linux-kernel - Re: [PATCH] clk: Add clk_determine

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Message-ID: <f2e54128-f7c1-4193-a511-13775559e261@ti.com>
Date: Wed, 18 Jun 2025 13:37:09 +0530
From: Jayesh Choudhary <j-choudhary@...com>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
CC: <mturquette@...libre.com>, <sboyd@...nel.org>, <linux-clk@...r.kernel.org>,
        <devarsht@...com>, <linux-kernel@...r.kernel.org>,
        <tomi.valkeinen@...asonboard.com>
Subject: Re: [PATCH] clk: Add clk_determine_rate function call

Hello Russell,

Thank you for the review.

On 18/06/25 03:58, Russell King (Oracle) wrote:
> On Mon, Jun 16, 2025 at 04:05:27PM +0530, Jayesh Choudhary wrote:
>> Add a function to determine if a particular rate can be set for a clock
>> with its argument being the clock and the desired rate so that it could
>> be exposed to other peripherals.
>> For example, the display controllers typically has to perform multiple
>> checks for supported display resolutions including those related to
>> clock rates. The controller has to check this way before it actually
>> enables the clock and has to do it multiple times (typically for each
>> mode), and therefore using the clk_set_rate when its not needed, does
>> not make sense.
> 
> So what's up with using clk_round_rate(), which returns the clock rate
> that one would actually get if one calls clk_set_rate() with the the
> value passed into clk_round_rate() ?
> 
> Why is clk_round_rate() not sufficient?
> 

I missed this. Sorry about that. My bad.

In the driver I see that clk_core_determine_round_nolock() will call
determine_rate() op if it is defined. And since clk_round_rate() also
calls this, it is sufficient!!!

I have tested this with my display controller TIDSS on TI's SoC and
have posted that patch upstream:
https://lore.kernel.org/all/20250618075804.139844-1-j-choudhary@ti.com/

This patch is no longer required.

Thanks and Warm Regards,
Jayesh