Linux-ARM-MSM Archive on
 help / color / Atom feed
From: Marc Gonzalez <>
To: Kishon Vijay Abraham I <>,
	Vivek Gautam <>,
	Bjorn Andersson <>,
	Douglas Anderson <>
Cc: MSM <>, LKML <>
Subject: Re: [PATCH v1] phy: qcom-qmp: Raise qcom_qmp_phy_enable() polling delay
Date: Mon, 24 Jun 2019 13:55:57 +0200
Message-ID: <> (raw)
In-Reply-To: <>

On 20/06/2019 08:25, Kishon Vijay Abraham I wrote:

> On 14/06/19 6:08 PM, Marc Gonzalez wrote:
>> The issue is usleep_range() being misused ^_^
>> Although usleep_range() takes unsigned longs as parameters, it is
>> not appropriate over the entire 0-2^64 range.
>> a) It should not be used with tiny values, because the cost of programming
>> the timer interrupt, and processing the resulting IRQ would dominate.
>> b) It should not be used with large values (above 2000000/HZ) because
>> msleep() is more efficient, and is acceptable for these ranges.
> Documentation/timers/timers-howto.txt has all the information on the various
> kernel delay/sleep mechanisms. For < ~10us, it recommends to use udelay
> (readx_poll_timeout_atomic). Depending on the actual timeout to be used, the
> delay mechanism in timers-howto.txt should be used.

Hello Kishon,

I believe the proposed patch does the right thing:

a) polling for the ready bit is not done in atomic context,
therefore we don't need to busy-loop

b) since we're ultimately calling usleep_range(), we should
pass an appropriate parameter, such as max_us = 10
(instead of max_us = 1, which is outside usleep_range spec)

Maybe it would help if someone reviewed this patch.


  reply index

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-13 11:32 Marc Gonzalez
2019-06-14  9:50 ` Vivek Gautam
2019-06-14 12:38   ` Marc Gonzalez
2019-06-20  6:25     ` Kishon Vijay Abraham I
2019-06-24 11:55       ` Marc Gonzalez [this message]
2019-06-24 15:52 ` Doug Anderson

Reply instructions:

You may reply publically 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:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \ \ \ \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-ARM-MSM Archive on

Archives are clonable:
	git clone --mirror linux-arm-msm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-arm-msm linux-arm-msm/ \
	public-inbox-index linux-arm-msm

Newsgroup available over NNTP:

AGPL code for this site: git clone public-inbox