Messages in this thread | | | From | Andy Shevchenko <> | Date | Wed, 22 Jun 2022 12:52:02 +0200 | Subject | Re: [PATCH v2 7/9] driver core: Set fw_devlink.strict=1 by default |
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On Wed, Jun 22, 2022 at 10:44 AM Linus Walleij <linus.walleij@linaro.org> wrote: > On Wed, Jun 22, 2022 at 9:48 AM Sascha Hauer <sha@pengutronix.de> wrote:
...
> > This patch has the effect that console UART devices which have "dmas" > > properties specified in the device tree get deferred for 10 to 20 > > seconds. This happens on i.MX and likely on other SoCs as well. On i.MX > > the dma channel is only requested at UART startup time and not at probe > > time. dma is not used for the console. Nevertheless with this driver probe > > defers until the dma engine driver is available. > > > > It shouldn't go in as-is. > > This affects all machines with the PL011 UART and DMAs specified as > well. > > It would be best if the console subsystem could be treated special and > not require DMA devlink to be satisfied before probing.
In 8250 we force disable DMA and PM on kernel consoles, because it's so-o PITA and has a lot of corner cases we may never chase down.
089b6d365491 serial: 8250_port: Disable DMA operations for kernel console bedb404e91bb serial: 8250_port: Don't use power management for kernel console
> It seems devlink is not quite aware of the concept of resources that are > necessary to probe vs resources that are nice to have and might be > added after probe. We need a strong devlink for the first category > and maybe a weak devlink for the latter category. > > I don't know if this is a generic hardware property for all operating > systems so it could be a DT property such as dma-weak-dependency? > Or maybe compromize and add a linux,dma-weak-dependency; > property?
-- With Best Regards, Andy Shevchenko
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