linux-kernel - Re: [RFC PATCH 3/4] mtd: rawnand: gpmi: fix controller timings setting

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Date:   Wed, 22 Dec 2021 17:10:29 +0100
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Dario Binacchi <dario.binacchi@...rulasolutions.com>
Cc:     linux-kernel@...r.kernel.org,
        Michael Trimarchi <michael@...rulasolutions.com>,
        Boris Brezillon <bbrezillon@...nel.org>,
        Han Xu <han.xu@....com>, Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-mtd@...ts.infradead.org
Subject: Re: [RFC PATCH 3/4] mtd: rawnand: gpmi: fix controller timings
 setting

Hi Dario,

dario.binacchi@...rulasolutions.com wrote on Fri, 17 Dec 2021 16:55:11
+0100:

> The controller registers are now set accordling to the real clock rate.

You should use another tense (which I forgot the name) such as:

Set the controller registers according to the real clock rate.

But most importantly, you should explain why and perhaps give examples
of frequencies on your setup.

> Fixes: b1206122069a ("mtd: rawnand: gpmi: use core timings instead of an empirical derivation")
> Signed-off-by: Dario Binacchi <dario.binacchi@...rulasolutions.com>
> Co-developed-by: Michael Trimarchi <michael@...rulasolutions.com>
> ---
> 
>  drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c b/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c
> index fd935e893daf..0517b81bb24c 100644
> --- a/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c
> +++ b/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c
> @@ -648,6 +648,7 @@ static void gpmi_nfc_compute_timings(struct gpmi_nand_data *this,
>  				     const struct nand_sdr_timings *sdr)
>  {
>  	struct gpmi_nfc_hardware_timing *hw = &this->hw;
> +	struct resources *r = &this->resources;
>  	unsigned int dll_threshold_ps = this->devdata->max_chain_delay;
>  	unsigned int period_ps, reference_period_ps;
>  	unsigned int data_setup_cycles, data_hold_cycles, addr_setup_cycles;
> @@ -671,6 +672,8 @@ static void gpmi_nfc_compute_timings(struct gpmi_nand_data *this,
>  		wrn_dly_sel = BV_GPMI_CTRL1_WRN_DLY_SEL_NO_DELAY;
>  	}
>  
> +	hw->clk_rate = clk_round_rate(r->clock[0], hw->clk_rate);
> +
>  	/* SDR core timings are given in picoseconds */
>  	period_ps = div_u64((u64)NSEC_PER_SEC * 1000, hw->clk_rate);
>  


Thanks,
Miquèl