* [PATCH] clk: tegra: Fix an infinite loop when clock rate is zero
@ 2018-09-21 22:00 ryang
2018-09-24 8:06 ` Peter De Schrijver
` (2 more replies)
0 siblings, 3 replies; 5+ messages in thread
From: ryang @ 2018-09-21 22:00 UTC (permalink / raw)
To: Peter De Schrijver
Cc: Prashant Gaikwad, Michael Turquette, Stephen Boyd,
Thierry Reding, Jonathan Hunter, linux-clk, linux-tegra,
linux-kernel, ryang
Calling clk_set_rate or clk_round_rate will lock up the kernel when the
rate is zero. This avoids the infinite loop and uses a slightly more
optimized p divider calculation.
Signed-off-by: ryang <decatf@gmail.com>
---
drivers/clk/tegra/clk-pll.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/drivers/clk/tegra/clk-pll.c b/drivers/clk/tegra/clk-pll.c
index 830d1c87fa7c..17a058c3bbc1 100644
--- a/drivers/clk/tegra/clk-pll.c
+++ b/drivers/clk/tegra/clk-pll.c
@@ -582,9 +582,8 @@ static int _calc_rate(struct clk_hw *hw, struct tegra_clk_pll_freq_table *cfg,
}
/* Raise VCO to guarantee 0.5% accuracy */
- for (cfg->output_rate = rate; cfg->output_rate < 200 * cfreq;
- cfg->output_rate <<= 1)
- p_div++;
+ p_div = rate ? fls((200 * cfreq) / rate) : 0;
+ cfg->output_rate = rate << p_div;
cfg->m = parent_rate / cfreq;
cfg->n = cfg->output_rate / cfreq;
--
2.17.1
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] clk: tegra: Fix an infinite loop when clock rate is zero
2018-09-21 22:00 [PATCH] clk: tegra: Fix an infinite loop when clock rate is zero ryang
@ 2018-09-24 8:06 ` Peter De Schrijver
2018-09-24 11:40 ` Thierry Reding
2018-10-01 22:08 ` Stephen Boyd
2 siblings, 0 replies; 5+ messages in thread
From: Peter De Schrijver @ 2018-09-24 8:06 UTC (permalink / raw)
To: ryang
Cc: Prashant Gaikwad, Michael Turquette, Stephen Boyd,
Thierry Reding, Jonathan Hunter, linux-clk, linux-tegra,
linux-kernel
On Fri, Sep 21, 2018 at 06:00:37PM -0400, ryang wrote:
> Calling clk_set_rate or clk_round_rate will lock up the kernel when the
> rate is zero. This avoids the infinite loop and uses a slightly more
> optimized p divider calculation.
>
Acked-By: Peter De Schrijver <pdeschrijver@nvidia.com>
At some point we should also limit pdiv to its maximum possible value, but
that's not so obvious as we need to take into account PLLs where pdiv is
non-linear.
Peter.
