Re: [PATCH 10/12] serial: 8250_dw: Add Sophgo SG2042 support

[Ben Dooks]

On 15/09/2023 11:23, Emil Renner Berthing wrote:
> Krzysztof Kozlowski wrote:
> > On 15/09/2023 12:02, Emil Renner Berthing wrote:
> > > Krzysztof Kozlowski wrote:
> > > > On 15/09/2023 09:25, Wang Chen wrote:
> > > > > From: Emil Renner Berthing <emil.renner.berthing@xxxxxxxxxxxxx>
> > > > >
> > > > > Add quirk to skip setting the input clock rate for the uarts on the
> > > > > Sophgo SG2042 SoC similar to the StarFive JH7100.
> > > > >
> > > > > Signed-off-by: Emil Renner Berthing <emil.renner.berthing@xxxxxxxxxxxxx>
> > > >
> > > > Missing SoB.
> > > >
> > > > > ---
> > > > >   drivers/tty/serial/8250/8250_dw.c | 5 +++--
> > > > >   1 file changed, 3 insertions(+), 2 deletions(-)
> > > > >
> > > > > diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
> > > > > index f4cafca1a7da..6c344877a07f 100644
> > > > > --- a/drivers/tty/serial/8250/8250_dw.c
> > > > > +++ b/drivers/tty/serial/8250/8250_dw.c
> > > > > @@ -770,7 +770,7 @@ static const struct dw8250_platform_data dw8250_renesas_rzn1_data = {
> > > > >   	.quirks = DW_UART_QUIRK_IS_DMA_FC,
> > > > >   };
> > > > >
> > > > > -static const struct dw8250_platform_data dw8250_starfive_jh7100_data = {
> > > > > +static const struct dw8250_platform_data dw8250_skip_set_rate_data = {
> > > >
> > > > Why? What is wrong with old name?
> > > >
> > > > >   	.usr_reg = DW_UART_USR,
> > > > >   	.quirks = DW_UART_QUIRK_SKIP_SET_RATE,
> > > > >   };
> > > > > @@ -780,7 +780,8 @@ static const struct of_device_id dw8250_of_match[] = {
> > > > >   	{ .compatible = "cavium,octeon-3860-uart", .data = &dw8250_octeon_3860_data },
> > > > >   	{ .compatible = "marvell,armada-38x-uart", .data = &dw8250_armada_38x_data },
> > > > >   	{ .compatible = "renesas,rzn1-uart", .data = &dw8250_renesas_rzn1_data },
> > > > > -	{ .compatible = "starfive,jh7100-uart", .data = &dw8250_starfive_jh7100_data },
> > > > > +	{ .compatible = "sophgo,sg2042-uart", .data = &dw8250_skip_set_rate_data },
> > > > > +	{ .compatible = "starfive,jh7100-uart", .data = &dw8250_skip_set_rate_data },
> > > >
> > > > So devices are fully compatible? Then use compatibility and drop this
> > > > patch entirely.
> > >
> > > I'm fine with this, but these are two different companies and SoCs that just
> > > happens to have both implemented the Designware UART with an inflexible input
> > > clock. So if fx. a real quirk is found on the JH7110 then we'd need to either
> > > change the compatible on an unrelated SoC or change compatible on the JH7110 to
> >
> > Wait, why? The compatible is still there, so you just add here proper
> > entry, if ever needed.
>
> Sorry, I messed up my example by writing JH7110 where I meant JH7100
>
> > > something like "starfive,jh7100-uart-with-quirk" and "starfive,jh7100-uart" will
> > > forever be a quirky way to spell "dw8250 with inflexible input clock".
> > > Is that how device trees are supposed to work?
> >
> > I don't get this part. But anyway if the blocks are really designed or
> > done independently and there is no shared part, except the DWC block,
> > then indeed the compatibility might be just a coincidence...
>
> It is. Sophgo and StarFive are not the same company. Sophgo are using RISC-V
> cores from T-Head and StarFive are using cores from SiFive. They just happen to
> both use the Designware UART in the same way.

Out of interest, what's the issue with just providing an fixed clock in
the device tree for these machines?


--
Ben Dooks				http://www.codethink.co.uk/
Senior Engineer				Codethink - Providing Genius

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