tty: serial: samsung: shrink the clock selection to 8 clocks

<linux/serial_s3c.h> provides a clock selection pool of maximum 4 clocks.
Update the driver to consider a pool selection of maximum 8 clocks.
u8 is large enough to allow more clocks than are supported by the driver
now, and not too big to cause spanning of ``struct s3c24xx_uart_info``
through 2 cachelines when compiled for arm64. The goal is to reduce the
memory footprint of ``struct s3c24xx_uart_info``.
Reviewed-by: Sam Protsenko <semen.protsenko@linaro.org>
Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>
Link: https://lore.kernel.org/r/20240119104526.1221243-18-tudor.ambarus@linaro.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/samsung_tty.c

@@ -81,11 +81,11 @@ struct s3c24xx_uart_info {
 	unsigned long		tx_fifomask;
 	unsigned long		tx_fifoshift;
 	unsigned long		tx_fifofull;
-	unsigned int		def_clk_sel;
-	unsigned long		num_clks;
 	unsigned long		clksel_mask;
 	unsigned long		clksel_shift;
 	unsigned long		ucon_mask;
+	u8			def_clk_sel;
+	u8			num_clks;
 	u8			iotype;
 
 	/* uart port features */
@@ -1340,7 +1340,7 @@ static void s3c24xx_serial_pm(struct uart_port *port, unsigned int level,
 
 #define MAX_CLK_NAME_LENGTH 15
 
-static inline int s3c24xx_serial_getsource(struct uart_port *port)
+static inline u8 s3c24xx_serial_getsource(struct uart_port *port)
 {
 	const struct s3c24xx_uart_info *info = s3c24xx_port_to_info(port);
 	u32 ucon;
@@ -1353,8 +1353,7 @@ static inline int s3c24xx_serial_getsource(struct uart_port *port)
 	return ucon >> info->clksel_shift;
 }
 
-static void s3c24xx_serial_setsource(struct uart_port *port,
-			unsigned int clk_sel)
+static void s3c24xx_serial_setsource(struct uart_port *port, u8 clk_sel)
 {
 	const struct s3c24xx_uart_info *info = s3c24xx_port_to_info(port);
 	u32 ucon;
@@ -1373,14 +1372,15 @@ static void s3c24xx_serial_setsource(struct uart_port *port,
 
 static unsigned int s3c24xx_serial_getclk(struct s3c24xx_uart_port *ourport,
 			unsigned int req_baud, struct clk **best_clk,
-			unsigned int *clk_num)
+			u8 *clk_num)
 {
 	const struct s3c24xx_uart_info *info = ourport->info;
 	struct clk *clk;
 	unsigned long rate;
-	unsigned int cnt, baud, quot, best_quot = 0;
+	unsigned int baud, quot, best_quot = 0;
 	char clkname[MAX_CLK_NAME_LENGTH];
 	int calc_deviation, deviation = (1 << 30) - 1;
+	u8 cnt;
 
 	for (cnt = 0; cnt < info->num_clks; cnt++) {
 		/* Keep selected clock if provided */
@@ -1473,9 +1473,10 @@ static void s3c24xx_serial_set_termios(struct uart_port *port,
 	struct s3c24xx_uart_port *ourport = to_ourport(port);
 	struct clk *clk = ERR_PTR(-EINVAL);
 	unsigned long flags;
-	unsigned int baud, quot, clk_sel = 0;
+	unsigned int baud, quot;
 	unsigned int udivslot = 0;
 	u32 ulcon, umcon;
+	u8 clk_sel = 0;
 
 	/*
 	 * We don't support modem control lines.
@@ -1776,10 +1777,9 @@ static int s3c24xx_serial_enable_baudclk(struct s3c24xx_uart_port *ourport)
 	struct device *dev = ourport->port.dev;
 	const struct s3c24xx_uart_info *info = ourport->info;
 	char clk_name[MAX_CLK_NAME_LENGTH];
-	unsigned int clk_sel;
 	struct clk *clk;
-	int clk_num;
 	int ret;
+	u8 clk_sel, clk_num;
 
 	clk_sel = ourport->cfg->clk_sel ? : info->def_clk_sel;
 	for (clk_num = 0; clk_num < info->num_clks; clk_num++) {
@@ -2287,9 +2287,9 @@ s3c24xx_serial_get_options(struct uart_port *port, int *baud,
 {
 	struct clk *clk;
 	unsigned long rate;
-	unsigned int clk_sel;
 	u32 ulcon, ucon, ubrdiv;
 	char clk_name[MAX_CLK_NAME_LENGTH];
+	u8 clk_sel;
 
 	ulcon  = rd_regl(port, S3C2410_ULCON);
 	ucon   = rd_regl(port, S3C2410_UCON);