linux-kernel - Re: [PATCH v2 3/9] mfd: cs5535-mfd: Request shared IO regions centrally

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Date:   Mon, 21 Oct 2019 13:46:32 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     Daniel Thompson <daniel.thompson@...aro.org>
Cc:     arnd@...db.de, broonie@...nel.org, linus.walleij@...aro.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        baohua@...nel.org, stephan@...hold.net
Subject: Re: [PATCH v2 3/9] mfd: cs5535-mfd: Request shared IO regions
 centrally

On Mon, 21 Oct 2019, Daniel Thompson wrote:

> On Mon, Oct 21, 2019 at 11:58:16AM +0100, Lee Jones wrote:
> > Prior to this patch, IO regions were requested via an MFD subsytem-level
> > .enable() call-back and similarly released by a .disable() call-back.
> > Double requests/releases were avoided by a centrally handled usage count
> > mechanism.
> > 
> > This complexity can all be avoided by handling IO regions only once during
> > .probe() and .remove() of the parent device.  Since this is the only
> > legitimate user of the aforementioned usage count mechanism, this patch
> > will allow it to be removed from MFD core in subsequent steps.
> > 
> > Suggested-by: Daniel Thompson <daniel.thompson@...aro.org>
> > Signed-off-by: Lee Jones <lee.jones@...aro.org>
> > ---
> >  drivers/mfd/cs5535-mfd.c | 72 +++++++++++++++++-----------------------
> >  1 file changed, 30 insertions(+), 42 deletions(-)
> > 
> > diff --git a/drivers/mfd/cs5535-mfd.c b/drivers/mfd/cs5535-mfd.c
> > index 9ce6bbcdbda1..053e33447808 100644
> > --- a/drivers/mfd/cs5535-mfd.c
> > +++ b/drivers/mfd/cs5535-mfd.c
> > @@ -27,38 +27,6 @@ enum cs5535_mfd_bars {
> >  	NR_BARS,
> >  };
> >  
> > -static int cs5535_mfd_res_enable(struct platform_device *pdev)
> > -{
> > -	struct resource *res;
> > -
> > -	res = platform_get_resource(pdev, IORESOURCE_IO, 0);
> > -	if (!res) {
> > -		dev_err(&pdev->dev, "can't fetch device resource info\n");
> > -		return -EIO;
> > -	}
> > -
> > -	if (!request_region(res->start, resource_size(res), DRV_NAME)) {
> > -		dev_err(&pdev->dev, "can't request region\n");
> > -		return -EIO;
> > -	}
> > -
> > -	return 0;
> > -}
> > -
> > -static int cs5535_mfd_res_disable(struct platform_device *pdev)
> > -{
> > -	struct resource *res;
> > -
> > -	res = platform_get_resource(pdev, IORESOURCE_IO, 0);
> > -	if (!res) {
> > -		dev_err(&pdev->dev, "can't fetch device resource info\n");
> > -		return -EIO;
> > -	}
> > -
> > -	release_region(res->start, resource_size(res));
> > -	return 0;
> > -}
> > -
> >  static struct resource cs5535_mfd_resources[NR_BARS];
> >  
> >  static struct mfd_cell cs5535_mfd_cells[] = {
> > @@ -81,17 +49,11 @@ static struct mfd_cell cs5535_mfd_cells[] = {
> >  		.name = "cs5535-pms",
> >  		.num_resources = 1,
> >  		.resources = &cs5535_mfd_resources[PMS_BAR],
> > -
> > -		.enable = cs5535_mfd_res_enable,
> > -		.disable = cs5535_mfd_res_disable,
> >  	},
> >  	[ACPI_BAR] = {
> >  		.name = "cs5535-acpi",
> >  		.num_resources = 1,
> >  		.resources = &cs5535_mfd_resources[ACPI_BAR],
> > -
> > -		.enable = cs5535_mfd_res_enable,
> > -		.disable = cs5535_mfd_res_disable,
> >  	},
> >  };
> >  
> > @@ -109,7 +71,6 @@ static int cs5535_mfd_probe(struct pci_dev *pdev,
> >  	if (err)
> >  		return err;
> >  
> > -	/* fill in IO range for each cell; subdrivers handle the region */
> >  	for (i = 0; i < NR_BARS; i++) {
> >  		struct mfd_cell *cell = &cs5535_mfd_cells[i];
> >  		struct resource *r = &cs5535_mfd_resources[i];
> > @@ -122,22 +83,47 @@ static int cs5535_mfd_probe(struct pci_dev *pdev,
> >  		r->end = pci_resource_end(pdev, i);
> >  	}
> >  
> > +	err = pci_request_region(pdev, PMS_BAR, DRV_NAME);
> > +	if (err) {
> > +		dev_err(&pdev->dev, "Failed to request PMS_BAR's IO region\n");
> > +		goto err_disable;
> > +	}
> > +
> >  	err = mfd_add_devices(&pdev->dev, PLATFORM_DEVID_NONE, cs5535_mfd_cells,
> >  			      ARRAY_SIZE(cs5535_mfd_cells), NULL, 0, NULL);
> >  	if (err) {
> >  		dev_err(&pdev->dev,
> >  			"Failed to add CS5532 sub-devices: %d\n", err);
> > -		goto err_disable;
> > +		goto err_release_pms;
> >  	}
> >  
> > -	if (machine_is_olpc())
> > -		mfd_clone_cell("cs5535-acpi", olpc_acpi_clones, ARRAY_SIZE(olpc_acpi_clones));
> > +	if (machine_is_olpc()) {
> > +		err = pci_request_region(pdev, ACPI_BAR, DRV_NAME);
> > +		if (err) {
> > +			dev_err(&pdev->dev,
> > +				"Failed to request ACPI_BAR's IO region\n");
> > +			goto err_remove_devices;
> > +		}
> > +
> > +		err = mfd_clone_cell("cs5535-acpi", olpc_acpi_clones,
> > +				     ARRAY_SIZE(olpc_acpi_clones));
> > +		if (err) {
> > +			dev_err(&pdev->dev, "Failed to clone MFD cell\n");
> > +			goto err_release_acpi;
> > +		}
> > +	}
> 
> Making the request_region() conditional on machine_is_olpc() seems to be
> best on the assumption that the cs5535-acpi is not otherwise used.
> 
> I suspect the assumption is true but you have to combine knowledge from
> several bits of code to figure that out.

It is not used.

Will reply to your other comment.

-- 
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
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