Re: [PATCH v11 7/7] drm/lsdc: add drm driver for loongson display controller

[Sui Jingfeng]

On 2022/3/23 04:49, Rob Herring wrote:
> > +/*
> > + * ls7a_gpio_i2c_set - set the state of a gpio pin indicated by mask
> > + * @mask: gpio pin mask
> > + */
> > +static void ls7a_gpio_i2c_set(struct lsdc_i2c * const li2c, int mask, int state)
> > +{
> > +	unsigned long flags;
> > +	u8 val;
> > +
> > +	spin_lock_irqsave(&li2c->reglock, flags);
> What are you protecting? Doesn't the caller serialize calls to these
> functions?
This driver is ported from my work from my downstream work.

Maxime also ask this question before, but i did not answer.
He is right, protect single register access is not necessary.
uncached access have done the job itself.
so i remove it in V11 of my patch set.

There are two way GPIO emulated i2c, I want the code between
spin_lock_irqsave(&li2c->reglock, flags) and spin_unlock_irqrestore(&li2c->reglock, flags);
finished in a atomic way, without any disruption.

The two i2c should not have any influence each other.
I write it by gut feeling, and luckily it works very well in practice.