linux-kernel - Re: [PATCH 1/4] can: mcp251xfd: stop timestamp before sending chip to sleep

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Message-ID: <20240425-tall-quiet-wren-f00e44-mkl@pengutronix.de>
Date: Thu, 25 Apr 2024 08:29:13 +0200
From: Marc Kleine-Budde <mkl@...gutronix.de>
To: Gregor Herburger <gregor.herburger@...tq-group.com>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>, 
	Thomas Kopp <thomas.kopp@...rochip.com>, Vincent Mailhol <mailhol.vincent@...adoo.fr>, 
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>, linux-can@...r.kernel.org, 
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org, devicetree@...r.kernel.org, 
	linux@...tq-group.com, alexander.stein@...tq-group.com
Subject: Re: [PATCH 1/4] can: mcp251xfd: stop timestamp before sending chip
 to sleep

On 25.04.2024 07:17:11, Gregor Herburger wrote:
> On Wed, Apr 24, 2024 at 01:54:54PM +0200, Marc Kleine-Budde wrote:
> > On 17.04.2024 15:43:54, Gregor Herburger wrote:
> > > MCP2518FD exits Low-Power Mode (LPM) when CS is asserted. When chip
> > > is send to sleep and the timestamp workqueue is not stopped chip is
> > > waked by SPI transfer of mcp251xfd_timestamp_read.
> > 
> > How does the Low-Power Mode affect the GPIO lines? Is there a difference
> > if the device is only in sleep mode?
> 
> The MCP251XFD_REG_IOCON is cleared when leaving Low-Power Mode. This is
> why I implemented regcache.

But that means you have to power the chip if a GPIO is requested. You
have to power up the chip in the request() callback and power it down in
the free() callback.

I've 2 patches laying around, one that moves the timestamp
init/start/stop into the chip_start/stop. And another one that moves the
soft reset and basic configuration of the chip into the runtime pm
functions. I have to make both patches compatible and send them to the
list. Feel free to pick them up and integrate them into your series.

regards,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde          |
Embedded Linux                   | https://www.pengutronix.de |
Vertretung Nürnberg              | Phone: +49-5121-206917-129 |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-9   |

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