From: <Tudor.Ambarus@microchip.com>
To: <michael@walle.cc>, <tkuw584924@gmail.com>
Cc: <linux-mtd@lists.infradead.org>, <miquel.raynal@bootlin.com>,
<richard@nod.at>, <vigneshr@ti.com>, <p.yadav@ti.com>,
<Bacem.Daassi@infineon.com>, <Takahiro.Kuwano@infineon.com>
Subject: Re: [PATCH v15 6/8] mtd: spi-nor: Retain nor->addr_width at 4BAIT parse
Date: Thu, 21 Jul 2022 16:06:44 +0000 [thread overview]
Message-ID: <c42d5930-73cd-6dbe-f650-db72f35188a5@microchip.com> (raw)
In-Reply-To: <4d8146ceecf1f8a89c6a43fa1ac8d81e@walle.cc>
On 5/23/22 10:49, Michael Walle wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>
> Am 2022-05-14 05:51, schrieb Takahiro Kuwano:
>> On 5/13/2022 6:40 PM, Michael Walle wrote:
>>> [btw the subject still has the old name of the addr_width]
>>>
>> Yes, it must be fixed in next rev.
>>
>>> Am 2022-05-13 03:26, schrieb Takahiro Kuwano:
>>>> On 5/13/2022 7:14 AM, Michael Walle wrote:
>>>>> Am 2022-05-10 00:10, schrieb tkuw584924@gmail.com:
>>>>>> From: Takahiro Kuwano <Takahiro.Kuwano@infineon.com>
>>>>>>
>>>>>> In 4BAIT parse, keep nor->params->addr_width because it may be used
>>>>>> as
>>>>>> current address mode in SMPT parse later on.
>>>>>
>>>>> Mh I'm not sure this is needed at all.
>>>>>
>>>>> SFDP spec says
>>>>> Variable address length (the current setting of the address
>>>>> length mode defines the address length)
>>>>>
>>>>> and
>>>>> When the length is defined as variable, the software or hardware
>>>>> controlling the memory is aware of the address length mode last
>>>>> set in the memory device and this same length of address.
>>>>>
>>>>> We don't set any address mode until all the SFDP parsing is
>>>>> over. Therefore we should always be in 3 byte mode, no?
>>>>>
>>>> Actually there are some devices that have variable address length but
>>>> 4 byte mode by default (I will work on those devices after this
>>>> series
>>>> is settled). To support such case, I prefer to use
>>>> params->addr_nbytes
>>>> as current address mode so that I can fix it in post_bfpt_fixup()
>>>> hook.
>>>
>>> Are there public datasheets available? So these devices have a 3 byte
>> I will send datasheets to you in another email. At this point, only
>> summary datasheet is available in website.
>>
>>> and a 4 byte mode, but after reset, they are in the 4 byte mode? Looks
>> Yes.
>>
>>> like it should be fixed in a different way. I'm not sure the "current
>>> mode" handling is correct.
>>>
>> Yes, we may want to introduce a new flag like SPI_NOR_4BAM_DEFAULT and
>> check
>> the flag in BFPT parse. Once I send another series, please review.
>>
>>> We need to differentiate between the mode the flash currently is using
>>> (nor->addr_nbytes) and the mode parsed by SFDP (params->addr_nbytes).
>>>
>> The flash's address mode affects the address length of Non-4B opcodes,
>> including read/write any register ops used in SMPT parse and Infineon
>> (spansion) specific hooks.
>>
>> The 4B opcodes always take address length of 4 regardless of flash's
>> address mode. In these Infineon chips, 4B opcodes for read/program/
>> erase are available and 4BAIT advertises them. We don't have to enter
>> 4 byte address mode for read/program/erase.
>
> btw. this is a pity. you are using the stateless 4b opcodes but
> then you don't provide stateless opcodes for the read any register
> op :/
>
>> So, I think we need to differentiate between address length for
>> read/program/erase and flash's default address mode.
>
> Or we keep them in sync. E.g. switch to 4bytes mode if we are
> using the 4 byte. Granted, that sounds like a hack :)
>
>> Obviously we are using nor->addr_nbytes as address length for read/
>> program/erase and should keep this usage.
>
> Yes, I wasn't aware that we actually two different runtime
> parameters:
> - the read/program/erase address width, also used with the
> 4b opcodes
> - internal mode 3b/4b. Up until now, this wasn't an issue
> because either the mode was switched or the 4b opcodes
> were used. So this was mutually exclusive. Now we have
> flashes which uses 4b opcodes _and_ we need the state
> of the internal mode.
>
> I can't think of a good solution for now. Need to think
> more about this, but I'm pretty busy at the moment.
> What I think is clear is that we need two different modes
> here in the spi_nor struct. nor->addr_nbytes for the
> read/program/erase opcodes and nor->address_mode or similar
> which tracks the SPI flash's internal address mode.
Hi, Takahiro,
Can we determine the flash's internal address mode by querying
the flash at run-time? Is this possible on Semper flashes?
