On Sun, Dec 04, 2022 at 01:36:55PM +0100, Pali Rohár wrote:

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@kernel.org Reviewed-by: Simon Glass sjg@chromium.org Reviewed-by: Stefan Roese sr@denx.de

[snip]

diff --git a/drivers/serial/serial_lpuart.c b/drivers/serial/serial_lpuart.c index ff576da516d4..d7259d531b55 100644 --- a/drivers/serial/serial_lpuart.c +++ b/drivers/serial/serial_lpuart.c @@ -168,8 +168,8 @@ 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();

@@ -181,8 +181,8 @@ static void _lpuart_serial_putc(struct lpuart_serial_plat *plat, { 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);

}

This is non-trivially not right for this driver. ->putc here is set to lpuart_serial_putc which calls _lpuart_serial_putc OR _lpuart32_serial_putc, so there's the lpuart32 cases to address, and then lpuart_serial_putc needs to just return whatever one it called rather than always returning 0.

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@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@... --- 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(&regs->status) & UART_TXEMPTY)) - ; + if (!(readb(&regs->status) & UART_TXEMPTY)) + return -EAGAIN;

writeb(c, &regs->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(&regs->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; }