linux-kernel - Re: [PATCH] i2c: designware: Fix functionality in !CONFIG

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Message-ID: <20200623084530.GO2428291@smile.fi.intel.com>
Date:   Tue, 23 Jun 2020 11:45:30 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Jarkko Nikula <jarkko.nikula@...ux.intel.com>
Cc:     John Stultz <john.stultz@...aro.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Wolfram Sang <wsa@...nel.org>, linux-i2c@...r.kernel.org
Subject: Re: [PATCH] i2c: designware: Fix functionality in !CONFIG_ACPI case

On Tue, Jun 23, 2020 at 10:59:40AM +0300, Jarkko Nikula wrote:
> Hi
> 
> On 6/23/20 5:51 AM, John Stultz wrote:
> > On the HiKey board, where CONFIG_ACPI is not set, we started
> > to see a graphics regression where the adv7511 HDMI bridge driver
> > wasn't probing. This was due to the i2c bus failing to start up.
> > 
> > I bisected the problem down to commit f9288fcc5c615 ("i2c:
> > designware: Move ACPI parts into common module") and after
> > looking at it a bit, I realized that change moved some
> > initialization into i2c_dw_acpi_adjust_bus_speed(). However,
> > i2c_dw_acpi_adjust_bus_speed() is only functional if CONFIG_ACPI
> > is set.
> > 
> > This patch pulls i2c_dw_acpi_adjust_bus_speed() out of the
> > ifdef CONFIG_ACPI conditional, and gets the board working again.
> > 
> > Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> > Cc: Jarkko Nikula <jarkko.nikula@...ux.intel.com>
> > Cc: Wolfram Sang <wsa@...nel.org>
> > Cc: linux-i2c@...r.kernel.org
> > Fixes: f9288fcc5c615 ("i2c: designware: Move ACPI parts into common module")
> > Signed-off-by: John Stultz <john.stultz@...aro.org>
> > ---
> >   drivers/i2c/busses/i2c-designware-common.c | 4 ++--
> >   drivers/i2c/busses/i2c-designware-core.h   | 3 +--
> >   2 files changed, 3 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/i2c/busses/i2c-designware-common.c b/drivers/i2c/busses/i2c-designware-common.c
> > index e3a8640db7da..33de185e15f2 100644
> > --- a/drivers/i2c/busses/i2c-designware-common.c
> > +++ b/drivers/i2c/busses/i2c-designware-common.c
> > @@ -286,6 +286,8 @@ int i2c_dw_acpi_configure(struct device *device)
> >   }
> >   EXPORT_SYMBOL_GPL(i2c_dw_acpi_configure);
> > +#endif	/* CONFIG_ACPI */
> > +
> 
> I think the regression is in these lines below that were moved from probe to
> i2c_dw_acpi_adjust_bus_speed() and cause that neither "cloock-frequency"
> device property or I2C_MAX_FAST_MODE_FREQ affect the bus speed when
> CONFIG_ACPI is not set.
> 
> +       /*
> +        * Find bus speed from the "clock-frequency" device property, ACPI
> +        * or by using fast mode if neither is set.
> +        */
> +       if (acpi_speed && t->bus_freq_hz)
> +               t->bus_freq_hz = min(t->bus_freq_hz, acpi_speed);
> +       else if (acpi_speed || t->bus_freq_hz)
> +               t->bus_freq_hz = max(t->bus_freq_hz, acpi_speed);
> +       else
> +               t->bus_freq_hz = I2C_MAX_FAST_MODE_FREQ;
> 
> Andy: what you think should the i2c_dw_acpi_adjust_bus_speed() fixed to
> return adjusted speed or zero if not found (also for !CONFIG_ACPI) and move
> above lines back to probe? It looks more clear to me that way and should fix
> the regression I think.

I have split it to two functions and renamed accordingly. Will send patch soon,
after some testing.

-- 
With Best Regards,
Andy Shevchenko