All of lore.kernel.org
 help / color / mirror / Atom feed
From: Pratyush Yadav <pratyush@kernel.org>
To: "William A. Kennington III" <william@wkennington.com>
Cc: Tudor Ambarus <tudor.ambarus@linaro.org>,
	 Pratyush Yadav <pratyush@kernel.org>,
	 Michael Walle <mwalle@kernel.org>,
	linux-mtd@lists.infradead.org,  linux-kernel@vger.kernel.org
Subject: Re: [PATCH RFC] mtd: spi-nor: Sleep between ready checks
Date: Tue, 27 May 2025 18:48:17 +0200	[thread overview]
Message-ID: <mafs0a56yrodq.fsf@kernel.org> (raw)
In-Reply-To: <20250523001412.878560-1-william@wkennington.com>

Hi William,

On Thu, May 22 2025, William A. Kennington III wrote:

> We have SPI NOR devices that respond very slowly (200ms+) to some
> commands. This causes our CPU to stall while repeatedly polling the NOR
> with no cooldown in between attempts. In order to reduce overhead, this
> patch introduces an exponential backoff in SPI readiness polling, that
> self tunes the polling interval to match the speed of most transactions.
>
> Signed-off-by: William A. Kennington III <william@wkennington.com>

I didn't read the code too deeply, but it seems full of magic values and
I am honestly not a big fan of how it reads. At the very least the logic
should be less black-magic. But since I didn't spend too much time
understanding the code, I don't have specific feedback for you.

BTW, you say it causes CPU stalls. The loop has a cond_resched() after
every iteration which I think gives the scheduler a chance to run other
tasks. Does that not work for some reason?

[...]

-- 
Regards,
Pratyush Yadav

______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/

WARNING: multiple messages have this Message-ID (diff)
From: Pratyush Yadav <pratyush@kernel.org>
To: "William A. Kennington III" <william@wkennington.com>
Cc: Tudor Ambarus <tudor.ambarus@linaro.org>,
	 Pratyush Yadav <pratyush@kernel.org>,
	 Michael Walle <mwalle@kernel.org>,
	linux-mtd@lists.infradead.org,  linux-kernel@vger.kernel.org
Subject: Re: [PATCH RFC] mtd: spi-nor: Sleep between ready checks
Date: Tue, 27 May 2025 18:48:17 +0200	[thread overview]
Message-ID: <mafs0a56yrodq.fsf@kernel.org> (raw)
In-Reply-To: <20250523001412.878560-1-william@wkennington.com>

Hi William,

On Thu, May 22 2025, William A. Kennington III wrote:

> We have SPI NOR devices that respond very slowly (200ms+) to some
> commands. This causes our CPU to stall while repeatedly polling the NOR
> with no cooldown in between attempts. In order to reduce overhead, this
> patch introduces an exponential backoff in SPI readiness polling, that
> self tunes the polling interval to match the speed of most transactions.
>
> Signed-off-by: William A. Kennington III <william@wkennington.com>

I didn't read the code too deeply, but it seems full of magic values and
I am honestly not a big fan of how it reads. At the very least the logic
should be less black-magic. But since I didn't spend too much time
understanding the code, I don't have specific feedback for you.

BTW, you say it causes CPU stalls. The loop has a cond_resched() after
every iteration which I think gives the scheduler a chance to run other
tasks. Does that not work for some reason?

[...]

-- 
Regards,
Pratyush Yadav

  reply	other threads:[~2025-05-27 16:48 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-05-23  0:14 [PATCH RFC] mtd: spi-nor: Sleep between ready checks William A. Kennington III
2025-05-23  0:14 ` William A. Kennington III
2025-05-27 16:48 ` Pratyush Yadav [this message]
2025-05-27 16:48   ` 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=mafs0a56yrodq.fsf@kernel.org \
    --to=pratyush@kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mtd@lists.infradead.org \
    --cc=mwalle@kernel.org \
    --cc=tudor.ambarus@linaro.org \
    --cc=william@wkennington.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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.