From: "Cédric Le Goater" <clg@kaod.org>
To: Pratyush Yadav <p.yadav@ti.com>,
Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Nishanth Menon <nm@ti.com>, Tero Kristo <kristo@kernel.org>,
Rob Herring <robh+dt@kernel.org>,
Tudor Ambarus <tudor.ambarus@microchip.com>,
Michael Walle <michael@walle.cc>,
Richard Weinberger <richard@nod.at>,
Vignesh Raghavendra <vigneshr@ti.com>,
Mark Brown <broonie@kernel.org>,
<linux-arm-kernel@lists.infradead.org>,
<devicetree@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
<linux-mtd@lists.infradead.org>, <linux-spi@vger.kernel.org>,
Joel Stanley <joel@jms.id.au>
Subject: Re: [RFC PATCH 3/6] mtd: spi-nor: core: run calibration when initialization is done
Date: Wed, 18 May 2022 10:51:58 +0200 [thread overview]
Message-ID: <b3bfa5a6-caac-94ed-6741-04db9c2a9ee0@kaod.org> (raw)
In-Reply-To: <20220518075651.mvdhfnfbgutecgyq@ti.com>
Hello,
On 5/18/22 09:56, Pratyush Yadav wrote:
> On 18/05/22 09:19AM, Miquel Raynal wrote:
>> Hi Pratyush,
>>
>> p.yadav@ti.com wrote on Wed, 18 May 2022 11:37:05 +0530:
>>
>>> +Cedric
>>>
>>> On 17/05/22 04:02PM, Miquel Raynal wrote:
>>>> Hi Pratyush,
>>>>
>>>> p.yadav@ti.com wrote on Fri, 12 Mar 2021 00:42:13 +0530:
>>>>
>>>>> Once the flash is initialized tell the controller it can run
>>>>> calibration procedures if needed. This can be useful when calibration is
>>>>> needed to run at higher clock speeds.
>>>>>
>>>>> Signed-off-by: Pratyush Yadav <p.yadav@ti.com>
>>>>> ---
>>>>> drivers/mtd/spi-nor/core.c | 12 ++++++++++--
>>>>> 1 file changed, 10 insertions(+), 2 deletions(-)
>>>>>
>>>>> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
>>>>> index 88888df009f0..e0cbcaf1be89 100644
>>>>> --- a/drivers/mtd/spi-nor/core.c
>>>>> +++ b/drivers/mtd/spi-nor/core.c
>>>>> @@ -3650,6 +3650,7 @@ static int spi_nor_probe(struct spi_mem *spimem)
>>>>> * checking what's really supported using spi_mem_supports_op().
>>>>> */
>>>>> const struct spi_nor_hwcaps hwcaps = { .mask = SNOR_HWCAPS_ALL };
>>>>> + struct spi_mem_op op;
>>>>> char *flash_name;
>>>>> int ret;
>>>>>
>>>>> @@ -3709,8 +3710,15 @@ static int spi_nor_probe(struct spi_mem *spimem)
>>>>> if (ret)
>>>>> return ret;
>>>>>
>>>>> - return mtd_device_register(&nor->mtd, data ? data->parts : NULL,
>>>>> - data ? data->nr_parts : 0);
>>>>> + ret = mtd_device_register(&nor->mtd, data ? data->parts : NULL,
>>>>> + data ? data->nr_parts : 0);
>>>>> + if (ret)
>>>>> + return ret;
>>>>> +
>>>>> + op = spi_nor_spimem_get_read_op(nor);
>>>>
>>>> Isn't this too specific? I really don't know much about spi-nors, but I
>>>> find odd to have this op being created here, why not moving this into
>>>> the _do_calibration() helper?
>>>
>>> Maybe the naming confused you but this is a function in the SPI NOR
>>> core, not in SPI MEM. SPI NOR supports both SPI MEM based controllers
>>> and "legacy" controllers, so the convention is to add the "spimem"
>>> prefix before SPI MEM specific functions. So I don't get the comment
>>> about it being too specific. It is too specific to what?
>>
>> Mmh right, it's fine then.
>>
>>>
>>> And how can spi_mem_do_calibration() know what op the flash uses to read
>>> data? SPI NOR or SPI NAND would know it, but not SPI MEM. That is why we
>>> pass in that information to spi_mem_do_calibration().
>>
>> But here the op is "spi-nor wide", I would have expected a
>> per-device op. But that is not a big deal, that is something that can
>> also be updated later if needed I guess.
>
> It is per-device. The op is generated using nor->read_opcode,
> nor->addr_width, nor->read_dummy, etc. So if you have 2 NOR flashes on
> your system with different opcodes, it would work for both.
>
>>
>> One last question, is there something that mtd_device_register() does
>> that is really needed for the calibration to work? Otherwise I would
>> rather prefer to have that calibration happening before the user gets
>> access to the device.
