Re: [PATCH v2 16/20] tty: serial: samsung: Add gs101 compatible and SoC data

[Peter Griffin <peter.griffin@linaro.org>]

Hi Greg,

Thanks for the review.

On Wed, 11 Oct 2023 at 08:47, Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Tue, Oct 10, 2023 at 11:49:24PM +0100, Peter Griffin wrote:
> > Add serial driver data for Google Tensor gs101 SoC.
> >
> > Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
> > ---
> >  drivers/tty/serial/samsung_tty.c | 12 ++++++++++++
> >  1 file changed, 12 insertions(+)
> >
> > diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
> > index 07fb8a9dac63..79a1a184d5c1 100644
> > --- a/drivers/tty/serial/samsung_tty.c
> > +++ b/drivers/tty/serial/samsung_tty.c
> > @@ -2597,14 +2597,21 @@ static const struct s3c24xx_serial_drv_data exynos850_serial_drv_data = {
> >       .fifosize = { 256, 64, 64, 64 },
> >  };
> >
> > +static const struct s3c24xx_serial_drv_data gs101_serial_drv_data = {
> > +     EXYNOS_COMMON_SERIAL_DRV_DATA(),
> > +     .fifosize = { 256, 64, 64, 64 },
> > +};
>
> Why are you duplicating a structure that is already in the same file?
> What is the benifit here?

There is a mistake here, the struct shouldn't be the same as e850 it
should look like this

static const struct s3c24xx_serial_drv_data gs101_serial_drv_data = {
     EXYNOS_COMMON_SERIAL_DRV_DATA(),
     /* rely on samsung,uart-fifosize DT property for fifosize */
     .fifosize = { 0 },
};

This then allows the fifosize to be taken from the samsung,uart-fifosize
DT property for each of the 19 UARTs on this SoC.

>
> >  #define EXYNOS4210_SERIAL_DRV_DATA (&exynos4210_serial_drv_data)
> >  #define EXYNOS5433_SERIAL_DRV_DATA (&exynos5433_serial_drv_data)
> >  #define EXYNOS850_SERIAL_DRV_DATA (&exynos850_serial_drv_data)
> > +#define GS101_SERIAL_DRV_DATA (&gs101_serial_drv_data)
>
> What is "GS101"?

gs101 is the name of the SoC in Pixel 6, 6 pro, 6a phones. I've put
some more info
about the various names of the SoC in the bindings documentation. See
https://lore.kernel.org/linux-arm-kernel/20231010224928.2296997-9-peter.griffin@linaro.org/T/#mb45492e58de0bef566df8cdf6191ab8f96f0cf99

>
> >  #else
> >  #define EXYNOS4210_SERIAL_DRV_DATA NULL
> >  #define EXYNOS5433_SERIAL_DRV_DATA NULL
> >  #define EXYNOS850_SERIAL_DRV_DATA NULL
> > +#define GS101_SERIAL_DRV_DATA NULL
> >  #endif
> >
> >  #ifdef CONFIG_ARCH_APPLE
> > @@ -2688,6 +2695,9 @@ static const struct platform_device_id s3c24xx_serial_driver_ids[] = {
> >       }, {
> >               .name           = "artpec8-uart",
> >               .driver_data    = (kernel_ulong_t)ARTPEC8_SERIAL_DRV_DATA,
> > +     }, {
> > +             .name           = "gs101-uart",
> > +             .driver_data    = (kernel_ulong_t)GS101_SERIAL_DRV_DATA,
> >       },
> >       { },
> >  };
> > @@ -2709,6 +2719,8 @@ static const struct of_device_id s3c24xx_uart_dt_match[] = {
> >               .data = EXYNOS850_SERIAL_DRV_DATA },
> >       { .compatible = "axis,artpec8-uart",
> >               .data = ARTPEC8_SERIAL_DRV_DATA },
> > +     { .compatible = "google,gs101-uart",
> > +             .data =  GS101_SERIAL_DRV_DATA },
>
> Why aren't you just listing this hardware as the same one above?  There
> doesn't need to be a new entry if you just fix up the DT for the board
> to declare it as the proper type of device.  No need to keep adding new
> entries that do the exact same thing, we don't normally like that at all
> for other bus types, why is DT different?
>

I believe Krzysztof already answered this from a dt maintainer point of view.

regards,

Peter.