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Message-ID: <f55ab390-a784-d598-8d0e-b78040fdbb73@broadcom.com>
Date: Mon, 9 Jan 2023 12:18:09 -0800
From: William Zhang <william.zhang@...adcom.com>
To: Mark Brown <broonie@...nel.org>
Cc: Rob Herring <robh+dt@...nel.org>,
Linux SPI List <linux-spi@...r.kernel.org>,
Broadcom Kernel List <bcm-kernel-feedback-list@...adcom.com>,
anand.gore@...adcom.com, tomer.yacoby@...adcom.com,
dan.beygelman@...adcom.com, joel.peshkin@...adcom.com,
f.fainelli@...il.com, jonas.gorski@...il.com,
kursad.oney@...adcom.com, dregan@...l.com,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/16] dt-bindings: spi: Add spi peripheral specific
property
Hi Mark,
On 01/09/2023 11:19 AM, Mark Brown wrote:
> On Mon, Jan 09, 2023 at 12:06:13AM -0800, William Zhang wrote:
>>> On Fri, Jan 6, 2023 at 9:27 PM William Zhang <william.zhang@...adcom.com> wrote:
>
>>> Keeping the clock on or not would affect all devices unless you have a
>>> per device clock you can gate, so making this a per device flag
>>> doesn't make sense.
>
>> This applies only to each chip select. There is only one device under each
>> chip select. So won't impact any other devices under other cs.
>
> I don't understand how this would work - usually a SPI controller has a
> single set of clock, MOSI and MISO lines with the only per device thing
> being the chip select. If the clock line is used by all devices then it
> must be kept on for all of them if it's to be kept on for one of them.
>
This setting is set per spi message for particular chip select of the
device when starting the message through bcm63xx_hsspi_set_clk function
and restore to default(clock gating) when message is done through
bcm63xx_hsspi_restore_clk_gate.
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