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Commit 0735cfdf authored by Liviu Dudau's avatar Liviu Dudau
Browse files

drm/mali-dp: Improve writeback handling for DP500. 



Mali DP500 operates in continuous writeback mode (writes frame content
until stopped) and it needs special handling in order to behave like
a one-shot writeback engine. The original state machine added for DP500
was a bit fragile, as it did not handle correctly cases where a new
atomic commit was in progress when the SE IRQ happens and it would
commit some partial updates.

Improve the handling by adding a parameter to the set_config_valid()
function to clear the config valid bit in hardware before starting a
new commit and by introducing a MW_RESTART state in the writeback
state machine to cater for the case where a new writeback commit
gets submitted while the last one is still being active.

Reported-by: default avatarBrian Starkey <brian.starkey@arm.com>
Reviewed-by: default avatarBrian Starkey <brian.starkey@arm.com>
Signed-off-by: default avatarLiviu Dudau <liviu.dudau@arm.com>
parent 8cbc5caf

drivers/gpu/drm/arm/malidp_drv.c

+2 −1
Original line number Diff line number Diff line
@@ -171,7 +171,7 @@ static int malidp_set_and_wait_config_valid(struct drm_device *drm) 
	struct malidp_hw_device *hwdev = malidp->dev;

	int ret;



	hwdev->hw->set_config_valid(hwdev);

	hwdev->hw->set_config_valid(hwdev, 1);

	/* don't wait for config_valid flag if we are in config mode */

	if (hwdev->hw->in_config_mode(hwdev)) {

		atomic_set(&malidp->config_valid, MALIDP_CONFIG_VALID_DONE);
@@ -230,6 +230,7 @@ static void malidp_atomic_commit_tail(struct drm_atomic_state *state) 
	 * know that we are updating registers

	 */

	atomic_set(&malidp->config_valid, MALIDP_CONFIG_START);

	malidp->dev->hw->set_config_valid(malidp->dev, 0);



	drm_atomic_helper_commit_modeset_disables(drm, state);

drivers/gpu/drm/arm/malidp_hw.c

+28 −11
Original line number Diff line number Diff line
@@ -27,7 +27,8 @@ enum { 
	MW_NOT_ENABLED = 0,	/* SE writeback not enabled */

	MW_ONESHOT,		/* SE in one-shot mode for writeback */

	MW_START,		/* SE started writeback */

	MW_STOP,		/* SE finished writeback */

	MW_RESTART,		/* SE will start another writeback after this one */

	MW_STOP,		/* SE needs to stop after this writeback */

};



static const struct malidp_format_id malidp500_de_formats[] = {
@@ -231,9 +232,12 @@ static bool malidp500_in_config_mode(struct malidp_hw_device *hwdev) 
	return false;

}



static void malidp500_set_config_valid(struct malidp_hw_device *hwdev)

static void malidp500_set_config_valid(struct malidp_hw_device *hwdev, u8 value)

{

	if (value)

		malidp_hw_setbits(hwdev, MALIDP_CFG_VALID, MALIDP500_CONFIG_VALID);

	else

		malidp_hw_clearbits(hwdev, MALIDP_CFG_VALID, MALIDP500_CONFIG_VALID);

}



static void malidp500_modeset(struct malidp_hw_device *hwdev, struct videomode *mode)
@@ -386,6 +390,10 @@ static int malidp500_enable_memwrite(struct malidp_hw_device *hwdev, 
	/* enable the scaling engine block */

	malidp_hw_setbits(hwdev, MALIDP_SCALE_ENGINE_EN, de_base + MALIDP_DE_DISPLAY_FUNC);



	/* restart the writeback if already enabled */

	if (hwdev->mw_state != MW_NOT_ENABLED)

		hwdev->mw_state = MW_RESTART;

	else

		hwdev->mw_state = MW_START;



	malidp_hw_write(hwdev, fmt_id, base + MALIDP_MW_FORMAT);
@@ -415,7 +423,7 @@ static void malidp500_disable_memwrite(struct malidp_hw_device *hwdev) 
{

	u32 base = malidp_get_block_base(hwdev, MALIDP_DE_BLOCK);



	if (hwdev->mw_state == MW_START)

	if (hwdev->mw_state == MW_START || hwdev->mw_state == MW_RESTART)

		hwdev->mw_state = MW_STOP;

	malidp_hw_clearbits(hwdev, MALIDP_SE_MEMWRITE_EN, MALIDP500_SE_CONTROL);

	malidp_hw_clearbits(hwdev, MALIDP_SCALE_ENGINE_EN, base + MALIDP_DE_DISPLAY_FUNC);
@@ -500,9 +508,12 @@ static bool malidp550_in_config_mode(struct malidp_hw_device *hwdev) 
	return false;

}



static void malidp550_set_config_valid(struct malidp_hw_device *hwdev)

static void malidp550_set_config_valid(struct malidp_hw_device *hwdev, u8 value)

{

	if (value)

		malidp_hw_setbits(hwdev, MALIDP_CFG_VALID, MALIDP550_CONFIG_VALID);

	else

		malidp_hw_clearbits(hwdev, MALIDP_CFG_VALID, MALIDP550_CONFIG_VALID);

}



static void malidp550_modeset(struct malidp_hw_device *hwdev, struct videomode *mode)
@@ -1005,15 +1016,21 @@ static irqreturn_t malidp_se_irq(int irq, void *arg) 
			/* disable writeback after stop */

			hwdev->mw_state = MW_NOT_ENABLED;

			break;

		case MW_RESTART:

			drm_writeback_signal_completion(&malidp->mw_connector, 0);

			/* fall through to a new start */

		case MW_START:

			/* writeback started, need to emulate one-shot mode */

			hw->disable_memwrite(hwdev);

			/*

			 * only set config_valid HW bit if there is no

			 * other update in progress

			 * only set config_valid HW bit if there is no other update

			 * in progress or if we raced ahead of the DE IRQ handler

			 * and config_valid flag will not be update until later

			 */

			if (atomic_read(&malidp->config_valid) != MALIDP_CONFIG_START)

				hw->set_config_valid(hwdev);

			status = malidp_hw_read(hwdev, hw->map.dc_base + MALIDP_REG_STATUS);

			if ((atomic_read(&malidp->config_valid) != MALIDP_CONFIG_START) ||

			    (status & hw->map.dc_irq_map.vsync_irq))

				hw->set_config_valid(hwdev, 1);

			break;

		}

	}

drivers/gpu/drm/arm/malidp_hw.h

+6 −5
Original line number Diff line number Diff line
@@ -152,12 +152,13 @@ struct malidp_hw { 
	bool (*in_config_mode)(struct malidp_hw_device *hwdev);



	/*

	 * Set configuration valid flag for hardware parameters that can

	 * be changed outside the configuration mode. Hardware will use

	 * the new settings when config valid is set after the end of the

	 * current buffer scanout

	 * Set/clear configuration valid flag for hardware parameters that can

	 * be changed outside the configuration mode to the given value.

	 * Hardware will use the new settings when config valid is set,

	 * after the end of the current buffer scanout, and will ignore

	 * any new values for those parameters if config valid flag is cleared

	 */

	void (*set_config_valid)(struct malidp_hw_device *hwdev);

	void (*set_config_valid)(struct malidp_hw_device *hwdev, u8 value);



	/*

	 * Set a new mode in hardware. Requires the hardware to be in