lkml.org 
[lkml]   [2019]   [Jun]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
SubjectRe: [PATCH v2 3/6] serial: uartps: Fix multiple line dereference
From
Date
On Wed, 2019-06-12 at 13:14 +0200, Michal Simek wrote:
> From: Nava kishore Manne <nava.manne@xilinx.com>
>
> Trivial patch which fixes this checkpatch warning:
> WARNING: Avoid multiple line dereference - prefer 'port->state->xmit.tail'
> + port->state->xmit.buf[port->state->xmit.
> + tail], port->membase + CDNS_UART_FIFO);
>
> Fixes: c8dbdc842d30 ("serial: xuartps: Rewrite the interrupt handling logic")
> Signed-off-by: Nava kishore Manne <nava.manne@xilinx.com>
> Signed-off-by: Michal Simek <michal.simek@xilinx.com>
> ---
>
> Changes in v2:
> - Split patch from v1
> - Add Fixes tag
>
> drivers/tty/serial/xilinx_uartps.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c
> index c84db82bdaab..4cd20c036750 100644
> --- a/drivers/tty/serial/xilinx_uartps.c
> +++ b/drivers/tty/serial/xilinx_uartps.c
> @@ -319,8 +319,8 @@ static void cdns_uart_handle_tx(void *dev_id)
> * register.
> */
> writel(
> - port->state->xmit.buf[port->state->xmit.
> - tail], port->membase + CDNS_UART_FIFO);
> + port->state->xmit.buf[port->state->xmit.tail],
> + port->membase + CDNS_UART_FIFO);
>
> port->icount.tx++;

Another way to rewrite this is to use a temporary for
port->state->xmit and also return early on empty to
avoid unnecessary indentation.

Using a temporary can also reduce object size a bit by
removing unnecessary dereferences: (defconfig x86-64)

$ size drivers/tty/serial/xilinx_uartps.o*
text data bss dec hex filename
26578 4632 320 31530 7b2a drivers/tty/serial/xilinx_uartps.o.new
26642 4632 320 31594 7b6a drivers/tty/serial/xilinx_uartps.o.old

i.e.:

---
drivers/tty/serial/xilinx_uartps.c | 54 ++++++++++++++++++--------------------
1 file changed, 25 insertions(+), 29 deletions(-)

diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c
index 605354fd60b1..09b586aeeca3 100644
--- a/drivers/tty/serial/xilinx_uartps.c
+++ b/drivers/tty/serial/xilinx_uartps.c
@@ -305,40 +305,36 @@ static void cdns_uart_handle_rx(void *dev_id, unsigned int isrstatus)
static void cdns_uart_handle_tx(void *dev_id)
{
struct uart_port *port = (struct uart_port *)dev_id;
+ struct circ_buf *xmit = &port->state->xmit;
unsigned int numbytes;

- if (uart_circ_empty(&port->state->xmit)) {
+ if (uart_circ_empty(xmit)) {
writel(CDNS_UART_IXR_TXEMPTY, port->membase + CDNS_UART_IDR);
- } else {
- numbytes = port->fifosize;
- while (numbytes && !uart_circ_empty(&port->state->xmit) &&
- !(readl(port->membase + CDNS_UART_SR) & CDNS_UART_SR_TXFULL)) {
- /*
- * Get the data from the UART circular buffer
- * and write it to the cdns_uart's TX_FIFO
- * register.
- */
- writel(
- port->state->xmit.buf[port->state->xmit.
- tail], port->membase + CDNS_UART_FIFO);
-
- port->icount.tx++;
-
- /*
- * Adjust the tail of the UART buffer and wrap
- * the buffer if it reaches limit.
- */
- port->state->xmit.tail =
- (port->state->xmit.tail + 1) &
- (UART_XMIT_SIZE - 1);
-
- numbytes--;
- }
+ return;
+ }
+
+ numbytes = port->fifosize;
+ while (numbytes && !uart_circ_empty(xmit) &&
+ !(readl(port->membase + CDNS_UART_SR) & CDNS_UART_SR_TXFULL)) {
+ /*
+ * Get the data from the UART circular buffer and write it
+ * to the cdns_uart's TX_FIFO register.
+ */
+ writel(xmit->buf[xmit->tail], port->membase + CDNS_UART_FIFO);
+
+ port->icount.tx++;
+
+ /*
+ * Adjust the tail of the UART buffer and wrap the buffer
+ * if it reaches limit.
+ */
+ xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);

- if (uart_circ_chars_pending(
- &port->state->xmit) < WAKEUP_CHARS)
- uart_write_wakeup(port);
+ numbytes--;
}
+
+ if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
+ uart_write_wakeup(port);
}

/**

\
 
 \ /
  Last update: 2019-06-12 18:57    [W:0.037 / U:92.340 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site