> Signed-off-by: ryang <decatf@gmail.com>
> ---
> drivers/clk/tegra/clk-pll.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/clk/tegra/clk-pll.c b/drivers/clk/tegra/clk-pll.c
> index 830d1c87fa7c..17a058c3bbc1 100644
> --- a/drivers/clk/tegra/clk-pll.c
> +++ b/drivers/clk/tegra/clk-pll.c
> @@ -582,9 +582,8 @@ static int _calc_rate(struct clk_hw *hw, struct tegra_clk_pll_freq_table *cfg,
> }
>
> /* Raise VCO to guarantee 0.5% accuracy */
> - for (cfg->output_rate = rate; cfg->output_rate < 200 * cfreq;
> - cfg->output_rate <<= 1)
> - p_div++;
> + p_div = rate ? fls((200 * cfreq) / rate) : 0;
> + cfg->output_rate = rate << p_div;
>
> cfg->m = parent_rate / cfreq;
> cfg->n = cfg->output_rate / cfreq;
> --
> 2.17.1
>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] clk: tegra: Fix an infinite loop when clock rate is zero
2018-09-21 22:00 [PATCH] clk: tegra: Fix an infinite loop when clock rate is zero ryang
2018-09-24 8:06 ` Peter De Schrijver
@ 2018-09-24 11:40 ` Thierry Reding
2018-10-01 22:08 ` Stephen Boyd
2 siblings, 0 replies; 5+ messages in thread
From: Thierry Reding @ 2018-09-24 11:40 UTC (permalink / raw)
To: ryang
Cc: Peter De Schrijver, Prashant Gaikwad, Michael Turquette,
Stephen Boyd, Jonathan Hunter, linux-clk, linux-tegra,
linux-kernel
[-- Attachment #1: Type: text/plain, Size: 436 bytes --]
On Fri, Sep 21, 2018 at 06:00:37PM -0400, ryang wrote:
> Calling clk_set_rate or clk_round_rate will lock up the kernel when the
> rate is zero. This avoids the infinite loop and uses a slightly more
> optimized p divider calculation.
>
> Signed-off-by: ryang <decatf@gmail.com>
> ---
> drivers/clk/tegra/clk-pll.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
Acked-by: Thierry Reding <treding@nvidia.com>
[-- Attachment #2: signature.asc --]
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] clk: tegra: Fix an infinite loop when clock rate is zero
2018-09-21 22:00 [PATCH] clk: tegra: Fix an infinite loop when clock rate is zero ryang
2018-09-24 8:06 ` Peter De Schrijver
2018-09-24 11:40 ` Thierry Reding
@ 2018-10-01 22:08 ` Stephen Boyd
2018-10-02 7:35 ` Stephen Boyd
2 siblings, 1 reply; 5+ messages in thread
From: Stephen Boyd @ 2018-10-01 22:08 UTC (permalink / raw)
To: Peter De Schrijver, ryang
Cc: Prashant Gaikwad, Michael Turquette, Thierry Reding,
Jonathan Hunter, linux-clk, linux-tegra, linux-kernel, ryang
Quoting ryang (2018-09-21 15:00:37)
> Calling clk_set_rate or clk_round_rate will lock up the kernel when the
> rate is zero. This avoids the infinite loop and uses a slightly more
> optimized p divider calculation.
>
> Signed-off-by: ryang <decatf@gmail.com>
Do you have a more proper name? Or you want the author name to show up as
"ryang"?
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] clk: tegra: Fix an infinite loop when clock rate is zero
2018-10-01 22:08 ` Stephen Boyd
@ 2018-10-02 7:35 ` Stephen Boyd
0 siblings, 0 replies; 5+ messages in thread
From: Stephen Boyd @ 2018-10-02 7:35 UTC (permalink / raw)
To: Peter De Schrijver, ryang
Cc: Prashant Gaikwad, Michael Turquette, Thierry Reding,
Jonathan Hunter, linux-clk, linux-tegra, linux-kernel, ryang
Quoting Stephen Boyd (2018-10-01 15:08:46)
> Quoting ryang (2018-09-21 15:00:37)
> > Calling clk_set_rate or clk_round_rate will lock up the kernel when the
> > rate is zero. This avoids the infinite loop and uses a slightly more
> > optimized p divider calculation.
> >
> > Signed-off-by: ryang <decatf@gmail.com>
>
> Do you have a more proper name? Or you want the author name to show up as
> "ryang"?
>
I see a v2 on the list, and it looks similar so I'm going to assume this
is superseded now.
^ permalink raw reply [flat|nested] 5+ messages in thread
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2018-09-21 22:00 [PATCH] clk: tegra: Fix an infinite loop when clock rate is zero ryang
2018-09-24 8:06 ` Peter De Schrijver
2018-09-24 11:40 ` Thierry Reding
2018-10-01 22:08 ` Stephen Boyd
2018-10-02 7:35 ` Stephen Boyd
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