linux-kernel - Re: [PATCH v2 2/6] reset: qcom: PDC Global (Power Domain Controller) reset controller

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Message-ID: <20180828165619.GA10879@google.com>
Date:   Tue, 28 Aug 2018 09:56:19 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Sibi Sankar <sibis@...eaurora.org>, p.zabel@...gutronix.de,
        robh+dt@...nel.org, linux-remoteproc@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        ohad@...ery.com, mark.rutland@....com, sricharan@...eaurora.org,
        akdwived@...eaurora.org, linux-arm-msm@...r.kernel.org,
        tsoni@...eaurora.org
Subject: Re: [PATCH v2 2/6] reset: qcom: PDC Global (Power Domain Controller)
 reset controller

On Mon, Aug 27, 2018 at 08:02:53PM -0700, Bjorn Andersson wrote:
> On Mon 27 Aug 17:22 PDT 2018, Matthias Kaehlcke wrote:
> > On Fri, Aug 24, 2018 at 06:48:56PM +0530, Sibi Sankar wrote:
> > > diff --git a/drivers/reset/reset-qcom-pdc.c b/drivers/reset/reset-qcom-pdc.c
> [..]
> > > +struct qcom_pdc_desc {
> > > +	const struct regmap_config *config;
> > > +	const struct qcom_pdc_reset_map *resets;
> > > +	size_t num_resets;
> > > +};
> > 
> > Not sure if this structure adds much value or just a layer of
> > indirection:
> > 
> > - .config is only accessed in _probe(), sdm845_pdc_regmap_config could
> >   be used directly
> > - .resets is used in _(de)assert(), sdm845_pdc_resets could be used
> >   directly
> > - .num_resets is only accessed in _probe(),
> >   ARRAY_SIZE(sdm845_pdc_resets) could be used instead
> > 
> > It probably makes sense if it is planned to support reset controllers
> > of other SoCs with this driver.
> > 
> 
> I like this suggestion, once we need the configurability we can add the
> type for it. It also shows that only .resets would need to be referenced
> by qcom_pdc_reset_data.
> 
> > > +struct qcom_pdc_reset_data {
> > > +	struct reset_controller_dev rcdev;
> > > +	struct regmap *regmap;
> > > +	const struct qcom_pdc_desc *desc;
> > > +};
> [..]
> > > +static int qcom_pdc_reset_probe(struct platform_device *pdev)
> > > +{
> [..]
> > > +	data->regmap = devm_regmap_init_mmio(dev, base, desc->config);
> > > +	if (IS_ERR(data->regmap)) {
> > > +		dev_err(dev, "Unable to get pdc-global regmap");
> > 
> > Add missing '\n'
> > 
> > Say 'pdc-reset' instead of 'pdc-global'? (see also my other comment
> > below).
> > 
> 
> This regmap is created out of the single anonymous "reg", so I think the
> error should be reduced to "Unable to initialize regmap\n".
> 
> [..]
> > > +static const struct of_device_id qcom_pdc_reset_of_match[] = {
> > > +	{ .compatible = "qcom,sdm845-pdc-global", .data = &sdm845_pdc_desc },
> > 
> > Should this be 'qcom,sdm845-pdc-reset' which is more specific than
> > 'global' and in line with the name and purpose of the driver?
> > Obviously this would require to adjust the bindings doc too.
> > 
> 
> No, the binding describes the hardware block named "PDC Global",
> currently implemented as a reset controller. The reason for doing this
> is so that we one day can expose additional interfaces in a backwards
> compatible fashion.

Sounds reasonable, thanks for the clarification.