linux-kernel - [PATCH v2] serial: amba-pl011: do not request memory region twice

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Date:   Mon, 29 Nov 2021 18:42:38 +0100
From:   Lino Sanfilippo <LinoSanfilippo@....de>
To:     gregkh@...uxfoundation.org
Cc:     linux@...linux.org.uk, jirislaby@...nel.org,
        andre.przywara@....com, p.rosenberger@...bus.com, lukas@...ner.de,
        linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
        Lino Sanfilippo <LinoSanfilippo@....de>
Subject: [PATCH v2] serial: amba-pl011: do not request memory region twice

With commit 3873e2d7f63a ("drivers: PL011: refactor pl011_probe()") the
function devm_ioremap() called from pl011_setup_port() was replaced with
devm_ioremap_resource(). Since this function not only remaps but also
requests the ports io memory region it now collides with the .config_port()
callback which requests the same region at uart port registration.

Since devm_ioremap_resource() already claims the memory successfully, the
request in .config_port() fails.

Later at uart port deregistration the attempt to release the unclaimed
memory also fails. The failure results in a “Trying to free nonexistent
resource" warning.

Fix these issues by removing the callbacks that implement the redundant
memory allocation/release. Also make sure that changing the drivers io
memory base address via TIOCSSERIAL is not allowed any more.

Fixes: 3873e2d7f63a ("drivers: PL011: refactor pl011_probe()")
Signed-off-by: Lino Sanfilippo <LinoSanfilippo@....de>
---

Changes in v2:
- add fixes tag (as suggested by Greg)
- adjust pl011_verify_port to avoid changing the mmio address via
  TIOCSSERIAL (as requested by Russel)
- rephrase the commit message


 drivers/tty/serial/amba-pl011.c | 27 +++------------------------
 1 file changed, 3 insertions(+), 24 deletions(-)

diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index d361cd84ff8c..e0e41ce8bb1f 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -2183,32 +2183,13 @@ static const char *pl011_type(struct uart_port *port)
 	return uap->port.type == PORT_AMBA ? uap->type : NULL;
 }
 
-/*
- * Release the memory region(s) being used by 'port'
- */
-static void pl011_release_port(struct uart_port *port)
-{
-	release_mem_region(port->mapbase, SZ_4K);
-}
-
-/*
- * Request the memory region(s) being used by 'port'
- */
-static int pl011_request_port(struct uart_port *port)
-{
-	return request_mem_region(port->mapbase, SZ_4K, "uart-pl011")
-			!= NULL ? 0 : -EBUSY;
-}
-
 /*
  * Configure/autoconfigure the port.
  */
 static void pl011_config_port(struct uart_port *port, int flags)
 {
-	if (flags & UART_CONFIG_TYPE) {
+	if (flags & UART_CONFIG_TYPE)
 		port->type = PORT_AMBA;
-		pl011_request_port(port);
-	}
 }
 
 /*
@@ -2223,6 +2204,8 @@ static int pl011_verify_port(struct uart_port *port, struct serial_struct *ser)
 		ret = -EINVAL;
 	if (ser->baud_base < 9600)
 		ret = -EINVAL;
+	if (port->mapbase != (unsigned long) ser->iomem_base)
+		ret = -EINVAL;
 	return ret;
 }
 
@@ -2275,8 +2258,6 @@ static const struct uart_ops amba_pl011_pops = {
 	.flush_buffer	= pl011_dma_flush_buffer,
 	.set_termios	= pl011_set_termios,
 	.type		= pl011_type,
-	.release_port	= pl011_release_port,
-	.request_port	= pl011_request_port,
 	.config_port	= pl011_config_port,
 	.verify_port	= pl011_verify_port,
 #ifdef CONFIG_CONSOLE_POLL
@@ -2306,8 +2287,6 @@ static const struct uart_ops sbsa_uart_pops = {
 	.shutdown	= sbsa_uart_shutdown,
 	.set_termios	= sbsa_uart_set_termios,
 	.type		= pl011_type,
-	.release_port	= pl011_release_port,
-	.request_port	= pl011_request_port,
 	.config_port	= pl011_config_port,
 	.verify_port	= pl011_verify_port,
 #ifdef CONFIG_CONSOLE_POLL

base-commit: d58071a8a76d779eedab38033ae4c821c30295a5
-- 
2.33.1