[PATCH v5 2/6] spmi: apple: Validate FIFO state

[Sasha Finkelstein]

From: Alba Mendez <me at alba.sh>

Check for data before reading the body of a reply, and check for
end of data afterwards.

Signed-off-by: Alba Mendez <me at alba.sh>
Reviewed-by: Janne Grunau <j at jannau.net>
Signed-off-by: Sasha Finkelstein <k at chaosmail.tech>
---
 drivers/spmi/spmi-apple-controller.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/drivers/spmi/spmi-apple-controller.c b/drivers/spmi/spmi-apple-controller.c
index 376cf682c43e..15721cb41d5c 100644
--- a/drivers/spmi/spmi-apple-controller.c
+++ b/drivers/spmi/spmi-apple-controller.c
@@ -21,7 +21,9 @@
 #define SPMI_STATUS_REG 0
 #define SPMI_CMD_REG 0x4
 #define SPMI_RSP_REG 0x8
+#define SPMI_ACT_REG 0xa4
 
+#define SPMI_ACT_FIFO_FLUSH BIT(0)
 #define SPMI_RX_FIFO_EMPTY BIT(24)
 
 #define REG_POLL_INTERVAL_US 10000
@@ -29,6 +31,7 @@
 
 struct apple_spmi {
 	void __iomem *regs;
+	bool prev_fail;
 };
 
 #define poll_reg(spmi, reg, val, cond) \
@@ -49,6 +52,7 @@ static int apple_spmi_wait_rx_not_empty(struct spmi_controller *ctrl)
 
 	ret = poll_reg(spmi, SPMI_STATUS_REG, status, !(status & SPMI_RX_FIFO_EMPTY));
 	if (ret) {
+		spmi->prev_fail = true;
 		dev_err(&ctrl->dev,
 			"failed to wait for RX FIFO not empty\n");
 		return ret;
@@ -67,6 +71,11 @@ static int spmi_read_cmd(struct spmi_controller *ctrl, u8 opc, u8 sid,
 	u8 i;
 	int ret;
 
+	if (spmi->prev_fail) {
+		writel(SPMI_ACT_FIFO_FLUSH, spmi->regs + SPMI_ACT_REG);
+		spmi->prev_fail = false;
+	}
+
 	writel(spmi_cmd, spmi->regs + SPMI_CMD_REG);
 
 	ret = apple_spmi_wait_rx_not_empty(ctrl);
@@ -78,6 +87,12 @@ static int spmi_read_cmd(struct spmi_controller *ctrl, u8 opc, u8 sid,
 
 	/* Read SPMI data reply */
 	while (len_read < len) {
+		if (readl(spmi->regs + SPMI_STATUS_REG) & SPMI_RX_FIFO_EMPTY) {
+			spmi->prev_fail = true;
+			dev_err_ratelimited(&ctrl->dev,
+					    "FIFO lacks reply data, controller stuck?\n");
+			return -EIO;
+		}
 		rsp = readl(spmi->regs + SPMI_RSP_REG);
 		i = 0;
 		while ((len_read < len) && (i < 4)) {
@@ -86,6 +101,11 @@ static int spmi_read_cmd(struct spmi_controller *ctrl, u8 opc, u8 sid,
 		}
 	}
 
+	if (!(readl(spmi->regs + SPMI_STATUS_REG) & SPMI_RX_FIFO_EMPTY)) {
+		dev_warn(&ctrl->dev, "FIFO has extra data\n");
+		spmi->prev_fail = true;
+	}
+
 	return 0;
 }
 
@@ -97,6 +117,11 @@ static int spmi_write_cmd(struct spmi_controller *ctrl, u8 opc, u8 sid,
 	size_t i = 0, j;
 	int ret;
 
+	if (spmi->prev_fail) {
+		writel(SPMI_ACT_FIFO_FLUSH, spmi->regs + SPMI_ACT_REG);
+		spmi->prev_fail = false;
+	}
+
 	writel(spmi_cmd, spmi->regs + SPMI_CMD_REG);
 
 	while (i < len) {
@@ -115,6 +140,11 @@ static int spmi_write_cmd(struct spmi_controller *ctrl, u8 opc, u8 sid,
 	/* Discard */
 	readl(spmi->regs + SPMI_RSP_REG);
 
+	if (!(readl(spmi->regs + SPMI_STATUS_REG) & SPMI_RX_FIFO_EMPTY)) {
+		dev_warn(&ctrl->dev, "FIFO has extra data\n");
+		spmi->prev_fail = true;
+	}
+
 	return 0;
 }
 

-- 
2.55.0