Which would mean calling it right after :
ret = spi_nor_create_read_dirmap(nor);
if (ret)
return ret;
ret = spi_nor_create_write_dirmap(nor);
if (ret)
return ret;
> The calibration works by reading a known pattern that is already written
> to the flash again and again and seeing what delays work and what don't.
> For that to happen, the controller driver needs to know where the
> pattern is stored.
Why don't you simply choose some random place, first 16KB for instance,
and check that the data is random enough ? If not, declare calibration
not possible and choose a default safe setting which is anyhow a
requirement for calibration. Retry at reboot as data might have changed.
> This series does that by looking at the MTD
> partitions. For that to happen, we need to create those partitions
> first, which happens after mtd_device_register().
hmm, that might work for some boards. This is not at all the case for
the BMC boards. Vendors can put any kind of flash model and/or layout
and the driver needs to be more generic.
> But I am planning to use device tree to get that information now so this
> should no longer be needed and we can do calibration before registering
> the device with MTD.
Perfect, we can move the calibration hook in spi_nor_create_read_dirmap()
then, or in devm_spi_mem_dirmap_create(), which would make more sense IMHO.
Thanks,
C.
______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/
next prev parent reply other threads:[~2022-05-18 8:52 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-11 19:12 [RFC PATCH 0/6] spi: Add OSPI PHY calibration support for spi-cadence-quadspi Pratyush Yadav
2021-03-11 19:12 ` [RFC PATCH 1/6] spi: spi-mem: Tell controller when device is ready for calibration Pratyush Yadav
2021-03-23 23:07 ` Michael Walle
2021-03-24 8:08 ` Pratyush Yadav
2021-04-29 16:23 ` Michael Walle
2021-04-29 18:41 ` Pratyush Yadav
2021-04-29 22:46 ` Michael Walle
2021-03-11 19:12 ` [RFC PATCH 2/6] mtd: spi-nor: core: consolidate read op creation Pratyush Yadav
2021-03-23 23:17 ` Michael Walle
2021-03-24 8:04 ` Pratyush Yadav
2021-04-08 12:48 ` Michael Walle
2021-03-11 19:12 ` [RFC PATCH 3/6] mtd: spi-nor: core: run calibration when initialization is done Pratyush Yadav
2022-05-17 14:02 ` Miquel Raynal
2022-05-18 6:07 ` Pratyush Yadav
2022-05-18 7:19 ` Miquel Raynal
2022-05-18 7:56 ` Pratyush Yadav
2022-05-18 8:51 ` Cédric Le Goater [this message]
2022-06-27 9:14 ` Pratyush Yadav
2022-06-27 9:43 ` Cédric Le Goater
2022-06-27 10:35 ` Pratyush Yadav
2021-03-11 19:12 ` [RFC PATCH 4/6] spi: cadence-qspi: Use PHY for DAC reads if possible Pratyush Yadav
2021-03-12 9:13 ` Tudor.Ambarus
2021-03-12 10:17 ` Pratyush Yadav
2021-04-29 16:28 ` Michael Walle
2021-04-29 18:19 ` Pratyush Yadav
2021-04-29 22:20 ` Michael Walle
2021-05-10 11:39 ` Pratyush Yadav
2021-03-11 19:12 ` [RFC PATCH 5/6] spi: cadence-qspi: Tune PHY to allow running at higher frequencies Pratyush Yadav
2021-04-29 22:48 ` Michael Walle
2021-04-30 5:42 ` Pratyush Yadav
2021-03-11 19:12 ` [RFC PATCH 6/6] arm64: dts: ti: k3-j721e-som-p0: Enable PHY calibration Pratyush Yadav
2021-03-12 9:09 ` [RFC PATCH 0/6] spi: Add OSPI PHY calibration support for spi-cadence-quadspi Tudor.Ambarus
2021-03-12 10:10 ` Pratyush Yadav
2021-03-12 10:20 ` Michael Walle
2021-03-12 11:07 ` Pratyush Yadav
2021-03-12 13:26 ` Michael Walle
2021-03-12 11:23 ` Tudor.Ambarus
2021-03-12 18:14 ` Pratyush Yadav
2021-03-12 13:32 ` Michael Walle
2021-03-12 14:59 ` Tudor.Ambarus
2021-03-12 17:00 ` Pratyush Yadav
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=b3bfa5a6-caac-94ed-6741-04db9c2a9ee0@kaod.org \
--to=clg@kaod.org \
--cc=broonie@kernel.org \
--cc=devicetree@vger.kernel.org \
--cc=joel@jms.id.au \
--cc=kristo@kernel.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mtd@lists.infradead.org \
--cc=linux-spi@vger.kernel.org \
--cc=michael@walle.cc \
--cc=miquel.raynal@bootlin.com \
--cc=nm@ti.com \
--cc=p.yadav@ti.com \
--cc=richard@nod.at \
--cc=robh+dt@kernel.org \
--cc=tudor.ambarus@microchip.com \
--cc=vigneshr@ti.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).