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

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Date:   Thu, 18 Oct 2018 16:24:49 +0200
From:   Boris Brezillon <boris.brezillon@...tlin.com>
To:     Jianxin Pan <jianxin.pan@...ogic.com>
Cc:     <linux-mtd@...ts.infradead.org>,
        Liang Yang <liang.yang@...ogic.com>,
        Yixun Lan <yixun.lan@...ogic.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Richard Weinberger <richard@....at>,
        Jerome Brunet <jbrunet@...libre.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Carlo Caione <carlo@...one.org>,
        Kevin Hilman <khilman@...libre.com>,
        Rob Herring <robh@...nel.org>, Jian Hu <jian.hu@...ogic.com>,
        Hanjie Lin <hanjie.lin@...ogic.com>,
        Victor Wan <victor.wan@...ogic.com>,
        <linux-amlogic@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 2/2] mtd: rawnand: meson: add support for Amlogic
 NAND flash controller

On Thu, 18 Oct 2018 13:09:05 +0800
Jianxin Pan <jianxin.pan@...ogic.com> wrote:

> +static int meson_nfc_exec_op(struct nand_chip *chip,
> +			     const struct nand_operation *op, bool check_only)
> +{
> +	struct mtd_info *mtd = nand_to_mtd(chip);
> +	struct meson_nfc *nfc = nand_get_controller_data(chip);
> +	const struct nand_op_instr *instr = NULL;
> +	int ret = 0, cmd;
> +	unsigned int op_id;
> +	int i;
> +
> +	for (op_id = 0; op_id < op->ninstrs; op_id++) {
> +		instr = &op->instrs[op_id];
> +		switch (instr->type) {
> +		case NAND_OP_CMD_INSTR:
> +			if (instr->ctx.cmd.opcode == NAND_CMD_STATUS)
> +				meson_nfc_cmd_idle(nfc, nfc->timing.twb);

Hm, I don't want drivers to base their decisions on the opcode value.
There's a ->delay_ns field in the instruction object, can't you use
that one instead? Also, I don't understand why this is only needed for
the STATUS command. It should normally be applied to all instructions.

> +			cmd = nfc->param.chip_select | NFC_CMD_CLE;
> +			cmd |= instr->ctx.cmd.opcode & 0xff;
> +			writel(cmd, nfc->reg_base + NFC_REG_CMD);
> +			if (instr->ctx.cmd.opcode == NAND_CMD_STATUS)
> +				meson_nfc_cmd_idle(nfc, nfc->timing.twhr);
> +			break;
> +
> +		case NAND_OP_ADDR_INSTR:
> +			for (i = 0; i < instr->ctx.addr.naddrs; i++) {
> +				cmd = nfc->param.chip_select | NFC_CMD_ALE;
> +				cmd |= instr->ctx.addr.addrs[i] & 0xff;
> +				writel(cmd, nfc->reg_base + NFC_REG_CMD);
> +			}
> +			break;
> +
> +		case NAND_OP_DATA_IN_INSTR:
> +			meson_nfc_read_buf(mtd, instr->ctx.data.buf.in,
> +					   instr->ctx.data.len);
> +			break;
> +
> +		case NAND_OP_DATA_OUT_INSTR:
> +			meson_nfc_write_buf(mtd, instr->ctx.data.buf.out,
> +					    instr->ctx.data.len);
> +			break;
> +
> +		case NAND_OP_WAITRDY_INSTR:
> +			meson_nfc_queue_rb(nfc, instr->ctx.waitrdy.timeout_ms);
> +			break;
> +		}
> +	}
> +	return ret;
> +}