From: Harald Mommer <harald.mommer@opensynergy.com>
To: Haixu Cui <quic_haixcui@quicinc.com>,
virtio-dev@lists.oasis-open.org, Mark Brown <broonie@kernel.org>,
Viresh Kumar <viresh.kumar@linaro.org>,
linux-spi@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: quic_ztu@quicinc.com, Matti Moell <Matti.Moell@opensynergy.com>,
Mikhail Golubev <Mikhail.Golubev@opensynergy.com>
Subject: Re: [virtio-dev] Re: [RFC PATCH v2 3/3] SPI: Add virtio SPI driver (V10 draft specification).
Date: Thu, 1 Feb 2024 18:26:32 +0100 [thread overview]
Message-ID: <31c94125-06e3-4459-9688-d371fcc87b2a@opensynergy.com> (raw)
In-Reply-To: <6171c1c3-55ba-4f74-ae60-764820cf1caf@quicinc.com>
Hello Haixu,
Thanks. This was a hard one. I knew that I did the delay settingsmost
probably somewhat wrong but I had no idea that I did it so wrong.
Reworked, made a new function for this, currently testing. Added the
link to the place where your E-Mail is stored
https://lore.kernel.org/all/6171c1c3-55ba-4f74-ae60-764820cf1caf@quicinc.com/
as a comment to the source code and hope this will survive the reviews.
Another option would be to add the diagram + the explanations below as
quoted here as comment to the code. Whether 30+ lines of comments would
survive the reviews I don't know.
Just to say nothing in the code making live hard for people trying to
understand the code is something I would like to avoid.
Regards
Harald
On 30.01.24 04:21, Haixu Cui wrote:
> . . . . . . . . . .
> Delay + A + + B + + C + D + E + F + A +
> . . . . . . . . . .
> ___. . . . . . .___.___. .
> CS# |___.______.____.____.___.___| . |___._____________
> . . . . . . . . . .
> . . . . . . . . . .
> SCLK__.___.___NNN_____NNN__.___.___.___.___.___.___NNN_______
>
>
> NOTE: 1st transfer has two words, the delay betweent these two words
> are 'B' in the diagram.
>
> A => struct spi_device -> cs_setup
> B => max{struct spi_transfer -> word_delay,
> struct spi_device -> word_delay}
> Note: spi_device and spi_transfer both have word_delay, Linux
> choose the bigger one, refer to _spi_xfer_word_delay_update
> function
> C => struct spi_transfer -> delay
> D => struct spi_device -> cs_hold
> E => struct spi_device -> cs_inactive
> F => struct spi_transfer -> cs_change_delay
>
> So the corresponding relationship:
> A <===> cs_setup_ns (after CS asserted)
> B <===> word_delay_ns (no matter with CS)
> C+D <===> cs_delay_hold_ns (before CS deasserted)
> E+F <===> cs_change_delay_inactive_ns (after CS deasserted, these two
> values also recommend in Linux driver to be added up)
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prev parent reply other threads:[~2024-02-01 17:26 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-04 13:01 [virtio-dev] [RFC PATCH v2 0/3] Virtio SPI Linux driver compliant to draft spec V10 Harald Mommer
2024-01-04 13:01 ` [virtio-dev] [RFC PATCH v2 1/3] virtio: Add ID for virtio SPI Harald Mommer
2024-01-29 6:30 ` [virtio-dev] " Viresh Kumar
2024-01-04 13:01 ` [virtio-dev] [RFC PATCH v2 2/3] virtio-spi: Add virtio-spi.h (V10 draft specification) Harald Mommer
2024-01-29 6:39 ` [virtio-dev] " Viresh Kumar
2024-01-04 13:01 ` [virtio-dev] [RFC PATCH v2 3/3] SPI: Add virtio SPI driver " Harald Mommer
2024-01-29 7:06 ` [virtio-dev] " Viresh Kumar
2024-01-30 14:24 ` Harald Mommer
2024-01-30 3:21 ` Haixu Cui
2024-02-01 17:26 ` Harald Mommer [this message]
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