[PATCH] soc: imx: imx8m-blk-ctrl: set LCDIF panic read hurry level

[Lucas Stach]

When the LCDIF block signals a panic condition due to the display FIFO
falling below the threshold, the priority at the NoC level is boosted
to the value set in the LCDIF_ARCACHE_CTRL register of i.MX8MP mediamix
blk-ctrl. Same as all other blk-ctrl registers this register is reset
when the domain is powered down. Initialize the panic hurry levels for
both LCIF interfaces to the maximium priority (same as downstream TF-A
and proven to work with the other priorities set in the interconnect
driver) when coming back from power down.

Signed-off-by: Lucas Stach <l.stach at pengutronix.de>
---
 drivers/soc/imx/imx8m-blk-ctrl.c | 27 +++++++++++++++++++++------
 1 file changed, 21 insertions(+), 6 deletions(-)

diff --git a/drivers/soc/imx/imx8m-blk-ctrl.c b/drivers/soc/imx/imx8m-blk-ctrl.c
index 00879615a701..b93b296c47be 100644
--- a/drivers/soc/imx/imx8m-blk-ctrl.c
+++ b/drivers/soc/imx/imx8m-blk-ctrl.c
@@ -4,6 +4,7 @@
  * Copyright 2021 Pengutronix, Lucas Stach <kernel at pengutronix.de>
  */
 
+#include <linux/bitfield.h>
 #include <linux/device.h>
 #include <linux/interconnect.h>
 #include <linux/module.h>
@@ -649,6 +650,10 @@ static const struct imx8m_blk_ctrl_data imx8mn_disp_blk_ctl_dev_data = {
 	.num_domains = ARRAY_SIZE(imx8mn_disp_blk_ctl_domain_data),
 };
 
+#define LCDIF_ARCACHE_CTRL	0x4c
+#define  LCDIF_1_RD_HURRY	GENMASK(15, 13)
+#define  LCDIF_0_RD_HURRY	GENMASK(12, 10)
+
 static int imx8mp_media_power_notifier(struct notifier_block *nb,
 				unsigned long action, void *data)
 {
@@ -662,14 +667,24 @@ static int imx8mp_media_power_notifier(struct notifier_block *nb,
 	regmap_set_bits(bc->regmap, BLK_CLK_EN, BIT(8));
 	regmap_set_bits(bc->regmap, BLK_SFT_RSTN, BIT(8));
 
-	/*
-	 * On power up we have no software backchannel to the GPC to
-	 * wait for the ADB handshake to happen, so we just delay for a
-	 * bit. On power down the GPC driver waits for the handshake.
-	 */
-	if (action == GENPD_NOTIFY_ON)
+	if (action == GENPD_NOTIFY_ON) {
+		/*
+		 * On power up we have no software backchannel to the GPC to
+		 * wait for the ADB handshake to happen, so we just delay for a
+		 * bit. On power down the GPC driver waits for the handshake.
+		 */
 		udelay(5);
 
+		/*
+		 * Set panic read hurry level for both LCDIF interfaces to
+		 * maximum priority to minimize chances of display FIFO
+		 * underflow.
+		 */
+		regmap_set_bits(bc->regmap, LCDIF_ARCACHE_CTRL,
+				FIELD_PREP(LCDIF_1_RD_HURRY, 7) |
+				FIELD_PREP(LCDIF_0_RD_HURRY, 7));
+	}
+
 	return NOTIFY_OK;
 }
 
-- 
2.30.2