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

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Message-ID: <20191021122606.5q22j6wtyslwljco@holly.lan>
Date:   Mon, 21 Oct 2019 13:26:06 +0100
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Lee Jones <lee.jones@...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, 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.


Daniel.


>  
>  	dev_info(&pdev->dev, "%zu devices registered.\n",
>  			ARRAY_SIZE(cs5535_mfd_cells));
>  
>  	return 0;
>  
> +err_release_acpi:
> +	pci_release_region(pdev, ACPI_BAR);
> +err_remove_devices:
> +	mfd_remove_devices(&pdev->dev);
> +err_release_pms:
> +	pci_release_region(pdev, PMS_BAR);
>  err_disable:
>  	pci_disable_device(pdev);
>  	return err;
> @@ -145,6 +131,8 @@ static int cs5535_mfd_probe(struct pci_dev *pdev,
>  
>  static void cs5535_mfd_remove(struct pci_dev *pdev)
>  {
> +	pci_release_region(pdev, PMS_BAR);
> +	pci_release_region(pdev, ACPI_BAR);
>  	mfd_remove_devices(&pdev->dev);
>  	pci_disable_device(pdev);
>  }
> -- 
> 2.17.1
>