linux-kernel - Re: [RFC PATCH 4/5] spi: qpic: Add support for qpic spi nand driver

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Date:   Fri, 3 Nov 2023 12:47:25 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Md Sadre Alam <quic_mdalam@...cinc.com>
Cc:     agross@...nel.org, andersson@...nel.org, konrad.dybcio@...aro.org,
        robh+dt@...nel.org, conor+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, miquel.raynal@...tlin.com,
        richard@....at, vigneshr@...com, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mtd@...ts.infradead.org, linux-spi@...r.kernel.org,
        quic_srichara@...cinc.com, qpic_varada@...cinc.com
Subject: Re: [RFC PATCH 4/5] spi: qpic: Add support for qpic spi nand driver

On Fri, Nov 03, 2023 at 04:50:54PM +0530, Md Sadre Alam wrote:
> On 10/31/2023 7:53 PM, Mark Brown wrote:
> > On Tue, Oct 31, 2023 at 05:33:06PM +0530, Md Sadre Alam wrote:

> > > +	ret = submit_descs(snandc);
> > > +	if (ret)
> > > +		dev_err(snandc->dev, "failure in sbumitting spiinit descriptor\n");
> > > +
> > > +	free_descs(snandc);

> > This seems to be doing a bit more than I would expect an init function
> > to, and it's very surprising to see the descriptors freed immediately
> > after something called a submit (which suggests that the descriptors are
> > still in flight).

> Our controller supports only bam mode , that means for writing/reading even
> single register we have to use bam.
> submit_descs() is synchronous so I/O is complete when it returns.
> Hence freeing the descriptor after it.

That seems like the BAM API is very confusing and error prone.

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