On 2020-03-09 20:52, Laurent Pinchart wrote:
> The driver attempts agressive power management by enabling and disabling
> the AXI clock around register accesses. This results in attempts to
> enable and disable the clock in the IRQ handler, which is a no-go as
> preparing or unpreparing the clock may sleep.
>
> On the other hand, the driver enables the AXI clock when enabling the
> CRTC and keeps it enabled until the CRTC is disabled. This is correct,
> and renders the power management attempt pointless, as interrupts are
> not supposed to occur when the CRTC is off.
>
> The same reasoning can be applied to the CRTC .enable_vblank() and
> .disable_vblank() that are not supposed to be called when the CRTC off
> and thus don't require manual handling of the AXI clock. Furthermore,
> vblank handling is never enabled, which results in the vblank enable and
> disable handlers never being called.
>
> To fix this, remove the manual clock handling in the IRQ, the CRTC
> .enable_vblank() and .disable_vblank() handlers and the plane
> .atomic_update() handler. We however need to handle the clock manually
> in mxsfb_irq_disable() as is calls .disable_vblank() manually and is
> used both at probe and remove time.
>
> The clock disabling is also moved to the last step of the
> mxsfb_crtc_atomic_disable() function, to prepare for enabling vblank
> handling.
>
> Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
Looks good to me!
Reviewed-by: Stefan Agner <stefan@xxxxxxxx>
> ---
> drivers/gpu/drm/mxsfb/mxsfb_drv.c | 6 ++----
> drivers/gpu/drm/mxsfb/mxsfb_kms.c | 15 ++++-----------
> 2 files changed, 6 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> index a8da92976d13..e324bd2a63a5 100644
> --- a/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> +++ b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> @@ -231,7 +231,9 @@ static void mxsfb_irq_disable(struct drm_device *drm)
> {
> struct mxsfb_drm_private *mxsfb = drm->dev_private;
>
> + mxsfb_enable_axi_clk(mxsfb);
> mxsfb->crtc.funcs->disable_vblank(&mxsfb->crtc);
> + mxsfb_disable_axi_clk(mxsfb);
> }
>
> static irqreturn_t mxsfb_irq_handler(int irq, void *data)
> @@ -240,8 +242,6 @@ static irqreturn_t mxsfb_irq_handler(int irq, void *data)
> struct mxsfb_drm_private *mxsfb = drm->dev_private;
> u32 reg;
>
> - mxsfb_enable_axi_clk(mxsfb);
> -
> reg = readl(mxsfb->base + LCDC_CTRL1);
>
> if (reg & CTRL1_CUR_FRAME_DONE_IRQ)
> @@ -249,8 +249,6 @@ static irqreturn_t mxsfb_irq_handler(int irq, void *data)
>
> writel(CTRL1_CUR_FRAME_DONE_IRQ, mxsfb->base + LCDC_CTRL1 + REG_CLR);
>
> - mxsfb_disable_axi_clk(mxsfb);
> -
> return IRQ_HANDLED;
> }
>
> diff --git a/drivers/gpu/drm/mxsfb/mxsfb_kms.c
> b/drivers/gpu/drm/mxsfb/mxsfb_kms.c
> index ebe0785694cb..ac2696c8483d 100644
> --- a/drivers/gpu/drm/mxsfb/mxsfb_kms.c
> +++ b/drivers/gpu/drm/mxsfb/mxsfb_kms.c
> @@ -344,9 +344,6 @@ static void mxsfb_crtc_atomic_disable(struct drm_crtc *crtc,
> struct drm_pending_vblank_event *event;
>
> mxsfb_disable_controller(mxsfb);
> - mxsfb_disable_axi_clk(mxsfb);
> -
> - pm_runtime_put_sync(drm->dev);
>
> spin_lock_irq(&drm->event_lock);
> event = crtc->state->event;
> @@ -355,6 +352,9 @@ static void mxsfb_crtc_atomic_disable(struct drm_crtc *crtc,
> drm_crtc_send_vblank_event(crtc, event);
> }
> spin_unlock_irq(&drm->event_lock);
> +
> + mxsfb_disable_axi_clk(mxsfb);
> + pm_runtime_put_sync(drm->dev);
> }
>
> static int mxsfb_crtc_enable_vblank(struct drm_crtc *crtc)
> @@ -362,10 +362,8 @@ static int mxsfb_crtc_enable_vblank(struct drm_crtc *crtc)
> struct mxsfb_drm_private *mxsfb = to_mxsfb_drm_private(crtc->dev);
>
> /* Clear and enable VBLANK IRQ */
> - mxsfb_enable_axi_clk(mxsfb);
> writel(CTRL1_CUR_FRAME_DONE_IRQ, mxsfb->base + LCDC_CTRL1 + REG_CLR);
> writel(CTRL1_CUR_FRAME_DONE_IRQ_EN, mxsfb->base + LCDC_CTRL1 + REG_SET);
> - mxsfb_disable_axi_clk(mxsfb);
>
> return 0;
> }
> @@ -375,10 +373,8 @@ static void mxsfb_crtc_disable_vblank(struct
> drm_crtc *crtc)
> struct mxsfb_drm_private *mxsfb = to_mxsfb_drm_private(crtc->dev);
>
> /* Disable and clear VBLANK IRQ */
> - mxsfb_enable_axi_clk(mxsfb);
> writel(CTRL1_CUR_FRAME_DONE_IRQ_EN, mxsfb->base + LCDC_CTRL1 + REG_CLR);
> writel(CTRL1_CUR_FRAME_DONE_IRQ, mxsfb->base + LCDC_CTRL1 + REG_CLR);
> - mxsfb_disable_axi_clk(mxsfb);
> }
>
> static const struct drm_crtc_helper_funcs mxsfb_crtc_helper_funcs = {
> @@ -433,11 +429,8 @@ static void mxsfb_plane_atomic_update(struct
> drm_plane *plane,
> dma_addr_t paddr;
>
> paddr = mxsfb_get_fb_paddr(mxsfb);
> - if (paddr) {
> - mxsfb_enable_axi_clk(mxsfb);
> + if (paddr)
> writel(paddr, mxsfb->base + mxsfb->devdata->next_buf);
> - mxsfb_disable_axi_clk(mxsfb);
> - }
> }
>
> static const struct drm_plane_helper_funcs mxsfb_plane_helper_funcs = {
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