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Subject: Re: [PATCH v5 2/2] mtd: rawnand: meson: add support for Amlogic NAND
 flash controller
To:     Boris Brezillon <boris.brezillon@bootlin.com>,
        Jianxin Pan <jianxin.pan@amlogic.com>
CC:     <linux-mtd@lists.infradead.org>, Yixun Lan <yixun.lan@amlogic.com>,
        David Woodhouse <dwmw2@infradead.org>,
        Brian Norris <computersforpeace@gmail.com>,
        Marek Vasut <marek.vasut@gmail.com>,
        Richard Weinberger <richard@nod.at>,
        Jerome Brunet <jbrunet@baylibre.com>,
        Neil Armstrong <narmstrong@baylibre.com>,
        Martin Blumenstingl <martin.blumenstingl@googlemail.com>,
        Carlo Caione <carlo@caione.org>,
        Kevin Hilman <khilman@baylibre.com>,
        Rob Herring <robh@kernel.org>, Jian Hu <jian.hu@amlogic.com>,
        Hanjie Lin <hanjie.lin@amlogic.com>,
        Victor Wan <victor.wan@amlogic.com>,
        <linux-amlogic@lists.infradead.org>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-kernel@vger.kernel.org>
References: <1539839345-14021-1-git-send-email-jianxin.pan@amlogic.com>
 <1539839345-14021-3-git-send-email-jianxin.pan@amlogic.com>
 <20181018223943.145e5497@bbrezillon>
From:   Liang Yang <liang.yang@amlogic.com>
Message-ID: <b80f2e72-7ad5-9f37-a059-87b1d8344e7b@amlogic.com>
Date:   Fri, 19 Oct 2018 16:04:09 +0800
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On 2018/10/19 4:39, Boris Brezillon wrote:
> On Thu, 18 Oct 2018 13:09:05 +0800
> Jianxin Pan <jianxin.pan@amlogic.com> wrote:
> 
>> +static int meson_nfc_calc_set_timing(struct meson_nfc *nfc,
>> +				     const struct nand_sdr_timings *timings)
>> +{
>> +	struct nand_timing *timing = &nfc->timing;
>> +	int div, bt_min, bt_max, bus_timing;
>> +	int ret;
>> +
>> +	div = DIV_ROUND_UP((timings->tRC_min / 1000), NFC_CLK_CYCLE);
>> +	ret = clk_set_rate(nfc->device_clk, 1000000000 / div);
>> +	if (ret) {
>> +		dev_err(nfc->dev, "failed to set nand clock rate\n");
>> +		return ret;
>> +	}
>> +
>> +	timing->twb = DIV_ROUND_UP(PSEC_TO_NSEC(timings->tWB_max),
>> +				   div * NFC_CLK_CYCLE);
>> +	timing->tadl = DIV_ROUND_UP(PSEC_TO_NSEC(timings->tADL_min),
>> +				    div * NFC_CLK_CYCLE);
>> +	timing->twhr = DIV_ROUND_UP(PSEC_TO_NSEC(timings->tWHR_min),
>> +				    div * NFC_CLK_CYCLE);
>> +
>> +	bt_min = (timings->tREA_max + NFC_DEFAULT_DELAY) / div;
>> +	bt_max = (NFC_DEFAULT_DELAY + timings->tRHOH_min
>> +			+ timings->tRC_min / 2) / div;
>> +
>> +	bt_min = DIV_ROUND_UP(bt_min, 1000);
>> +	bt_max = DIV_ROUND_UP(bt_max, 1000);
>> +
>> +	if (bt_max < bt_min)
>> +		return -EINVAL;
>> +
>> +	bus_timing = (bt_min + bt_max) / 2 + 1;
>> +
>> +	writel((1 << 21), nfc->reg_base + NFC_REG_CFG);
>> +	writel((NFC_CLK_CYCLE - 1) | (bus_timing << 5),
>> +	       nfc->reg_base + NFC_REG_CFG);
>> +
>> +	writel((1 << 31), nfc->reg_base + NFC_REG_CMD);
>> +
>> +	return 0;
>> +}
>> +
>> +static int
>> +meson_nfc_setup_data_interface(struct nand_chip *nand, int csline,
>> +			       const struct nand_data_interface *conf)
>> +{
>> +	struct meson_nfc *nfc = nand_get_controller_data(nand);
>> +	const struct nand_sdr_timings *timings;
>> +
>> +	timings = nand_get_sdr_timings(conf);
>> +	if (IS_ERR(timings))
>> +		return -ENOTSUPP;
>> +
>> +	if (csline == NAND_DATA_IFACE_CHECK_ONLY)
>> +		return 0;
> 
> Hm, before saying you supporting the requested timing, you should make
> sure they are actually supported. I'd recommend splitting this in 2
> steps:
> 
> 1/ calc timings
> 2/ store the timings in the chip priv struct so that they can be
> applied next time ->select_chip() is called.
> 
ok, i will try to split.

>> +
>> +	meson_nfc_calc_set_timing(nfc, timings);
> > You should not set the timing from ->setup_data_interface(), just
> calculate them, make sure they are supported and store the state in the
> private chip struct. Applying those timings should be done in
> ->select_chip(), so that you can support 2 chips with different timings.
> 
em, i will fix it.
>> +	return 0;
>> +}
> 
> .
>