Re: [PATCH 1/3] drm/tegra: vic: Implement explicit reset support

[Thierry Reding <thierry.reding@gmail.com>]

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On Thu, Nov 29, 2018 at 01:40:32PM +0000, Jon Hunter wrote:
> 
> On 23/11/2018 12:06, Thierry Reding wrote:
> > From: Thierry Reding <treding@nvidia.com>
> > 
> > Tegra supports generic PM domains on 64-bit ARM, and if that is enabled,
> > the power domain code will make sure that resets are asserted and
> > deasserted at appropriate points in time.
> > 
> > If generic PM domains are not implemented, such as on 32-bit Tegra, the
> > resets need to be asserted and deasserted explicitly by the driver.
> > 
> > Signed-off-by: Thierry Reding <treding@nvidia.com>
> > ---
> >  drivers/gpu/drm/tegra/vic.c | 35 ++++++++++++++++++++++++++++++++++-
> >  1 file changed, 34 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/tegra/vic.c b/drivers/gpu/drm/tegra/vic.c
> > index 9fa77405db01..23f530db45ad 100644
> > --- a/drivers/gpu/drm/tegra/vic.c
> > +++ b/drivers/gpu/drm/tegra/vic.c
> > @@ -38,6 +38,7 @@ struct vic {
> >  	struct iommu_domain *domain;
> >  	struct device *dev;
> >  	struct clk *clk;
> > +	struct reset_control *rst;
> >  
> >  	/* Platform configuration */
> >  	const struct vic_config *config;
> > @@ -56,13 +57,37 @@ static void vic_writel(struct vic *vic, u32 value, unsigned int offset)
> >  static int vic_runtime_resume(struct device *dev)
> >  {
> >  	struct vic *vic = dev_get_drvdata(dev);
> > +	int err;
> > +
> > +	err = clk_prepare_enable(vic->clk);
> > +	if (err < 0)
> > +		return err;
> > +
> > +	usleep_range(2000, 4000);
> 
> The Tegra genpd code has a usleep_range(10, 20), is that not sufficient
> here? If it is, it would be good to be consistent.

Yeah, I think that's enough. The Tegra DRM driver uses these ranges in
many places, so that's where I copied them from. None of these are part
of a hot path or anything, so whether this sleeps for 10 ns or 4 ms is
not going to matter much.

With that changed, can I consider this R-b you?

Thierry

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