[PATCH v2] serial: Use -EAGAIN in getc and putc
Pali Rohár
pali at kernel.org
Sun Dec 11 00:31:21 CET 2022
U-Boot serial code already handles -EAGAIN value from getc and putc
callbacks. So change drivers code to return -EAGAIN when HW is busy instead
of doing its own busy loop and waiting until HW is ready.
Signed-off-by: Pali Rohár <pali at kernel.org>
---
Changes in v2:
* Fix serial_lpuart.c code after Tom's review
* Add serial_mpc8xx.c change
To prevent merge conflicts, please apply this patch *after* this:
http://patchwork.ozlabs.org/project/uboot/patch/20221210232744.15600-1-pali@kernel.org/
---
drivers/serial/serial_arc.c | 8 +++----
drivers/serial/serial_lpuart.c | 36 ++++++++++++-----------------
drivers/serial/serial_mpc8xx.c | 12 ++++------
drivers/serial/serial_mvebu_a3700.c | 8 +++----
4 files changed, 28 insertions(+), 36 deletions(-)
diff --git a/drivers/serial/serial_arc.c b/drivers/serial/serial_arc.c
index b2d95bdbe18d..c2fc8a901e25 100644
--- a/drivers/serial/serial_arc.c
+++ b/drivers/serial/serial_arc.c
@@ -53,8 +53,8 @@ static int arc_serial_putc(struct udevice *dev, const char c)
struct arc_serial_plat *plat = dev_get_plat(dev);
struct arc_serial_regs *const regs = plat->reg;
- while (!(readb(®s->status) & UART_TXEMPTY))
- ;
+ if (!(readb(®s->status) & UART_TXEMPTY))
+ return -EAGAIN;
writeb(c, ®s->data);
@@ -83,8 +83,8 @@ static int arc_serial_getc(struct udevice *dev)
struct arc_serial_plat *plat = dev_get_plat(dev);
struct arc_serial_regs *const regs = plat->reg;
- while (!arc_serial_tstc(regs))
- ;
+ if (!arc_serial_tstc(regs))
+ return -EAGAIN;
/* Check for overflow errors */
if (readb(®s->status) & UART_OVERFLOW_ERR)
diff --git a/drivers/serial/serial_lpuart.c b/drivers/serial/serial_lpuart.c
index 07941c29ed74..51e66abdbc15 100644
--- a/drivers/serial/serial_lpuart.c
+++ b/drivers/serial/serial_lpuart.c
@@ -168,23 +168,24 @@ static void _lpuart_serial_setbrg(struct udevice *dev,
static int _lpuart_serial_getc(struct lpuart_serial_plat *plat)
{
struct lpuart_fsl *base = plat->reg;
- while (!(__raw_readb(&base->us1) & (US1_RDRF | US1_OR)))
- schedule();
+ if (!(__raw_readb(&base->us1) & (US1_RDRF | US1_OR)))
+ return -EAGAIN;
barrier();
return __raw_readb(&base->ud);
}
-static void _lpuart_serial_putc(struct lpuart_serial_plat *plat,
+static int _lpuart_serial_putc(struct lpuart_serial_plat *plat,
const char c)
{
struct lpuart_fsl *base = plat->reg;
- while (!(__raw_readb(&base->us1) & US1_TDRE))
- schedule();
+ if (!(__raw_readb(&base->us1) & US1_TDRE))
+ return -EAGAIN;
__raw_writeb(c, &base->ud);
+ return 0;
}
/* Test whether a character is in the RX buffer */
@@ -328,10 +329,9 @@ static int _lpuart32_serial_getc(struct lpuart_serial_plat *plat)
u32 stat, val;
lpuart_read32(plat->flags, &base->stat, &stat);
- while ((stat & STAT_RDRF) == 0) {
+ if ((stat & STAT_RDRF) == 0) {
lpuart_write32(plat->flags, &base->stat, STAT_FLAGS);
- schedule();
- lpuart_read32(plat->flags, &base->stat, &stat);
+ return -EAGAIN;
}
lpuart_read32(plat->flags, &base->data, &val);
