linux-kernel - Re: [PATCH v10 1/6] mtd: spi-nor: add Octal DTR support for Macronix flash

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Message-ID: <890c1926-2778-41e3-bca6-d08a5a493708@linaro.org>
Date: Fri, 4 Oct 2024 10:58:55 +0100
From: Tudor Ambarus <tudor.ambarus@...aro.org>
To: Alvin Zhou <alvinzhou.tw@...il.com>
Cc: linux-mtd@...ts.infradead.org, linux-spi@...r.kernel.org,
 linux-kernel@...r.kernel.org, pratyush@...nel.org, mwalle@...nel.org,
 miquel.raynal@...tlin.com, richard@....at, vigneshr@...com,
 broonie@...nel.org, chengminglin@...c.com.tw, leoyu@...c.com.tw,
 AlvinZhou <alvinzhou@...c.com.tw>, JaimeLiao <jaimeliao@...c.com.tw>
Subject: Re: [PATCH v10 1/6] mtd: spi-nor: add Octal DTR support for Macronix
 flash



On 10/4/24 10:05 AM, Alvin Zhou wrote:
>>> +     /* Read flash ID to make sure the switch was successful. */
>>> +     ret = spi_nor_read_id(nor, 4, 4, buf, SNOR_PROTO_8_8_8_DTR);
>> can we use nor->addr_nbytes for the second argument? Please test and
>> confirm. No need to resend for this, just confirm and I can amend when
>> applying.
> The following is the process of spi_nor_scan()
> int spi_nor_scan(...)
> {
> ......
> ret = spi_nor_init_params(nor);
> ......
> ret = spi_nor_setup(nor, hwcaps);
> ......
> }
> First, within the spi_nor_parse_sfdp() function inside
> spi_nor_init_params(): nor->params->addr_nbytes is set based on the
> SFDP, while nor->addr_nbytes is not available. Therefore, the second
> argument cannot use nor->addr_nbytes but can use
> nor->params->addr_nbytes. Additionally, For Macronix Octal NOR Flash


nor->addr_nbytes is set in spi_nor_setup().
spi_nor_set_octal_dtr() is called after spi_nor_setup(), thus you can
use nor->addr_nbytes.

> in Octal DDR mode, both the address and dummy cycles are fixed at 4
> in READID, so setting the second and third argument to 4 is also valid.

but we don't want magic numbers or states that are not tracked, so use
the parameters set

> Moreover, nor->addr_nbytes is set within the spi_nor_setup() function.

yep, use it then.