linux-kernel - Re: [PATCH v2 2/2] serial: 8250

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Message-ID: <29d8e2a6-d0e7-0f74-1f5c-4f285ec1e9ee@linux.intel.com>
Date: Mon, 21 Oct 2024 11:52:38 +0300 (EEST)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Inochi Amaoto <inochiama@...il.com>
cc: Chen Wang <unicorn_wang@...look.com>, 
    Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
    Jiri Slaby <jirislaby@...nel.org>, Rob Herring <robh@...nel.org>, 
    Krzysztof Kozlowski <krzk+dt@...nel.org>, 
    Conor Dooley <conor+dt@...nel.org>, 
    Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, 
    Paul Walmsley <paul.walmsley@...ive.com>, 
    Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
    Inochi Amaoto <inochiama@...look.com>, Yixun Lan <dlan@...too.org>, 
    LKML <linux-kernel@...r.kernel.org>, 
    linux-serial <linux-serial@...r.kernel.org>, devicetree@...r.kernel.org, 
    linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v2 2/2] serial: 8250_dw: Add Sophgo SG2044 quirk

On Mon, 21 Oct 2024, Inochi Amaoto wrote:

> SG2044 relys on an internal divisor when calculating bitrate, which
> means a wrong clock for the most common bitrates. So add a quirk for
> this uart device to skip the set rate call and only relys on the
> internal UART divisor.
> 
> Signed-off-by: Inochi Amaoto <inochiama@...il.com>

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>

I wonder though does this mean the numbers userspace can read from kernel 
are bogus and if something can be done about that?

-- 
 i.

> ---
>  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 ab9e7f204260..51894c93c8a3 100644
> --- a/drivers/tty/serial/8250/8250_dw.c
> +++ b/drivers/tty/serial/8250/8250_dw.c
> @@ -750,7 +750,7 @@ static const struct dw8250_platform_data dw8250_renesas_rzn1_data = {
>  	.quirks = DW_UART_QUIRK_CPR_VALUE | 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 = {
>  	.usr_reg = DW_UART_USR,
>  	.quirks = DW_UART_QUIRK_SKIP_SET_RATE,
>  };
> @@ -760,7 +760,8 @@ 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,sg2044-uart", .data = &dw8250_skip_set_rate_data },
> +	{ .compatible = "starfive,jh7100-uart", .data = &dw8250_skip_set_rate_data },
>  	{ /* Sentinel */ }
>  };
>  MODULE_DEVICE_TABLE(of, dw8250_of_match);
>