From: Hugo Villeneuve <hugo@hugovil.com>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: jirislaby@kernel.org, fvallee@eukrea.fr,
linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org,
Hugo Villeneuve <hvilleneuve@dimonoff.com>,
stable@vger.kernel.org
Subject: Re: [PATCH v2 01/15] serial: sc16is7xx: remove useless enable of enhanced features
Date: Thu, 2 Oct 2025 11:53:33 -0400 [thread overview]
Message-ID: <20251002115333.23f1c4a535a4a6f64cdca8a2@hugovil.com> (raw)
In-Reply-To: <2025100219-neon-litter-24c0@gregkh>
Hi Greg,
On Thu, 2 Oct 2025 17:43:52 +0200
Greg KH <gregkh@linuxfoundation.org> wrote:
> On Thu, Oct 02, 2025 at 10:57:24AM -0400, Hugo Villeneuve wrote:
> > From: Hugo Villeneuve <hvilleneuve@dimonoff.com>
> >
> > Commit 43c51bb573aa ("sc16is7xx: make sure device is in suspend once
> > probed") permanently enabled access to the enhanced features in
> > sc16is7xx_probe(), and it is never disabled after that.
> >
> > Therefore, remove useless re-enable of enhanced features in
> > sc16is7xx_set_baud().
> >
> > Fixes: 43c51bb573aa ("sc16is7xx: make sure device is in suspend once probed")
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
> > ---
> > drivers/tty/serial/sc16is7xx.c | 7 -------
> > 1 file changed, 7 deletions(-)
> >
> > diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
> > index 1a2c4c14f6aac..c7435595dce13 100644
> > --- a/drivers/tty/serial/sc16is7xx.c
> > +++ b/drivers/tty/serial/sc16is7xx.c
> > @@ -588,13 +588,6 @@ static int sc16is7xx_set_baud(struct uart_port *port, int baud)
> > div /= prescaler;
> > }
> >
> > - /* Enable enhanced features */
> > - sc16is7xx_efr_lock(port);
> > - sc16is7xx_port_update(port, SC16IS7XX_EFR_REG,
> > - SC16IS7XX_EFR_ENABLE_BIT,
> > - SC16IS7XX_EFR_ENABLE_BIT);
> > - sc16is7xx_efr_unlock(port);
> > -
> > /* If bit MCR_CLKSEL is set, the divide by 4 prescaler is activated. */
> > sc16is7xx_port_update(port, SC16IS7XX_MCR_REG,
> > SC16IS7XX_MCR_CLKSEL_BIT,
> > --
> > 2.39.5
> >
> >
>
> Why is this needed for stable kernels? It's useless, what is it
> harming?
It is useless, and doing no "harm", but since the device is on a SPI
or I2C bus, this is inefficient as it takes precious cycles on these
busses.
> If so, please send it separately, not as a part of a larger series.
That is why this patch is the first in the series, so that it could be
easily backported. But I can send it separately, sure.
Hugo.
next prev parent reply other threads:[~2025-10-02 15:53 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-02 14:57 [PATCH v2 00/15] serial: sc16is7xx: register access fixes and improvements Hugo Villeneuve
2025-10-02 14:57 ` [PATCH v2 01/15] serial: sc16is7xx: remove useless enable of enhanced features Hugo Villeneuve
2025-10-02 15:43 ` Greg KH
2025-10-02 15:53 ` Hugo Villeneuve [this message]
2025-10-02 14:57 ` [PATCH v2 02/15] serial: sc16is7xx: rename LCR macros to better reflect usage Hugo Villeneuve
2025-10-02 14:57 ` [PATCH v2 03/15] serial: sc16is7xx: rename EFR mutex with generic name Hugo Villeneuve
2025-10-02 14:57 ` [PATCH v2 04/15] serial: sc16is7xx: define common register access function Hugo Villeneuve
2025-10-02 14:57 ` [PATCH v2 05/15] serial: sc16is7xx: remove unnecessary pointer cast Hugo Villeneuve
2025-10-02 14:57 ` [PATCH v2 06/15] serial: sc16is7xx: use guards for simple mutex locks Hugo Villeneuve
2025-10-02 14:57 ` [PATCH v2 07/15] serial: sc16is7xx: drop -ENOMEM error message Hugo Villeneuve
2025-10-02 14:57 ` [PATCH v2 08/15] serial: sc16is7xx: declare SPR/TLR/XOFF2 register as volatile Hugo Villeneuve
2025-10-02 14:57 ` [PATCH v2 09/15] serial: sc16is7xx: move port/channel init to separate function Hugo Villeneuve
2025-10-02 14:57 ` [PATCH v2 10/15] serial: sc16is7xx: simplify to_sc16is7xx_one() with a single parameter Hugo Villeneuve
2025-10-02 14:57 ` [PATCH v2 11/15] serial: sc16is7xx: Kconfig: allow building with COMPILE_TEST Hugo Villeneuve
2025-10-02 14:57 ` [PATCH v2 12/15] serial: sc16is7xx: use KBUILD_MODNAME Hugo Villeneuve
2025-10-02 14:57 ` [PATCH v2 13/15] serial: sc16is7xx: change conditional operator indentation Hugo Villeneuve
2025-10-02 14:57 ` [PATCH v2 14/15] serial: sc16is7xx: reformat comments to improve readability Hugo Villeneuve
2025-10-02 14:57 ` [PATCH v2 15/15] serial: sc16is7xx: add comments for lock requirements Hugo Villeneuve
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