linux-kernel - Re: [PATCH v4] dmaengine: qcom: Add ADM driver

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Date:   Mon, 9 Nov 2020 19:04:16 +0000
From:   Jonathan McDowell <noodles@...th.li>
To:     Vinod Koul <vkoul@...nel.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Thomas Pedersen <twp@...eaurora.org>,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        dmaengine@...r.kernel.org
Subject: Re: [PATCH v4] dmaengine: qcom: Add ADM driver

On Mon, Nov 09, 2020 at 05:11:21PM +0530, Vinod Koul wrote:
> HI Jonathan,
> 
> On 23-09-20, 20:40, Jonathan McDowell wrote:
> > Add the DMA engine driver for the QCOM Application Data Mover (ADM) DMA
> > controller found in the MSM8x60 and IPQ/APQ8064 platforms.
> 
> Mostly it looks good, some nitpicks
> 
> > The ADM supports both memory to memory transactions and memory
> > to/from peripheral device transactions.  The controller also provides
> > flow control capabilities for transactions to/from peripheral devices.
> > 
> > The initial release of this driver supports slave transfers to/from
> > peripherals and also incorporates CRCI (client rate control interface)
> > flow control.
> 
> Can you also convert the binding from txt to yaml?

Seems like that can be a separate patch, but sure, I'll give it a whirl.

> > diff --git a/drivers/dma/qcom/Kconfig b/drivers/dma/qcom/Kconfig
> > index 3bcb689162c6..0389d60d2604 100644
> > --- a/drivers/dma/qcom/Kconfig
> > +++ b/drivers/dma/qcom/Kconfig
> > @@ -1,4 +1,15 @@
> >  # SPDX-License-Identifier: GPL-2.0-only
> > +config QCOM_ADM
> > +	tristate "Qualcomm ADM support"
> > +	depends on (ARCH_QCOM || COMPILE_TEST) && !PHYS_ADDR_T_64BIT
> 
> why !PHYS_ADDR_T_64BIT ..?

The hardware only supports a 32 bit physical address, so specifying
!PHYS_ADDR_T_64BIT gives maximum COMPILE_TEST coverage without having to
spend effort on kludging things in the code that will never actually be
needed on real hardware.

> > +	select DMA_ENGINE
> > +	select DMA_VIRTUAL_CHANNELS
> > +	help
> > +	  Enable support for the Qualcomm Application Data Mover (ADM) DMA
> > +	  controller, as present on MSM8x60, APQ8064, and IPQ8064 devices.
> > +	  This controller provides DMA capabilities for both general purpose
> > +	  and on-chip peripheral devices.
> 
> > +static const struct of_device_id adm_of_match[] = {
> > +	{ .compatible = "qcom,adm", },
> 
> I know we have merged the binding, but should we not have a soc specific
> compatible?

Which soc? Looking at the other QCOM DMA drivers they mostly have
versioned compatibles and I can't find any indication there are multiple
variants of this block out there.

J.

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