linux-kernel - Re: [PATCH v2 3/3] pci: dra7xx: use pdata callbacks to perform reset

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Date:	Wed, 13 Jan 2016 11:51:34 -0600
From:	Suman Anna <s-anna@...com>
To:	Kishon Vijay Abraham I <kishon@...com>,
	Tony Lindgren <tony@...mide.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>, <richardcochran@...il.com>
CC:	Russell King <linux@....linux.org.uk>,
	<linux-omap@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <nsekhar@...com>
Subject: Re: [PATCH v2 3/3] pci: dra7xx: use pdata callbacks to perform reset

On 01/13/2016 12:47 AM, Kishon Vijay Abraham I wrote:
> Use platform populated reset assert and deassert
> callbacks to perform reset of PCIe.
> 
> Use these callbacks until a reset interface using drivers/reset
> is available for the purpose.
> 
> Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
> Signed-off-by: Sekhar Nori <nsekhar@...com>
> ---
>  drivers/pci/host/pci-dra7xx.c |   32 ++++++++++++++++++++++++++++++++
>  1 file changed, 32 insertions(+)
> 
> diff --git a/drivers/pci/host/pci-dra7xx.c b/drivers/pci/host/pci-dra7xx.c
> index 8c36880..049083d 100644
> --- a/drivers/pci/host/pci-dra7xx.c
> +++ b/drivers/pci/host/pci-dra7xx.c
> @@ -25,6 +25,8 @@
>  #include <linux/resource.h>
>  #include <linux/types.h>
>  
> +#include <linux/platform_data/pci-dra7xx.h>
> +
>  #include "pcie-designware.h"
>  
>  /* PCIe controller wrapper DRA7XX configuration registers */
> @@ -329,6 +331,32 @@ static int __init dra7xx_add_pcie_port(struct dra7xx_pcie *dra7xx,
>  	return 0;
>  }
>  
> +static int dra7xx_pcie_reset(struct platform_device *pdev)
> +{
> +	int ret;
> +	struct device *dev = &pdev->dev;
> +	struct pci_dra7xx_platform_data *pdata = pdev->dev.platform_data;
> +
> +	if (!(pdata && pdata->deassert_reset && pdata->assert_reset)) {
> +		dev_err(dev, "platform data for reset not found!\n");
> +		return -EINVAL;
> +	}
> +
> +	ret = pdata->assert_reset(pdev, pdata->reset_name);
> +	if (ret) {
> +		dev_err(dev, "assert_reset failed: %d\n", ret);
> +		return ret;
> +	}
> +
> +	ret = pdata->deassert_reset(pdev, pdata->reset_name);
> +	if (ret) {
> +		dev_err(dev, "deassert_reset failed: %d\n", ret);
> +		return ret;
> +	}

The only comment I have on this is the symmetry (assert_reset invocation
in driver remove). If you install and remove the module once, then the
reset stays deasserted. On Power-On-Reset, the resets by default will be
in asserted state.

regards
SUman

> +
> +	return 0;
> +}
> +
>  static int __init dra7xx_pcie_probe(struct platform_device *pdev)
>  {
>  	u32 reg;
> @@ -347,6 +375,10 @@ static int __init dra7xx_pcie_probe(struct platform_device *pdev)
>  	enum of_gpio_flags flags;
>  	unsigned long gpio_flags;
>  
> +	ret = dra7xx_pcie_reset(pdev);
> +	if (ret)
> +		return ret;
> +
>  	dra7xx = devm_kzalloc(dev, sizeof(*dra7xx), GFP_KERNEL);
>  	if (!dra7xx)
>  		return -ENOMEM;
>