From: Nicolas Ferre <nicolas.ferre@microchip.com>
To: Codrin Ciubotariu - M19940 <Codrin.Ciubotariu@microchip.com>,
"linux-clk@vger.kernel.org" <linux-clk@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc: "mturquette@baylibre.com" <mturquette@baylibre.com>,
"sboyd@kernel.org" <sboyd@kernel.org>,
"alexandre.belloni@bootlin.com" <alexandre.belloni@bootlin.com>,
Ludovic Desroches - M43218 <Ludovic.Desroches@microchip.com>,
Claudiu Beznea - M18063 <Claudiu.Beznea@microchip.com>
Subject: Re: [PATCH] clk: at91: clk-generated: Limit the requested rate to our range
Date: Fri, 16 Jul 2021 21:17:06 +0200 [thread overview]
Message-ID: <4393ec64-3891-a875-b948-516efd08817c@microchip.com> (raw)
In-Reply-To: <25631072-d9a3-0d84-fd47-4d2414f079f6@microchip.com>
On 09/07/2021 at 11:59, Codrin Ciubotariu - M19940 wrote:
> On 09.07.2021 12:21, Nicolas Ferre wrote:
>> On 07/07/2021 at 15:12, Codrin Ciubotariu wrote:
>>> On clk_generated_determine_rate(), the requested rate could be outside
>>> of clk's range. Limit the rate to the clock's range to not return an
>>> error.
>>
>> Isn't it saner for the user to return an error code instead of
>> automatically restrain the dynamics requested without notice?
>>
>> Can you elaborate the use case where returning an error is not convenient?
>
> The way I see it, if the user requests a rate that is out of clock's
> range, the driver's determine_rate() should return min/max, not an
> error. That is actually the closest rate supported by the clock, which
> is what determine_rate() should accomplish. The user has no clk API to
> get clock's range, so there is no way to call clk_round_rate() only for
> values within our range.
>
> The use cause is with sam9x60's I2S driver, which has to try different
> rates to get the closest one to what it needs. There is no 'perfect'
> rate, because there is no AUDIO PLL and we have to try different values
> for our internal dividers to find the closest one.
>
> https://elixir.bootlin.com/linux/latest/source/sound/soc/atmel/mchp-i2s-mcc.c#L416
Sure, makes sense:
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Regards,
Nicolas
--
Nicolas Ferre
next prev parent reply other threads:[~2021-07-16 19:17 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-07 13:12 [PATCH] clk: at91: clk-generated: Limit the requested rate to our range Codrin Ciubotariu
2021-07-09 9:21 ` Nicolas Ferre
2021-07-09 9:59 ` Codrin.Ciubotariu
2021-07-16 19:17 ` Nicolas Ferre [this message]
2021-08-29 5:28 ` Stephen Boyd
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