drivers/gpu/drm/stm/drv.c
> +++ b/drivers/gpu/drm/stm/drv.c
> @@ -72,6 +72,8 @@ static struct drm_driver drv_driver = {
> ????? .gem_prime_vmap = drm_gem_cma_prime_vmap,
> ????? .gem_prime_vunmap = drm_gem_cma_prime_vunmap,
> ????? .gem_prime_mmap = drm_gem_cma_prime_mmap,
> +??? .get_scanout_position = ltdc_crtc_scanoutpos,
> +??? .get_vblank_timestamp = drm_calc_vbltimestamp_from_scanoutpos,
> ? };
> ?? static int drv_load(struct drm_device *ddev)
> diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
> index d997a6014d6c..05b714673042 100644
> --- a/drivers/gpu/drm/stm/ltdc.c
> +++ b/drivers/gpu/drm/stm/ltdc.c
> @@ -148,6 +148,8 @@
> ? #define IER_TERRIE??? BIT(2)??????? /* Transfer ERRor Interrupt 
> Enable */
> ? #define IER_RRIE??? BIT(3)??????? /* Register Reload Interrupt 
> enable */
> ? +#define CPSR_CYPOS??? GENMASK(15, 0)??? /* Current Y position */
> +
> ? #define ISR_LIF??????? BIT(0)??????? /* Line Interrupt Flag */
> ? #define ISR_FUIF??? BIT(1)??????? /* Fifo Underrun Interrupt Flag */
> ? #define ISR_TERRIF??? BIT(2)??????? /* Transfer ERRor Interrupt Flag */
> @@ -622,6 +624,49 @@ static void ltdc_crtc_disable_vblank(struct
> drm_crtc *crtc)
> ????? reg_clear(ldev->regs, LTDC_IER, IER_LIE);
> ? }
> ? +bool ltdc_crtc_scanoutpos(struct drm_device *ddev, unsigned int pipe,
> +????????????? bool in_vblank_irq, int *vpos, int *hpos,
> +????????????? ktime_t *stime, ktime_t *etime,
> +????????????? const struct drm_display_mode *mode)
> +{
> +??? struct ltdc_device *ldev = ddev->dev_private;
> +??? int line, vactive_start, vactive_end, vtotal;
> +
> +??? if (stime)
> +??????? *stime = ktime_get();
> +
> +??? /* The active area starts after vsync + front porch and ends
> +???? * at vsync + front porc + display size.
> +???? * The total height also include back porch.
> +???? * We have 3 possible cases to handle:
> +???? * - line < vactive_start: vpos = line - vactive_start and will be
> +???? * negative
> +???? * - vactive_start < line < vactive_end: vpos = line - vactive_start
> +???? * and will be positive
> +???? * - line > vactive_end: vpos = line - vtotal - vactive_start
> +???? * and will negative
> +???? *
> +???? * Computation for the two first cases are identical so we can
> +???? * simplify the code and only test if line > vactive_end
> +???? */
> +??? line = reg_read(ldev->regs, LTDC_CPSR) & CPSR_CYPOS;
> +??? vactive_start = reg_read(ldev->regs, LTDC_BPCR) & BPCR_AVBP;
> +??? vactive_end = reg_read(ldev->regs, LTDC_AWCR) & AWCR_AAH;
> +??? vtotal = reg_read(ldev->regs, LTDC_TWCR) & TWCR_TOTALH;
> +
> +??? if (line > vactive_end)
> +??????? *vpos = line - vtotal - vactive_start;
> +??? else
> +??????? *vpos = line - vactive_start;
> +
> +??? *hpos = 0;
> +
> +??? if (etime)
> +??????? *etime = ktime_get();
> +
> +??? return true;
> +}
> +
> ? static const struct drm_crtc_funcs ltdc_crtc_funcs = {
> ????? .destroy = drm_crtc_cleanup,
> ????? .set_config = drm_atomic_helper_set_config,
> diff --git a/drivers/gpu/drm/stm/ltdc.h b/drivers/gpu/drm/stm/ltdc.h
> index 1e16d6afb0d2..b8c5cc41e17a 100644
> --- a/drivers/gpu/drm/stm/ltdc.h
> +++ b/drivers/gpu/drm/stm/ltdc.h
> @@ -37,6 +37,11 @@ struct ltdc_device {
> ????? struct fps_info plane_fpsi[LTDC_MAX_LAYER];
> ? };
> ? +bool ltdc_crtc_scanoutpos(struct drm_device *dev, unsigned int pipe,
> +????????????? bool in_vblank_irq, int *vpos, int *hpos,
> +????????????? ktime_t *stime, ktime_t *etime,
> +????????????? const struct drm_display_mode *mode);
> +
> ? int ltdc_load(struct drm_device *ddev);
> ? void ltdc_unload(struct drm_device *ddev);
> ? -- 2.15.0
>

-- 
Yannick Fertr? | TINA: 166 7152 | Tel: +33 244027152 | Mobile: +33 620600270
Microcontrollers and Digital ICs Group | Microcontrolleurs Division