linux-kernel - Re: [PATCH 1/2] reset-controller: ti: adjust the reset assert and deassert interface

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Message-ID: <d259a74ca9e425f9b39ebbf47b0decb6be0beed5.camel@pengutronix.de>
Date:   Wed, 29 Jul 2020 10:02:16 +0200
From:   Philipp Zabel <p.zabel@...gutronix.de>
To:     Matthias Brugger <matthias.bgg@...il.com>,
        Crystal Guo <crystal.guo@...iatek.com>, robh+dt@...nel.org
Cc:     srv_heupstream@...iatek.com, linux-mediatek@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, seiya.wang@...iatek.com
Subject: Re: [PATCH 1/2] reset-controller: ti: adjust the reset assert and
 deassert interface

Hi Crystal, Matthias,

On Wed, 2020-07-29 at 09:48 +0200, Matthias Brugger wrote:
> 
> On 29/07/2020 09:39, Crystal Guo wrote:
> > Add ti_syscon_reset() to integrate assert and deassert together,
> > and change return value of the reset assert and deassert interface
> > from regmap_update_bits to regmap_write_bits.
> > 
> > when clear bit is already 1, regmap_update_bits can not write 1 to it again.
> > Some IC has the feature that, when set bit is 1, the clear bit change
> > to 1 together. It will truly clear bit to 0 by write 1 to the clear bit
> > 
> > Signed-off-by: Crystal Guo <crystal.guo@...iatek.com>
> > ---
> >   drivers/reset/reset-ti-syscon.c | 13 +++++++++++--
> >   1 file changed, 11 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/reset/reset-ti-syscon.c b/drivers/reset/reset-ti-syscon.c
> > index a2635c2..5a8ec8f 100644
> > --- a/drivers/reset/reset-ti-syscon.c
> > +++ b/drivers/reset/reset-ti-syscon.c
> > @@ -89,7 +89,7 @@ static int ti_syscon_reset_assert(struct reset_controller_dev *rcdev,
> >   	mask = BIT(control->assert_bit);
> >   	value = (control->flags & ASSERT_SET) ? mask : 0x0;
> >   
> > -	return regmap_update_bits(data->regmap, control->assert_offset, mask, value);
> > +	return regmap_write_bits(data->regmap, control->assert_offset, mask, value);
> 
> Nack, this will break the driver for the other devices.

I don't think this will break the driver for existing hardware.
regmap_write_bits() is the same as regmap_update_bits(), it just forces
the write in case the read already happens to return the correct value.
Of course it would be good to check that this actually works.

> The kernel has to work not just for your SoC but for all devices of all 
> architectures. You can't just hack something up, that will work on your specific 
> SoC.
> 
> Regards,
> Matthias
> 
> >   }
> >   
> >   /**
> > @@ -120,7 +120,7 @@ static int ti_syscon_reset_deassert(struct reset_controller_dev *rcdev,
> >   	mask = BIT(control->deassert_bit);
> >   	value = (control->flags & DEASSERT_SET) ? mask : 0x0;
> >   
> > -	return regmap_update_bits(data->regmap, control->deassert_offset, mask, value);
> > +	return regmap_write_bits(data->regmap, control->deassert_offset, mask, value);
> >   }
> >   
> >   /**
> > @@ -158,10 +158,19 @@ static int ti_syscon_reset_status(struct reset_controller_dev *rcdev,
> >   		!(control->flags & STATUS_SET);
> >   }
> >   
> > +static int ti_syscon_reset(struct reset_controller_dev *rcdev,
> > +			   unsigned long id)
> > +{
> > +	ti_syscon_reset_assert(rcdev, id);
> > +
> > +	return ti_syscon_reset_deassert(rcdev, id);
> > +}
> > +

I'm unsure about this one, though. This is an incompatible change. At
the very least this would have to be optional depending on compatible.

regards
Philipp