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Re: [PATCH] serial: lantiq: Do not swap register read/writes

To: Hauke Mehrtens <hauke@hauke-m.de>, gregkh@linuxfoundation.org
Subject: Re: [PATCH] serial: lantiq: Do not swap register read/writes
From: John Crispin <john@phrozen.org>
Date: Sun, 6 Jan 2019 21:38:29 +0100
Cc: linux-mips@linux-mips.org, linux-mips@vger.kernel.org, jslaby@suse.com, linux-serial@vger.kernel.org, songjun.wu@linux.intel.com
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On 06/01/2019 19:50, Hauke Mehrtens wrote:
The ltq_r32() and ltq_w32() macros use the __raw_readl() and
__raw_writel() functions which do not swap the value to little endian.
On the big endian vrx200 SoC the UART is operated in big endian IO mode,
the readl() and write() functions convert the value to little endian
first and then the driver does not work any more on this SoC.
Currently the vrx200 SoC selects the CONFIG_SWAP_IO_SPACE option,
without this option the serial driver would work, but PCI devices do not
work any more.

This patch makes the driver use the __raw_readl() and __raw_writel()
functions which do not swap the endianness. On big endian system it is
assumed that the device should be access in big endian IO mode and on a
little endian system it would be access in little endian mode.

Fixes: 89b8bd2082bb ("serial: lantiq: Use readl/writel instead of 
ltq_r32/ltq_w32")
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Acked-by: John Crispin <john@phrozen.org>
---
  drivers/tty/serial/lantiq.c | 36 +++++++++++++++++++-----------------
  1 file changed, 19 insertions(+), 17 deletions(-)

