Re: [PATCH v4 65/68] clk: tegra: super: Switch to determine_rate

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

[-- Attachment #1: Type: text/plain, Size: 3024 bytes --]

On Tue, Jun 20, 2023 at 12:09:09PM -0700, Stephen Boyd wrote:
> Quoting Maxime Ripard (2023-06-19 00:26:19)
> > On Mon, Jun 19, 2023 at 02:38:59AM +0300, Dmitry Osipenko wrote:
> > > 05.05.2023 14:26, Maxime Ripard пишет:
> > > > 
> > > > diff --git a/drivers/clk/tegra/clk-super.c b/drivers/clk/tegra/clk-super.c
> > > > index 3f3a7a203c5f..7ec47942720c 100644
> > > > --- a/drivers/clk/tegra/clk-super.c
> > > > +++ b/drivers/clk/tegra/clk-super.c
> > > > @@ -142,15 +142,22 @@ static const struct clk_ops tegra_clk_super_mux_ops = {
> > > >     .restore_context = clk_super_mux_restore_context,
> > > >  };
> > > >  
> > > > -static long clk_super_round_rate(struct clk_hw *hw, unsigned long rate,
> > > > -                            unsigned long *parent_rate)
> > > > +static int clk_super_determine_rate(struct clk_hw *hw,
> > > > +                               struct clk_rate_request *req)
> > > >  {
> > > >     struct tegra_clk_super_mux *super = to_clk_super_mux(hw);
> > > >     struct clk_hw *div_hw = &super->frac_div.hw;
> > > > +   unsigned long rate;
> > > >  
> > > >     __clk_hw_set_clk(div_hw, hw);
> > > >  
> > > > -   return super->div_ops->round_rate(div_hw, rate, parent_rate);
> > > > +   rate = super->div_ops->round_rate(div_hw, req->rate,
> > > > +                                     &req->best_parent_rate);
> > > > +   if (rate < 0)
> 
> There's the report that this condition is never possible. Maybe the
> previous code was relying on an error value sometimes. Can we add
> determine_rate to the div_ops and simplify this code? I asked on the
> list for that earlier.

I was able to reproduce this on a Tegra30 Beaver, but the problem is
more straightforward than this. The crash I was seeing during boot was
because cclk_super_determine_rate() was still calling the round_rate()
callback from tegra_clk_super_ops, which this patch removed (and added
determine_rate() instead).

The following fixes the problem for me. It's basically converting the
round_rate() call to an equivalent determine_rate() call.

Dmitry, can you verify that this fixes the issue that you were seeing?

Thierry

--- >8 ---
diff --git a/drivers/clk/tegra/clk-tegra-super-cclk.c b/drivers/clk/tegra/clk-tegra-super-cclk.c
index 68d7bcd5fc8a..8a2bb4ae4fd2 100644
--- a/drivers/clk/tegra/clk-tegra-super-cclk.c
+++ b/drivers/clk/tegra/clk-tegra-super-cclk.c
@@ -86,9 +86,16 @@ static int cclk_super_determine_rate(struct clk_hw *hw,
 	if (rate <= pllp_rate) {
 		if (super->flags & TEGRA20_SUPER_CLK)
 			rate = pllp_rate;
-		else
-			rate = tegra_clk_super_ops.round_rate(hw, rate,
-							      &pllp_rate);
+		else {
+			struct clk_rate_request parent = {
+				.rate = req->rate,
+				.best_parent_rate = pllp_rate,
+			};
+
+			tegra_clk_super_ops.determine_rate(hw, &parent);
+			pllp_rate = parent.best_parent_rate;
+			rate = parent.rate;
+		}
 
 		req->best_parent_rate = pllp_rate;
 		req->best_parent_hw = pllp_hw;
--- >8 ---

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]