[PATCH v14 2/5] media: renesas: vsp1: Add support to deassert/assert reset line

[Biju Das <biju.das.jz@xxxxxxxxxxxxxx>]

As the resets DT property is mandatory, and is present in all .dtsi
in mainline, add support to perform deassert/assert using reference
counted reset handle.

Signed-off-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
Reviewed-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Reviewed-by: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>
Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
---
v13->v14:
 * Added Rb tag from Philipp and Laurent.
 * Updated comment flow.
 * Changed unconditional delay-> conditional delay for register access
   after deassert only for Gen2 SoCs.
 Note:
   There is no such delay required for accessing VI6_IP_VERSION register
   (0x3f00). But accessing registers like VI6_STATUS(0x38) needs some delay
    after deassert. 
v12->v13:
 * Removed unused iopoll.h header file.
 * Added Rb tag from Geert.
v11->v12:
 * Replaced read_poll_timeout_atomic-> udelay(1) as testing on RZ/G1N
   shows this delay is sufficient to avoid lock-up.
 * Removed Rb tags.
v10->v11:
 * To avoid lock-up on R-Car Gen2, added poll for reset status after deassert.
v9->v10:
 * Moved {deassert,assert} calls to vsp1_pm_runtime_{resume,suspend}
v8->v9:
 * No change
v7->v8:
 * No Change
v6->v7:
 * No change
v5->v6:
 * Rebased to media_staging and updated commit header
 * Added Rb tag from Laurent
 * Added forward declaration for struct reset_control
 * Updated vsp1_device_get() with changes suggested by Laurent
 * Updated error message for reset_control_get form ctrl->control.
v4->v5:
 * Added Rb tag from Geert
v3->v4:
 * Restored error check for pm_runtime_resume_and_get and calls
   assert() in case of failure.
v2->v3:
 * Added Rb tag from Philipp
 * If reset_control_deassert() failed, return ret directly. 
v1->v2:
 * Used reference counted reset handle to perform deassert/assert
RFC->v1:
 * Added reset support as separate patch
 * Moved rstc just after the bus_master field in struct vsp1_device
RFC:
 * https://patchwork.kernel.org/project/linux-renesas-soc/patch/20220112174612.10773-21-biju.das.jz@xxxxxxxxxxxxxx/
---
 drivers/media/platform/renesas/vsp1/vsp1.h    |  2 ++
 .../media/platform/renesas/vsp1/vsp1_drv.c    | 29 +++++++++++++++++--
 2 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/drivers/media/platform/renesas/vsp1/vsp1.h b/drivers/media/platform/renesas/vsp1/vsp1.h
index 37cf33c7e6ca..baf898d577ec 100644
--- a/drivers/media/platform/renesas/vsp1/vsp1.h
+++ b/drivers/media/platform/renesas/vsp1/vsp1.h
@@ -22,6 +22,7 @@
 struct clk;
 struct device;
 struct rcar_fcp_device;
+struct reset_control;
 
 struct vsp1_drm;
 struct vsp1_entity;
@@ -79,6 +80,7 @@ struct vsp1_device {
 	void __iomem *mmio;
 	struct rcar_fcp_device *fcp;
 	struct device *bus_master;
+	struct reset_control *rstc;
 
 	struct vsp1_brx *brs;
 	struct vsp1_brx *bru;
diff --git a/drivers/media/platform/renesas/vsp1/vsp1_drv.c b/drivers/media/platform/renesas/vsp1/vsp1_drv.c
index 1f73c48eb738..ef4bcf860923 100644
--- a/drivers/media/platform/renesas/vsp1/vsp1_drv.c
+++ b/drivers/media/platform/renesas/vsp1/vsp1_drv.c
@@ -16,6 +16,7 @@
 #include <linux/of_device.h>
 #include <linux/platform_device.h>
 #include <linux/pm_runtime.h>
+#include <linux/reset.h>
 #include <linux/videodev2.h>
 
 #include <media/rcar-fcp.h>
@@ -622,6 +623,7 @@ static int __maybe_unused vsp1_pm_runtime_suspend(struct device *dev)
 	struct vsp1_device *vsp1 = dev_get_drvdata(dev);
 
 	rcar_fcp_disable(vsp1->fcp);
+	reset_control_assert(vsp1->rstc);
 
 	return 0;
 }
@@ -631,13 +633,31 @@ static int __maybe_unused vsp1_pm_runtime_resume(struct device *dev)
 	struct vsp1_device *vsp1 = dev_get_drvdata(dev);
 	int ret;
 
+	ret = reset_control_deassert(vsp1->rstc);
+	if (ret < 0)
+		return ret;
+
 	if (vsp1->info) {
+		/*
+		 * On R-Car Gen2 and RZ/G1, vsp1 register access after deassert
+		 * can cause lock-up. It is a special case and needs some delay
+		 * to avoid this lock-up.
+		 */
+		if (vsp1->info->gen == 2)
+			udelay(1);
+
 		ret = vsp1_device_init(vsp1);
 		if (ret < 0)
-			return ret;
+			goto done;
 	}
 
-	return rcar_fcp_enable(vsp1->fcp);
+	ret = rcar_fcp_enable(vsp1->fcp);
+
+done:
+	if (ret < 0)
+		reset_control_assert(vsp1->rstc);
+
+	return ret;
 }
 
 static const struct dev_pm_ops vsp1_pm_ops = {
@@ -825,6 +845,11 @@ static int vsp1_probe(struct platform_device *pdev)
 	if (irq < 0)
 		return irq;
 
+	vsp1->rstc = devm_reset_control_get_shared(&pdev->dev, NULL);
+	if (IS_ERR(vsp1->rstc))
+		return dev_err_probe(&pdev->dev, PTR_ERR(vsp1->rstc),
+				     "failed to get reset control\n");
+
 	/* FCP (optional). */
 	fcp_node = of_parse_phandle(pdev->dev.of_node, "renesas,fcp", 0);
 	if (fcp_node) {
-- 
2.25.1