Re: [PATCH] serial: sprd: Support 12 uart ports

[Baolin Wang]

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.

> > On 8/7/2023 4:07 PM, Wenhua Lin wrote:
> > > From: Wenhua Lin <wenhua.lin@xxxxxxxxxx>
> > >
> > > 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 stable
> > 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 = {
	.owner = THIS_MODULE,
	.driver_name = "sprd_serial",
	.dev_name = SPRD_TTY_NAME,
	.major = 0,
	.minor = 0,
	.nr = UART_NR_MAX,
	.cons = 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.

> > > Signed-off-by: Wenhua Lin <wenhua.lin@xxxxxxxxxx>
> > > ---
> > >    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/sprd_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