[PATCH] serial: imx: get rid of registers shadowing

[Sergey Organov]

Neither registers shadowing is functionally needed as all the registers are
read-write, nor the shadowing makes much sense for speed-up, as most speed
critical reads/writes (of data Rx/Tx registers) are not shadowed anyway.
Moreover, the shadowing code is obviously pure overhead on the write path.

Get rid of the shadowing code and variables due to above considerations.

Signed-off-by: Sergey Organov <sorganov at gmail.com>
---

NOTE: This patch is extracted from patch series "[PATCH 0/8] serial: imx:
work-around for hardware RX flood, and then isr improvements" due to
objection of Uwe Kleine-König <u.kleine-koenig at pengutronix.de>. I still
believe this is an improvement, so I re-submit the patch separately.

 drivers/tty/serial/imx.c | 65 ++--------------------------------------
 1 file changed, 3 insertions(+), 62 deletions(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 757825edb0cd..f4e2db21d0fe 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -210,13 +210,6 @@ struct imx_port {
 
 	struct mctrl_gpios *gpios;
 
-	/* shadow registers */
-	unsigned int ucr1;
-	unsigned int ucr2;
-	unsigned int ucr3;
-	unsigned int ucr4;
-	unsigned int ufcr;
-
 	/* DMA fields */
 	unsigned int		dma_is_enabled:1;
 	unsigned int		dma_is_rxing:1;
@@ -273,59 +266,14 @@ static const struct of_device_id imx_uart_dt_ids[] = {
 };
 MODULE_DEVICE_TABLE(of, imx_uart_dt_ids);
 
-static void imx_uart_writel(struct imx_port *sport, u32 val, u32 offset)
+static inline void imx_uart_writel(struct imx_port *sport, u32 val, u32 offset)
 {
-	switch (offset) {
-	case UCR1:
-		sport->ucr1 = val;
-		break;
-	case UCR2:
-		sport->ucr2 = val;
-		break;
-	case UCR3:
-		sport->ucr3 = val;
-		break;
-	case UCR4:
-		sport->ucr4 = val;
-		break;
-	case UFCR:
-		sport->ufcr = val;
-		break;
-	default:
-		break;
-	}
 	writel(val, sport->port.membase + offset);
 }
 
-static u32 imx_uart_readl(struct imx_port *sport, u32 offset)
+static inline u32 imx_uart_readl(struct imx_port *sport, u32 offset)
 {
-	switch (offset) {
-	case UCR1:
-		return sport->ucr1;
-		break;
-	case UCR2:
-		/*
-		 * UCR2_SRST is the only bit in the cached registers that might
-		 * differ from the value that was last written. As it only
-		 * automatically becomes one after being cleared, reread
-		 * conditionally.
-		 */
-		if (!(sport->ucr2 & UCR2_SRST))
-			sport->ucr2 = readl(sport->port.membase + offset);
-		return sport->ucr2;
-		break;
-	case UCR3:
-		return sport->ucr3;
-		break;
-	case UCR4:
-		return sport->ucr4;
-		break;
-	case UFCR:
-		return sport->ufcr;
-		break;
-	default:
-		return readl(sport->port.membase + offset);
-	}
+	return readl(sport->port.membase + offset);
 }
 
 static inline unsigned imx_uart_uts_reg(struct imx_port *sport)
@@ -2340,13 +2288,6 @@ static int imx_uart_probe(struct platform_device *pdev)
 		return ret;
 	}
 
-	/* initialize shadow register values */
-	sport->ucr1 = readl(sport->port.membase + UCR1);
-	sport->ucr2 = readl(sport->port.membase + UCR2);
-	sport->ucr3 = readl(sport->port.membase + UCR3);
-	sport->ucr4 = readl(sport->port.membase + UCR4);
-	sport->ufcr = readl(sport->port.membase + UFCR);
-
 	ret = uart_get_rs485_mode(&sport->port);
 	if (ret) {
 		clk_disable_unprepare(sport->clk_ipg);

base-commit: 40c18f363a0806d4f566e8a9a9bd2d7766a72cf5
-- 
2.30.1