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

From: Gregor Herburger <gregor.herburger@ew.tq-group.com>
To: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>,
	Thomas Kopp <thomas.kopp@microchip.com>,
	Vincent Mailhol <mailhol.vincent@wanadoo.fr>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Rob Herring <robh@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Conor Dooley <conor+dt@kernel.org>,
	linux-can@vger.kernel.org, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org, devicetree@vger.kernel.org,
	linux@ew.tq-group.com, alexander.stein@ew.tq-group.com
Subject: Re: Re: [PATCH 1/4] can: mcp251xfd: stop timestamp before sending chip to sleep
Date: Thu, 25 Apr 2024 11:44:36 +0200	[thread overview]
Message-ID: <ZiomBNoSsXlYfKN2@herburgerg-w2> (raw)
In-Reply-To: <20240425-tall-quiet-wren-f00e44-mkl@pengutronix.de>

On Thu, Apr 25, 2024 at 08:29:13AM +0200, Marc Kleine-Budde wrote:
> 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.

Ah I see. Currently the GPIO rigister is cached and only written to the
chip if the netdevice is set up. I think to have a more generic gpio controller
the chip should wake up when the GPIO is requested. Also the chip should
not go to sleep while GPIO is requested and netdevice is set down.

> 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.

I will have a look at them.
> 
> regards,
> Marc
> 
> -- 
> Pengutronix e.K.                 | Marc Kleine-Budde          |
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Best regards
Gregor
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