Re: [PATCH v2] i2c: sh_mobile: Switch R-Mobile A1/APE6 and SH-Mobile AG5 to new frequency calculation

Wolfram Sang <[email protected]> Wed, 31 Jan 2024 21:34:56 +0100

Newsgroups	gmane.linux.drivers.i2c,gmane.linux.kernel.renesas-soc,gmane.linux.ports.sh.devel
Message-ID	<Zbqu8K3gBth83YBV@shikoro>

On Wed, Jan 31, 2024 at 05:09:30PM +0100, Geert Uytterhoeven wrote:
> Switch the R-Mobile A1, R-Mobile APE6, and SH-Mobile AG5 SoCs to the new
> frequency calculation formula, to (a) avoid running the I2C bus too fast,
> and (b) bring the low/high ratio closer to the recommended ratio 5/4.
> 
> As this makes fast_clock_dt_config and v2_freq_calc_dt_config identical,
> merge them into a single fast_clock_dt_config.
> 
> Legacy SH users (sh7343, sh7366, and sh772[234]) are left alone, and
> still use the old formula.
> 
> Measurement results on R-Mobile APE6 and SH-Mobile AG5 (fck=104 MHz,
> clks_per_count=2):
>   100 kHz: 106 kHz LH=1.12 before, 99.6 kHz L/H=1.22 after
>   400 kHz: 384 kHz LH=1.67 before, 392 kHz L/H=1.27 after
> 
> Measurement results on R-Mobile A1 (fck=49.5 MHz, clks_per_count=1):
>   100 kHz: 106 kHz L/H=1.09 before, 99.6 kHz L/H=1.20 after
> 
> Signed-off-by: Geert Uytterhoeven <[email protected]>

Reviewed-by: Wolfram Sang <[email protected]>

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