From: Elaine Zhang <zhangqing@rock-chips.com>
To: Heiko Stuebner <heiko@sntech.de>,
mturquette@baylibre.com, sboyd@codeaurora.org
Cc: linux-clk@vger.kernel.org, linux-rockchip@lists.infradead.org,
zhengxing@rock-chips.com, tomeu.vizoso@collabora.com
Subject: Re: [RFC PATCH 2/3] clk: adjust clocks to their requested rate after parent changes
Date: Tue, 05 Jul 2016 15:27:30 +0800 [thread overview]
Message-ID: <577B6162.3020609@rock-chips.com> (raw)
In-Reply-To: <1462206982-10444-3-git-send-email-heiko@sntech.de>
On 05/03/2016 12:36 AM, Heiko Stuebner wrote:
> Given a hirarchy of clk1 -> [div] -> clk2, when the rate of clk1 gets
> changed, clk2 changes as well as the divider stays the same. There may
> be cases where a user of clk2 needs it at a specific rate, so clk2
> needs to be readjusted for the changed rate of clk1.
>
> So if a rate was requested for the clock, and its rate changed during
> the underlying rate-change, with this change the clock framework now
> tries to readjust the rate back to/near the requested one.
>
> The whole process is protected by a new clock-flag to not force this
> behaviour change onto every clock defined in the ccf.
>
> Signed-off-by: Heiko Stuebner <heiko@sntech.de>
> ---
> drivers/clk/clk.c | 13 +++++++++++--
> include/linux/clk-provider.h | 1 +
> 2 files changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index 65e0aad..22be369 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -1410,6 +1410,9 @@ static struct clk_core *clk_propagate_rate_change(struct clk_core *core,
> return fail_clk;
> }
>
> +static int clk_core_set_rate_nolock(struct clk_core *core,
> + unsigned long req_rate);
> +
> /*
> * walk down a subtree and set the new rates notifying the rate
> * change on the way
> @@ -1494,6 +1497,12 @@ static void clk_change_rate(struct clk_core *core)
> /* handle the new child who might not be in core->children yet */
> if (core->new_child)
> clk_change_rate(core->new_child);
> +
> + /* handle a changed clock that needs to readjust its rate */
> + if (core->flags & CLK_KEEP_REQ_RATE && core->req_rate
> + && core->new_rate != old_rate
> + && core->new_rate != core->req_rate)
> + clk_core_set_rate_nolock(core, core->req_rate);
> }
I tests found a problem, about set the freq order.
e.p:
[VPLL]
|
------ [div] ----- dclk_vop
If I change VPLL freq 148.5M to 594M, dclk_vop freq will changed as:
148.5M->24M->594M->1485.5M.
But we not hope the dclk_vop have a high freq,it will make the system
crash or make vop not work well.
So if the VPLL is improve the freq, we need to set dclk_vop div first,
and than set VPLL freq.
If VPLL is reduce the freq, we need to set vpll first,and set dclk_vop div.
This is just a example,for all change parent freq, we need follow this
operation.
Do you have a better idea for this problem?
>
> static int clk_core_set_rate_nolock(struct clk_core *core,
> @@ -1529,11 +1538,11 @@ static int clk_core_set_rate_nolock(struct clk_core *core,
> return -EBUSY;
> }
>
> + core->req_rate = req_rate;
> +
> /* change the rates */
> clk_change_rate(top);
>
> - core->req_rate = req_rate;
> -
> return ret;
> }
>
> diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
> index 0c72204..06f189e 100644
> --- a/include/linux/clk-provider.h
> +++ b/include/linux/clk-provider.h
> @@ -33,6 +33,7 @@
> #define CLK_RECALC_NEW_RATES BIT(9) /* recalc rates after notifications */
> #define CLK_SET_RATE_UNGATE BIT(10) /* clock needs to run to set rate */
> #define CLK_IS_CRITICAL BIT(11) /* do not gate, ever */
> +#define CLK_KEEP_REQ_RATE BIT(12) /* keep reqrate on parent rate change */
>
> struct clk;
> struct clk_hw;
>
next prev parent reply other threads:[~2016-07-05 7:27 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-02 16:36 [RFC PATCH 0/3] clk: attempt to keep requested rate on parent changes Heiko Stuebner
2016-05-02 16:36 ` [RFC PATCH 1/3] clk: fix inconsistent use of req_rate Heiko Stuebner
2016-05-02 16:36 ` [RFC PATCH 2/3] clk: adjust clocks to their requested rate after parent changes Heiko Stuebner
2016-05-06 0:35 ` Doug Anderson
2016-05-06 0:49 ` Doug Anderson
2016-05-08 20:34 ` Heiko Stuebner
2016-05-09 11:40 ` Heiko Stuebner
2016-05-09 15:49 ` Doug Anderson
2016-07-05 7:27 ` Elaine Zhang [this message]
2016-07-05 22:24 ` Heiko Stuebner
2016-07-06 1:39 ` Elaine Zhang
2016-07-06 23:01 ` Doug Anderson
2016-07-06 22:41 ` Doug Anderson
2016-05-02 16:36 ` [RFC PATCH 3/3] clk: rockchip: make rk3399 vop dclks keep their rate on parent rate changes Heiko Stuebner
2016-05-05 13:30 ` [RFC PATCH 0/3] clk: attempt to keep requested rate on parent changes Tomeu Vizoso
2016-05-05 15:07 ` Heiko Stübner
2016-05-06 0:46 ` Doug Anderson
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