Re: [PATCH v3 1/6] dmaengine: dw-edma: fix dw_edma_probe() can't be call globally

From: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
To: Serge Semin <fancer.lancer@gmail.com>
Cc: Frank Li <Frank.Li@nxp.com>,
	Serge Semin <Sergey.Semin@baikalelectronics.ru>,
	gustavo.pimentel@synopsys.com, hongxing.zhu@nxp.com,
	l.stach@pengutronix.de, linux-imx@nxp.com,
	linux-pci@vger.kernel.org, dmaengine@vger.kernel.org,
	lznuaa@gmail.com, vkoul@kernel.org, lorenzo.pieralisi@arm.com,
	robh@kernel.org, kw@linux.com, bhelgaas@google.com,
	shawnguo@kernel.org
Subject: Re: [PATCH v3 1/6] dmaengine: dw-edma: fix dw_edma_probe() can't be call globally
Date: Thu, 10 Mar 2022 11:52:42 +0530	[thread overview]
Message-ID: <20220310062242.GB4869@thinkpad> (raw)
In-Reply-To: <20220309190123.dnivojpqhl52o5vc@mobilestation>

On Wed, Mar 09, 2022 at 10:01:23PM +0300, Serge Semin wrote:

[...]

> > I'm afraid that this will not work for all cases (unless I miss something). As
> > Zhi Li pointed out, there are places where only chip pointer will be passed and
> > we'd need to extract the private data (dw_edma) from it.
> > 
> > Tbh I also considered your idea but because of the above mentioned issue and
> > also referring to other implementations like gpiochip, I settled with Frank's
> > idea of copying the fields.
> 
> What places are these? I see the only obstacle is the dw_edma_remove()
> method. But it's easily fixable.

Yeah, right. I overlooked that part.

> Except that, everything else is more
> or less straightforward (just a few methods need to have prototypes
> converted to accepting dw_edma instead dw_edma_chip).
> 
> In order to make the code design more coherent, we need to split up
> private data and device/platform info. As I see it dw_edma_chip is
> nothing but a chip info data. The eDMA driver is supposed to mainly
> use and pass it's private data, not the platform info. It will greatly
> improve the code readability and maintainability. Such approach will
> also prevent a temptation of adding new private data fields into the
> dw_edma_chip structure since reaching the pointer to dw_edma will be
> much easier that getting the dw_edma_chip data. In this case
> dw_edma_chip will be something like i2c_board_info in i2c.
> 
> Ideally dw_edma_chip could be a temporarily defined device info, which
> memory after the dw_edma_probe() method invocation could be freed. But
> in order to implement that we'd need a bit more modifications
> introduced.
> 

While at it, we should also consider adding an ops structure for passing the
callbacks from controller drivers. Currently the eDMA driver has the callbacks
defined in v0-core.c but it is used directly instead of as a callback.

This should anyway needs to be fixed when another version of the IP get's added.

Thanks,
Mani