linux-kernel - Re: [PATCH v4] i2c: spacemit: configure ILCR for accurate SCL frequency

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Message-ID: <748544ABF6A72D31+aPg31PBvHDkBALoa@kernel.org>
Date: Wed, 22 Oct 2025 09:48:04 +0800
From: Troy Mitchell <troy.mitchell@...ux.spacemit.com>
To: Andi Shyti <andi.shyti@...nel.org>,
	Troy Mitchell <troy.mitchell@...ux.spacemit.com>
Cc: Yixun Lan <dlan@...too.org>, linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org,
	spacemit@...ts.linux.dev
Subject: Re: [PATCH v4] i2c: spacemit: configure ILCR for accurate SCL
 frequency

Hi Andi,
On Tue, Oct 21, 2025 at 06:03:34PM +0200, Andi Shyti wrote:
> Hi Troy,
> 
> On Mon, Oct 20, 2025 at 11:28:45AM +0200, Andi Shyti wrote:
> > On Fri, Oct 17, 2025 at 03:27:39PM +0800, Troy Mitchell wrote:
> > > The SpacemiT I2C controller's SCL (Serial Clock Line) frequency for
> > > master mode operations is determined by the ILCR (I2C Load Count Register).
> > > Previously, the driver relied on the hardware's reset default
> > > values for this register.
> > > 
> > > The hardware's default ILCR values (SLV=0x156, FLV=0x5d) yield SCL
> > > frequencies lower than intended. For example, with the default
> > > 31.5 MHz input clock, these default settings result in an SCL
> > > frequency of approximately 93 kHz (standard mode) when targeting 100 kHz,
> > > and approximately 338 kHz (fast mode) when targeting 400 kHz.
> > > These frequencies are below the 100 kHz/400 kHz nominal speeds.
> > > 
> > > This patch integrates the SCL frequency management into
> > > the Common Clock Framework (CCF). Specifically, the ILCR register,
> > > which acts as a frequency divider for the SCL clock, is now registered
> > > as a managed clock (scl_clk) within the CCF.
> > > 
> > > This patch also cleans up unnecessary whitespace
> > > in the included header files.
> > > 
> > > Signed-off-by: Troy Mitchell <troy.mitchell@...ux.spacemit.com>
> > 
> > merged to i2c/i2c-host.
> 
> I'm sorry, because of the report from LKP(*) I reverted your
> patch. I2C_K1 is selected by MFD_SPACEMIT_P1, so that we get the
> following warning:
> 
>   WARNING: unmet direct dependencies detected for I2C_K1
> 
> and compile I2C_K1 without COMMON_CLK. Please, fix it and
> resubmit the patch.
Yes, I noticed that too. The issue is introduced by PMIC driver(P1)
instead of I2C.
Should I resubmit this patch right after sending the fix,
or wait until the fix gets merged first?

                                - Troy
> 
> Thanks,
> Andi
> 
> (*) https://lore.kernel.org/oe-kbuild-all/202510202150.2qXd8e7Y-lkp@intel.com/
>