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From:   wenhua lin <wenhua.lin1994@gmail.com>
Date:   Wed, 9 Aug 2023 19:27:02 +0800
Message-ID: <CAB9BWhf9e6cmLn6qHQqeM0-8kWf-mH7kWz2YvKvcpzXVkk2-=Q@mail.gmail.com>
Subject: Re: [PATCH] serial: sprd: Support 12 uart ports
To:     Baolin Wang <baolin.wang@linux.alibaba.com>
Cc:     Wenhua Lin <Wenhua.Lin@unisoc.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jiri Slaby <jirislaby@kernel.org>,
        Orson Zhai <orsonzhai@gmail.com>,
        Chunyan Zhang <zhang.lyra@gmail.com>,
        linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org,
        Xiongpeng Wu <xiongpeng.wu@unisoc.com>
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On Wed, Aug 9, 2023 at 2:27=E2=80=AFPM Baolin Wang
<baolin.wang@linux.alibaba.com> wrote:
>
>
>
> On 8/9/2023 1:52 PM, wenhua lin wrote:
> > The change of the max ports is to adapt to an new
> > SPRD serial hardware,also is backward-compatibility with old hardware.
>
> Again, DO NOT top-posting! Thanks.

Thank you for your correction.


>
> >>
> >> On 8/7/2023 4:07 PM, Wenhua Lin wrote:
> >>> From: Wenhua Lin <wenhua.lin@unisoc.com>
> >>>
> >>> Support 12 uart ports, which can solve the problem
> >>> of insufficient uart ports.
> >>
> >> This sounds incorrect to me.
> >> If this is a software bug, please add a Fixes tag to backport for stab=
le
> >> kernels. If the change of the max ports is only avaliable on the new
> >> SPRD serial hardware, you should ensure the change is
> >> backward-compatibility with old hardware.
>
> This is not backward-compatibility. Please see 'sprd_uart_driver'
> structure as below:
>
> static struct uart_driver sprd_uart_driver =3D {
>         .owner =3D THIS_MODULE,
>         .driver_name =3D "sprd_serial",
>         .dev_name =3D SPRD_TTY_NAME,
>         .major =3D 0,
>         .minor =3D 0,
>         .nr =3D UART_NR_MAX,
>         .cons =3D SPRD_CONSOLE,
> };
>
> That means you will still register 12 UART ports in the tty for old
> serial hardwares which actually only support 8 UART ports, and if users
> want to use another 4 ports which are not supported in the hardware,
> then system crashes.
>
> So I think you should add a SoC data in 'serial_ids' to change the
> number of UART port according to different SoC.
>

Thank you for your valuable comments, we should probably consider
how to make changes based on your suggestions.

> >>> Signed-off-by: Wenhua Lin <wenhua.lin@unisoc.com>
> >>> ---
> >>>    drivers/tty/serial/sprd_serial.c | 2 +-
> >>>    1 file changed, 1 insertion(+), 1 deletion(-)
> >>>
> >>> diff --git a/drivers/tty/serial/sprd_serial.c b/drivers/tty/serial/sp=
rd_serial.c
> >>> index b58f51296ace..2774df490899 100644
> >>> --- a/drivers/tty/serial/sprd_serial.c
> >>> +++ b/drivers/tty/serial/sprd_serial.c
> >>> @@ -22,7 +22,7 @@
> >>>    #include <linux/tty_flip.h>
> >>>
> >>>    /* device name */
> >>> -#define UART_NR_MAX          8
> >>> +#define UART_NR_MAX          12
> >>>    #define SPRD_TTY_NAME               "ttyS"
> >>>    #define SPRD_FIFO_SIZE              128
> >>>    #define SPRD_DEF_RATE               26000000