linux-kernel - Re: [PATCH 11/19] clk: at91: clk-generated: pass the id of changeable parent at registration

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Date:   Thu, 16 Jul 2020 16:57:18 +0000
From:   <Codrin.Ciubotariu@...rochip.com>
To:     <Claudiu.Beznea@...rochip.com>, <mturquette@...libre.com>,
        <sboyd@...nel.org>, <Nicolas.Ferre@...rochip.com>,
        <alexandre.belloni@...tlin.com>, <Ludovic.Desroches@...rochip.com>
CC:     <bbrezillon@...nel.org>, <linux-kernel@...r.kernel.org>,
        <linux-clk@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 11/19] clk: at91: clk-generated: pass the id of changeable
 parent at registration

Hi Claudiu,

On 15.07.2020 14:24, Claudiu Beznea wrote:
> Pass the ID of changeable parent at registration. This will allow
> the scalability of this clock driver with regards to the changeable
> parent ID for versions of this IP where changeable parent is not the
> last one in the parents list (e.g. SAMA7G5). In
> clk_generated_best_diff() the *best_diff variable is check against
> tmp_diff variable using ">=" operator instead of ">" so that in case
> the requested frequency could be obtained using fix parents + gck
> dividers but the clock also supports changeable parent to be able
> to force the usage of the changeable parent.

This is a great feature!

> 
> Signed-off-by: Claudiu Beznea <claudiu.beznea@...rochip.com>
> ---
>   drivers/clk/at91/clk-generated.c | 26 ++++++++++++++------------
>   drivers/clk/at91/dt-compat.c     |  8 +++++---
>   drivers/clk/at91/pmc.h           |  4 ++--
>   drivers/clk/at91/sam9x60.c       |  3 +--
>   drivers/clk/at91/sama5d2.c       | 31 +++++++++++++++----------------
>   5 files changed, 37 insertions(+), 35 deletions(-)
> 
> diff --git a/drivers/clk/at91/clk-generated.c b/drivers/clk/at91/clk-generated.c
> index 2448bdc63425..f9ca04c97128 100644
> --- a/drivers/clk/at91/clk-generated.c
> +++ b/drivers/clk/at91/clk-generated.c
> @@ -18,8 +18,6 @@
>   
>   #define GENERATED_MAX_DIV	255
>   
> -#define GCK_INDEX_DT_AUDIO_PLL	5
> -
>   struct clk_generated {
>   	struct clk_hw hw;
>   	struct regmap *regmap;
> @@ -29,7 +27,7 @@ struct clk_generated {
>   	u32 gckdiv;
>   	const struct clk_pcr_layout *layout;
>   	u8 parent_id;
> -	bool audio_pll_allowed;
> +	int chg_pid;
>   };
>   
>   #define to_clk_generated(hw) \
> @@ -109,7 +107,7 @@ static void clk_generated_best_diff(struct clk_rate_request *req,
>   		tmp_rate = parent_rate / div;
>   	tmp_diff = abs(req->rate - tmp_rate);
>   
> -	if (*best_diff < 0 || *best_diff > tmp_diff) {
> +	if (*best_diff < 0 || *best_diff >= tmp_diff) {
>   		*best_rate = tmp_rate;
>   		*best_diff = tmp_diff;
>   		req->best_parent_rate = parent_rate;
> @@ -129,7 +127,10 @@ static int clk_generated_determine_rate(struct clk_hw *hw,
>   	int i;
>   	u32 div;
>   
> -	for (i = 0; i < clk_hw_get_num_parents(hw) - 1; i++) {
> +	for (i = 0; i < clk_hw_get_num_parents(hw); i++) {
> +		if (gck->chg_pid == i)
> +			continue;
> +

One thing that the previous loop was preventing was to not allow other 
gcks take clk_hw_get_num_parents(hw) - 1 as a parent. So the audio pll 
(last one) was reserved for the gck of the audio peripherals only. With 
this change, any peripheral can use chg_pid as a parent, preventing thus 
its correct use by the peripherals that can actually need and change the 
rate of chg_pid.

>   		parent = clk_hw_get_parent_by_index(hw, i);
>   		if (!parent)
>   			continue;
> @@ -161,10 +162,10 @@ static int clk_generated_determine_rate(struct clk_hw *hw,
>   	 * that the only clks able to modify gck rate are those of audio IPs.
>   	 */

The above comment should be updated.

>   
> -	if (!gck->audio_pll_allowed)
> +	if (gck->chg_pid < 0)
>   		goto end;

Best regards,
Codrin