@@ -343,22 +343,18 @@ static int _lpuart32_serial_getc(struct lpuart_serial_plat *plat)
return val & 0x3ff;
}
-static void _lpuart32_serial_putc(struct lpuart_serial_plat *plat,
+static int _lpuart32_serial_putc(struct lpuart_serial_plat *plat,
const char c)
{
struct lpuart_fsl_reg32 *base = plat->reg;
u32 stat;
- while (true) {
- lpuart_read32(plat->flags, &base->stat, &stat);
-
- if ((stat & STAT_TDRE))
- break;
-
- schedule();
- }
+ lpuart_read32(plat->flags, &base->stat, &stat);
+ if (!(stat & STAT_TDRE))
+ return -EAGAIN;
lpuart_write32(plat->flags, &base->data, c);
+ return 0;
}
/* Test whether a character is in the RX buffer */
@@ -453,11 +449,9 @@ static int lpuart_serial_putc(struct udevice *dev, const char c)
struct lpuart_serial_plat *plat = dev_get_plat(dev);
if (is_lpuart32(dev))
- _lpuart32_serial_putc(plat, c);
- else
- _lpuart_serial_putc(plat, c);
+ return _lpuart32_serial_putc(plat, c);
- return 0;
+ return _lpuart_serial_putc(plat, c);
}
static int lpuart_serial_pending(struct udevice *dev, bool input)
diff --git a/drivers/serial/serial_mpc8xx.c b/drivers/serial/serial_mpc8xx.c
index 808a40f503ea..b8d6a81b650f 100644
--- a/drivers/serial/serial_mpc8xx.c
+++ b/drivers/serial/serial_mpc8xx.c
@@ -178,14 +178,13 @@ static int serial_mpc8xx_putc(struct udevice *dev, const char c)
rtx = (struct serialbuffer __iomem *)&cpmp->cp_dpmem[CPM_SERIAL_BASE];
- /* Wait for last character to go. */
+ if (in_be16(&rtx->txbd.cbd_sc) & BD_SC_READY)
+ return -EAGAIN;
+
out_8(&rtx->txbuf, c);
out_be16(&rtx->txbd.cbd_datlen, 1);
setbits_be16(&rtx->txbd.cbd_sc, BD_SC_READY);
- while (in_be16(&rtx->txbd.cbd_sc) & BD_SC_READY)
- schedule();
-
return 0;
}
@@ -199,9 +198,8 @@ static int serial_mpc8xx_getc(struct udevice *dev)
rtx = (struct serialbuffer __iomem *)&cpmp->cp_dpmem[CPM_SERIAL_BASE];
- /* Wait for character to show up. */
- while (in_be16(&rtx->rxbd.cbd_sc) & BD_SC_EMPTY)
- schedule();
+ if (in_be16(&rtx->rxbd.cbd_sc) & BD_SC_EMPTY)
+ return -EAGAIN;
/* the characters are read one by one,
* use the rxindex to know the next char to deliver
diff --git a/drivers/serial/serial_mvebu_a3700.c b/drivers/serial/serial_mvebu_a3700.c
index 0fcd7e88acee..b2017c645565 100644
--- a/drivers/serial/serial_mvebu_a3700.c
+++ b/drivers/serial/serial_mvebu_a3700.c
@@ -40,8 +40,8 @@ static int mvebu_serial_putc(struct udevice *dev, const char ch)
struct mvebu_plat *plat = dev_get_plat(dev);
void __iomem *base = plat->base;
- while (readl(base + UART_STATUS_REG) & UART_STATUS_TXFIFO_FULL)
- ;
+ if (readl(base + UART_STATUS_REG) & UART_STATUS_TXFIFO_FULL)
+ return -EAGAIN;
writel(ch, base + UART_TX_REG);
@@ -53,8 +53,8 @@ static int mvebu_serial_getc(struct udevice *dev)
struct mvebu_plat *plat = dev_get_plat(dev);
void __iomem *base = plat->base;
- while (!(readl(base + UART_STATUS_REG) & UART_STATUS_RX_RDY))
- ;
+ if (!(readl(base + UART_STATUS_REG) & UART_STATUS_RX_RDY))
+ return -EAGAIN;
return readl(base + UART_RX_REG) & 0xff;
}
--
2.20.1
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