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serial: imx: implement shadow registers for UCRx and UFCR

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This reduces the amount of read accesses to the register space by
shadowing the values for five registers that only change on writing
them. There is a single bit in UCR2 that might change without being
written to it, this is handled accordingly.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Uwe Kleine-König 2018-03-02 11:07:20 +01:00 committed by Greg Kroah-Hartman
parent 27c844261b
commit 3a0ab62f43
1 changed files with 59 additions and 1 deletions
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60
drivers/tty/serial/imx.c
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@ -204,6 +204,13 @@ 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;
@ -275,12 +282,56 @@ MODULE_DEVICE_TABLE(of, imx_uart_dt_ids);
static 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)
{
return readl(sport->port.membase + 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
* clears after being set, 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);
}
}
static inline unsigned uts_reg(struct imx_port *sport)
@ -2136,6 +2187,13 @@ static int serial_imx_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);
uart_get_rs485_mode(&pdev->dev, &sport->port.rs485);
if (sport->port.rs485.flags & SER_RS485_ENABLED &&