diff --git a/drivers/tty/serial/lantiq.c b/drivers/tty/serial/lantiq.c
index e052b69ceb98..9de9f0f239a1 100644
--- a/drivers/tty/serial/lantiq.c
+++ b/drivers/tty/serial/lantiq.c
@@ -114,9 +114,9 @@ struct ltq_uart_port {
static inline void asc_update_bits(u32 clear, u32 set, void __iomem *reg)
  {
-       u32 tmp = readl(reg);
+       u32 tmp = __raw_readl(reg);
- writel((tmp & ~clear) | set, reg);
+       __raw_writel((tmp & ~clear) | set, reg);
  }
static inline struct
@@ -144,7 +144,7 @@ lqasc_start_tx(struct uart_port *port)
  static void
  lqasc_stop_rx(struct uart_port *port)
  {
-       writel(ASCWHBSTATE_CLRREN, port->membase + LTQ_ASC_WHBSTATE);
+       __raw_writel(ASCWHBSTATE_CLRREN, port->membase + LTQ_ASC_WHBSTATE);
  }
static int
@@ -153,11 +153,12 @@ lqasc_rx_chars(struct uart_port *port)
        struct tty_port *tport = &port->state->port;
        unsigned int ch = 0, rsr = 0, fifocnt;
- fifocnt = readl(port->membase + LTQ_ASC_FSTAT) & ASCFSTAT_RXFFLMASK;
+       fifocnt = __raw_readl(port->membase + LTQ_ASC_FSTAT) &
+                 ASCFSTAT_RXFFLMASK;
        while (fifocnt--) {
                u8 flag = TTY_NORMAL;
                ch = readb(port->membase + LTQ_ASC_RBUF);
-               rsr = (readl(port->membase + LTQ_ASC_STATE)
+               rsr = (__raw_readl(port->membase + LTQ_ASC_STATE)
                        & ASCSTATE_ANY) | UART_DUMMY_UER_RX;
                tty_flip_buffer_push(tport);
                port->icount.rx++;
@@ -217,7 +218,7 @@ lqasc_tx_chars(struct uart_port *port)
                return;
        }
- while (((readl(port->membase + LTQ_ASC_FSTAT) &
+       while (((__raw_readl(port->membase + LTQ_ASC_FSTAT) &
                ASCFSTAT_TXFREEMASK) >> ASCFSTAT_TXFREEOFF) != 0) {
                if (port->x_char) {
                        writeb(port->x_char, port->membase + LTQ_ASC_TBUF);
@@ -245,7 +246,7 @@ lqasc_tx_int(int irq, void *_port)
        unsigned long flags;
        struct uart_port *port = (struct uart_port *)_port;
        spin_lock_irqsave(&ltq_asc_lock, flags);
-       writel(ASC_IRNCR_TIR, port->membase + LTQ_ASC_IRNCR);
+       __raw_writel(ASC_IRNCR_TIR, port->membase + LTQ_ASC_IRNCR);
        spin_unlock_irqrestore(&ltq_asc_lock, flags);
        lqasc_start_tx(port);
        return IRQ_HANDLED;
@@ -270,7 +271,7 @@ lqasc_rx_int(int irq, void *_port)
        unsigned long flags;
        struct uart_port *port = (struct uart_port *)_port;
        spin_lock_irqsave(&ltq_asc_lock, flags);
-       writel(ASC_IRNCR_RIR, port->membase + LTQ_ASC_IRNCR);
+       __raw_writel(ASC_IRNCR_RIR, port->membase + LTQ_ASC_IRNCR);
        lqasc_rx_chars(port);
        spin_unlock_irqrestore(&ltq_asc_lock, flags);
        return IRQ_HANDLED;
@@ -280,7 +281,8 @@ static unsigned int
  lqasc_tx_empty(struct uart_port *port)
  {
        int status;
-       status = readl(port->membase + LTQ_ASC_FSTAT) & ASCFSTAT_TXFFLMASK;
+       status = __raw_readl(port->membase + LTQ_ASC_FSTAT) &
+                ASCFSTAT_TXFFLMASK;
        return status ? 0 : TIOCSER_TEMT;
  }
@@ -313,12 +315,12 @@ lqasc_startup(struct uart_port *port)
        asc_update_bits(ASCCLC_DISS | ASCCLC_RMCMASK, (1 << ASCCLC_RMCOFFSET),
                port->membase + LTQ_ASC_CLC);
- writel(0, port->membase + LTQ_ASC_PISEL);
-       writel(
+       __raw_writel(0, port->membase + LTQ_ASC_PISEL);
+       __raw_writel(
                ((TXFIFO_FL << ASCTXFCON_TXFITLOFF) & ASCTXFCON_TXFITLMASK) |
                ASCTXFCON_TXFEN | ASCTXFCON_TXFFLU,
                port->membase + LTQ_ASC_TXFCON);
-       writel(
+       __raw_writel(
                ((RXFIFO_FL << ASCRXFCON_RXFITLOFF) & ASCRXFCON_RXFITLMASK)
                | ASCRXFCON_RXFEN | ASCRXFCON_RXFFLU,
                port->membase + LTQ_ASC_RXFCON);
@@ -350,7 +352,7 @@ lqasc_startup(struct uart_port *port)
                goto err2;
        }
- writel(ASC_IRNREN_RX | ASC_IRNREN_ERR | ASC_IRNREN_TX,
+       __raw_writel(ASC_IRNREN_RX | ASC_IRNREN_ERR | ASC_IRNREN_TX,
                port->membase + LTQ_ASC_IRNREN);
        return 0;
@@ -369,7 +371,7 @@ lqasc_shutdown(struct uart_port *port)
        free_irq(ltq_port->rx_irq, port);
        free_irq(ltq_port->err_irq, port);
- writel(0, port->membase + LTQ_ASC_CON);
+       __raw_writel(0, port->membase + LTQ_ASC_CON);
        asc_update_bits(ASCRXFCON_RXFEN, ASCRXFCON_RXFFLU,
                port->membase + LTQ_ASC_RXFCON);
        asc_update_bits(ASCTXFCON_TXFEN, ASCTXFCON_TXFFLU,
@@ -461,13 +463,13 @@ lqasc_set_termios(struct uart_port *port,
        asc_update_bits(ASCCON_BRS, 0, port->membase + LTQ_ASC_CON);
/* now we can write the new baudrate into the register */
-       writel(divisor, port->membase + LTQ_ASC_BG);
+       __raw_writel(divisor, port->membase + LTQ_ASC_BG);
/* turn the baudrate generator back on */
        asc_update_bits(0, ASCCON_R, port->membase + LTQ_ASC_CON);
/* enable rx */
-       writel(ASCWHBSTATE_SETREN, port->membase + LTQ_ASC_WHBSTATE);
+       __raw_writel(ASCWHBSTATE_SETREN, port->membase + LTQ_ASC_WHBSTATE);
spin_unlock_irqrestore(&ltq_asc_lock, flags); @@ -578,7 +580,7 @@ lqasc_console_putchar(struct uart_port *port, int ch)
                return;
do {
-               fifofree = (readl(port->membase + LTQ_ASC_FSTAT)
+               fifofree = (__raw_readl(port->membase + LTQ_ASC_FSTAT)
                        & ASCFSTAT_TXFREEMASK) >> ASCFSTAT_TXFREEOFF;
        } while (fifofree == 0);
        writeb(ch, port->membase + LTQ_ASC_TBUF);

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