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

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Message-ID: <56975E5D.50603@ti.com>
Date:	Thu, 14 Jan 2016 14:07:49 +0530
From:	Kishon Vijay Abraham I <kishon@...com>
To:	Suman Anna <s-anna@...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

Hi Suman,

On Wednesday 13 January 2016 11:21 PM, Suman Anna wrote:
> 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.

hmm.. not sure of the benefits of leaving the reset lines de-asserted during
remove. The idea is irrespective of the initial sate or power-on state, during
probe the driver should assert and de-assert the reset lines.

Thanks
Kishon