Re: [PATCH v5 2/2] mtd: rawnand: meson: add support for Amlogic NAND flash controller

[Liang Yang]

On 2018/10/19 4:39, Boris Brezillon wrote:
> On Thu, 18 Oct 2018 13:09:05 +0800
> Jianxin Pan <jianxin.pan@xxxxxxxxxxx> 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;
> > +}
>
> .