[PATCH] gpu: ipu-v3: pre: implement workaround for ERR009624

[Philipp Zabel]

From: Lucas Stach <l.stach at pengutronix.de>

The PRE has a bug where a software write to the CTRL register can block
the setting of the ENABLE bit by the hardware in auto repeat mode. When
this happens the PRE will fail to handle new jobs. To work around this
software must not write to CTRL register when the PRE store engine is
inside the unsafe window, where a hardware update to the ENABLE bit
may happen.

Signed-off-by: Lucas Stach <l.stach at pengutronix.de>
[p.zabel at pengutronix.de: rebased before PRE tiled prefetch support]
Signed-off-by: Philipp Zabel <p.zabel at pengutronix.de>
---
 drivers/gpu/ipu-v3/ipu-pre.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/drivers/gpu/ipu-v3/ipu-pre.c b/drivers/gpu/ipu-v3/ipu-pre.c
index c35f74c830657..c860a7997cb59 100644
--- a/drivers/gpu/ipu-v3/ipu-pre.c
+++ b/drivers/gpu/ipu-v3/ipu-pre.c
@@ -73,6 +73,14 @@
 #define  IPU_PRE_STORE_ENG_CTRL_WR_NUM_BYTES(v)		((v & 0x7) << 1)
 #define  IPU_PRE_STORE_ENG_CTRL_OUTPUT_ACTIVE_BPP(v)	((v & 0x3) << 4)
 
+#define IPU_PRE_STORE_ENG_STATUS			0x120
+#define  IPU_PRE_STORE_ENG_STATUS_STORE_BLOCK_X_MASK	0xffff
+#define  IPU_PRE_STORE_ENG_STATUS_STORE_BLOCK_X_SHIFT	0
+#define  IPU_PRE_STORE_ENG_STATUS_STORE_BLOCK_Y_MASK	0x3fff
+#define  IPU_PRE_STORE_ENG_STATUS_STORE_BLOCK_Y_SHIFT	16
+#define  IPU_PRE_STORE_ENG_STATUS_STORE_FIFO_FULL	(1 << 30)
+#define  IPU_PRE_STORE_ENG_STATUS_STORE_FIELD		(1 << 31)
+
 #define IPU_PRE_STORE_ENG_SIZE				0x130
 #define  IPU_PRE_STORE_ENG_SIZE_INPUT_WIDTH(v)		((v & 0xffff) << 0)
 #define  IPU_PRE_STORE_ENG_SIZE_INPUT_HEIGHT(v)		((v & 0xffff) << 16)
@@ -93,6 +101,7 @@ struct ipu_pre {
 	dma_addr_t		buffer_paddr;
 	void			*buffer_virt;
 	bool			in_use;
+	unsigned int		safe_window_end;
 };
 
 static DEFINE_MUTEX(ipu_pre_list_mutex);
@@ -160,6 +169,9 @@ void ipu_pre_configure(struct ipu_pre *pre, unsigned int width,
 	u32 active_bpp = info->cpp[0] >> 1;
 	u32 val;
 
+	/* calculate safe window for ctrl register updates */
+	pre->safe_window_end = height - 2;
+
 	writel(bufaddr, pre->regs + IPU_PRE_CUR_BUF);
 	writel(bufaddr, pre->regs + IPU_PRE_NEXT_BUF);
 
@@ -199,7 +211,24 @@ void ipu_pre_configure(struct ipu_pre *pre, unsigned int width,
 
 void ipu_pre_update(struct ipu_pre *pre, unsigned int bufaddr)
 {
+	unsigned long timeout = jiffies + msecs_to_jiffies(5);
+	unsigned short current_yblock;
+	u32 val;
+
 	writel(bufaddr, pre->regs + IPU_PRE_NEXT_BUF);
+
+	do {
+		if (time_after(jiffies, timeout)) {
+			dev_warn(pre->dev, "timeout waiting for PRE safe window\n");
+			return;
+		}
+
+		val = readl(pre->regs + IPU_PRE_STORE_ENG_STATUS);
+		current_yblock =
+			(val >> IPU_PRE_STORE_ENG_STATUS_STORE_BLOCK_Y_SHIFT) &
+			IPU_PRE_STORE_ENG_STATUS_STORE_BLOCK_Y_MASK;
+	} while (current_yblock == 0 || current_yblock >= pre->safe_window_end);
+
 	writel(IPU_PRE_CTRL_SDW_UPDATE, pre->regs + IPU_PRE_CTRL_SET);
 }
 
-- 
2.11.0