diff options
| author | Sergey Organov <sorganov@gmail.com> | 2019-08-28 21:37:54 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-09-04 12:43:55 +0200 |
| commit | d47bcb4a6cf0be5f3b390fe3fc12416034f86ae2 (patch) | |
| tree | 018f7985745a9c00b5148a828bde0f4c3ed0c513 | |
| parent | 85f30fbf32d1e8a55c5c563aaf8a35488c6d9745 (diff) | |
serial: imx: fix data breakage on termios change
imx_set_termios(): avoid writing baud rate divider registers when the
values to be written are the same as current. Any writing seems to
restart transmission/receiving logic in the hardware, that leads to
data breakage even when rate doesn't in fact change. E.g., user
switches RTS/CTS handshake and suddenly gets broken bytes.
Signed-off-by: Sergey Organov <sorganov@gmail.com>
Link: https://lore.kernel.org/r/1567017475-11919-5-git-send-email-sorganov@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/tty/serial/imx.c | 19 |
1 files changed, 16 insertions, 3 deletions
diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index cc3783c0a7ed..e89045a085fb 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -1545,7 +1545,7 @@ imx_uart_set_termios(struct uart_port *port, struct ktermios *termios, unsigned int baud, quot; unsigned int old_csize = old ? old->c_cflag & CSIZE : CS8; unsigned long div; - unsigned long num, denom; + unsigned long num, denom, old_ubir, old_ubmr; uint64_t tdiv64; /* @@ -1670,8 +1670,21 @@ imx_uart_set_termios(struct uart_port *port, struct ktermios *termios, ufcr = (ufcr & (~UFCR_RFDIV)) | UFCR_RFDIV_REG(div); imx_uart_writel(sport, ufcr, UFCR); - imx_uart_writel(sport, num, UBIR); - imx_uart_writel(sport, denom, UBMR); + /* + * Two registers below should always be written both and in this + * particular order. One consequence is that we need to check if any of + * them changes and then update both. We do need the check for change + * as even writing the same values seem to "restart" + * transmission/receiving logic in the hardware, that leads to data + * breakage even when rate doesn't in fact change. E.g., user switches + * RTS/CTS handshake and suddenly gets broken bytes. + */ + old_ubir = imx_uart_readl(sport, UBIR); + old_ubmr = imx_uart_readl(sport, UBMR); + if (old_ubir != num || old_ubmr != denom) { + imx_uart_writel(sport, num, UBIR); + imx_uart_writel(sport, denom, UBMR); + } if (!imx_uart_is_imx1(sport)) imx_uart_writel(sport, sport->port.uartclk / div / 1000, |