To extend the idea, when the flash supports BFPT and defines
BFPT_DWORD1_ADDRESS_BYTES_3_ONLY or BFPT_DWORD1_ADDRESS_BYTES_4_ONLY
the things are clear, addr_nbytes is fixed.
If the flash does not define BFPT or uses
BFPT_DWORD1_ADDRESS_BYTES_3_OR_4, then we could determine the addr
mode by querying the flash.
>
>> For flash's default address mode, my preference is to use
>> params->addr_nbytes, but I should rename it to something like
>> params->def_addr_nbytes and rework spi_nor_set_addr_nbytes().
>
> IMHO params should only be used to store the parsed (or
> hardcoded) parameters.
yep, I share Michael's opinion.
Cheers,
ta
>
> -michael
>
>> static int spi_nor_set_addr_nbytes(struct spi_nor *nor)
>> {
>> if (nor->flags & SNOR_F_HAS_4BAIT) {
>> nor->addr_nbytes = 4;
>> } else if (nor->params->def_addr_nbytes) {
>> nor->addr_nbytes = nor->params->def_addr_nbytes;
>>
>>> At some point, the mode is switched and nor->addr_nbytes becomes
>>> params->addr_nbytes. It seems in your case nor->addr_nbytes should
>>> be 4 right from the beginning. Which also means nor->addr_nbytes
>>> should be 3 for the other cases (and probably not 0).
>>>
>> With param->def_addr_nbytes, I think we can keep nor->addr_nbytes = 0
>> during SFDP parse.
>>
>> Thanks,
>> Takahiro
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next prev parent reply other threads:[~2022-07-21 16:11 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-09 22:10 [PATCH v15 0/8] mtd: spi-nor: Add support for Infineon s25hl-t/s25hs-t tkuw584924
2022-05-09 22:10 ` [PATCH v15 1/8] mtd: spi-nor: s/addr_width/addr_nbytes tkuw584924
2022-05-12 21:01 ` Michael Walle
2022-05-31 11:13 ` Pratyush Yadav
2022-05-09 22:10 ` [PATCH v15 2/8] mtd: spi-nor: core: Shrink the storage size of the flash_info's addr_nbytes tkuw584924
2022-05-12 21:22 ` Michael Walle
2022-05-31 11:14 ` Pratyush Yadav
2022-05-09 22:10 ` [PATCH v15 3/8] mtd: spi-nor: sfdp: Clarify that nor->read_{opcode, dummy} are uninitialized tkuw584924
2022-05-12 21:33 ` Michael Walle
2022-05-12 21:38 ` Michael Walle
2022-05-31 11:18 ` Pratyush Yadav
2022-05-09 22:10 ` [PATCH v15 4/8] mtd: spi-nor: Do not change nor->addr_nbytes at SFDP parsing time tkuw584924
2022-05-12 21:45 ` Michael Walle
2022-05-31 11:30 ` Pratyush Yadav
2022-07-21 14:32 ` Tudor.Ambarus
2022-07-21 15:02 ` Tudor.Ambarus
2022-05-09 22:10 ` [PATCH v15 5/8] mtd: spi-nor: core: Couple the number of address bytes with the address mode tkuw584924
2022-05-12 22:07 ` Michael Walle
2022-05-09 22:10 ` [PATCH v15 6/8] mtd: spi-nor: Retain nor->addr_width at 4BAIT parse tkuw584924
2022-05-12 22:14 ` Michael Walle
2022-05-13 1:26 ` Takahiro Kuwano
2022-05-13 9:40 ` Michael Walle
2022-05-14 3:51 ` Takahiro Kuwano
2022-05-18 6:04 ` Takahiro Kuwano
2022-05-18 8:35 ` Michael Walle
2022-05-18 9:12 ` Takahiro Kuwano
2022-05-23 7:49 ` Michael Walle
2022-05-23 9:56 ` Takahiro Kuwano
2022-06-03 9:33 ` Takahiro Kuwano
2022-07-21 16:06 ` Tudor.Ambarus [this message]
2022-07-22 4:00 ` Takahiro Kuwano
2022-07-22 4:20 ` Tudor.Ambarus
2022-07-22 4:31 ` Vanessa Page
2022-07-22 4:46 ` Takahiro Kuwano
2022-07-22 5:06 ` Tudor.Ambarus
2022-07-22 5:11 ` Takahiro Kuwano
2022-07-22 6:08 ` Tudor.Ambarus
2022-07-22 7:38 ` Tudor.Ambarus
2022-07-22 7:45 ` Tudor.Ambarus
2022-06-08 11:39 ` Tudor.Ambarus
2022-05-09 22:10 ` [PATCH v15 7/8] mtd: spi-nor: spansion: Add local function to discover page size tkuw584924
2022-05-09 22:10 ` [PATCH v15 8/8] mtd: spi-nor: spansion: Add s25hl-t/s25hs-t IDs and fixups tkuw584924
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