[PATCH 6.6 22/25] spi: cadence-quadspi: Implement refcount to handle unbind during busy

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

6.6-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Khairul Anuar Romli <khairul.anuar.romli@altera.com>

commit 7446284023e8ef694fb392348185349c773eefb3 upstream.

driver support indirect read and indirect write operation with
assumption no force device removal(unbind) operation. However
force device removal(removal) is still available to root superuser.

Unbinding driver during operation causes kernel crash. This changes
ensure driver able to handle such operation for indirect read and
indirect write by implementing refcount to track attached devices
to the controller and gracefully wait and until attached devices
remove operation completed before proceed with removal operation.

Signed-off-by: Khairul Anuar Romli <khairul.anuar.romli@altera.com>
Reviewed-by: Matthew Gerlach <matthew.gerlach@altera.com>
Reviewed-by: Niravkumar L Rabara <nirav.rabara@altera.com>
Link: https://patch.msgid.link/8704fd6bd2ff4d37bba4a0eacf5eba3ba001079e.1756168074.git.khairul.anuar.romli@altera.com
Signed-off-by: Mark Brown <broonie@kernel.org>
[Add cqspi defination in cqspi_exec_mem_op and minor context change fixed.]
Signed-off-by: Robert Garcia <rob_garcia@163.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/spi/spi-cadence-quadspi.c |   34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

--- a/drivers/spi/spi-cadence-quadspi.c
+++ b/drivers/spi/spi-cadence-quadspi.c
@@ -100,6 +100,8 @@ struct cqspi_st {
 	bool			apb_ahb_hazard;
 
 	bool			is_jh7110; /* Flag for StarFive JH7110 SoC */
+	refcount_t		refcount;
+	refcount_t		inflight_ops;
 };
 
 struct cqspi_driver_platdata {
@@ -705,6 +707,9 @@ static int cqspi_indirect_read_execute(s
 	u8 *rxbuf_end = rxbuf + n_rx;
 	int ret = 0;
 
+	if (!refcount_read(&cqspi->refcount))
+		return -ENODEV;
+
 	writel(from_addr, reg_base + CQSPI_REG_INDIRECTRDSTARTADDR);
 	writel(remaining, reg_base + CQSPI_REG_INDIRECTRDBYTES);
 
@@ -1021,6 +1026,9 @@ static int cqspi_indirect_write_execute(
 	unsigned int write_bytes;
 	int ret;
 
+	if (!refcount_read(&cqspi->refcount))
+		return -ENODEV;
+
 	writel(to_addr, reg_base + CQSPI_REG_INDIRECTWRSTARTADDR);
 	writel(remaining, reg_base + CQSPI_REG_INDIRECTWRBYTES);
 
@@ -1412,11 +1420,29 @@ static int cqspi_mem_process(struct spi_
 static int cqspi_exec_mem_op(struct spi_mem *mem, const struct spi_mem_op *op)
 {
 	int ret;
+	struct cqspi_st *cqspi = spi_controller_get_devdata(mem->spi->controller);
+
+	if (refcount_read(&cqspi->inflight_ops) == 0)
+		return -ENODEV;
+
+	if (!refcount_read(&cqspi->refcount))
+		return -EBUSY;
+
+	refcount_inc(&cqspi->inflight_ops);
+
+	if (!refcount_read(&cqspi->refcount)) {
+		if (refcount_read(&cqspi->inflight_ops))
+			refcount_dec(&cqspi->inflight_ops);
+		return -EBUSY;
+	}
 
 	ret = cqspi_mem_process(mem, op);
 	if (ret)
 		dev_err(&mem->spi->dev, "operation failed with %d\n", ret);
 
+	if (refcount_read(&cqspi->inflight_ops) > 1)
+		refcount_dec(&cqspi->inflight_ops);
+
 	return ret;
 }
 
@@ -1847,6 +1873,9 @@ static int cqspi_probe(struct platform_d
 		}
 	}
 
+	refcount_set(&cqspi->refcount, 1);
+	refcount_set(&cqspi->inflight_ops, 1);
+
 	ret = devm_request_irq(dev, irq, cqspi_irq_handler, 0,
 			       pdev->name, cqspi);
 	if (ret) {
@@ -1899,6 +1928,11 @@ static void cqspi_remove(struct platform
 {
 	struct cqspi_st *cqspi = platform_get_drvdata(pdev);
 
+	refcount_set(&cqspi->refcount, 0);
+
+	if (!refcount_dec_and_test(&cqspi->inflight_ops))
+		cqspi_wait_idle(cqspi);
+
 	spi_unregister_controller(cqspi->host);
 	cqspi_controller_enable(cqspi, 0);