Date:	Thu, 21 Apr 2016 13:51:55 +0200
From:	Marek Vasut <marex@...x.de>
To:	Dinh Nguyen <dinguyen@...nsource.altera.com>,
	netdev@...r.kernel.org
CC:	peppe.cavallaro@...com, alexandre.torgue@...com,
	Matthew Gerlach <mgerlach@...nsource.altera.com>,
	"David S . Miller" <davem@...emloft.net>
Subject: Re: [PATCH V2] net: stmmac: socfpga: Remove re-registration of reset
 controller

On 04/21/2016 04:44 AM, Dinh Nguyen wrote:
> 
> 
> On 04/20/2016 05:27 PM, Marek Vasut wrote:
>> On 04/20/2016 11:17 PM, Dinh Nguyen wrote:
>>> On 04/19/2016 07:05 PM, Marek Vasut wrote:
>>>> Both socfpga_dwmac_parse_data() in dwmac-socfpga.c and stmmac_dvr_probe()
>>>> in stmmac_main.c functions call devm_reset_control_get() to register an
>>>> reset controller for the stmmac. This results in an attempt to register
>>>> two reset controllers for the same non-shared reset line.
>>>>
>>>> The first attempt to register the reset controller works fine. The second
>>>> attempt fails with warning from the reset controller core, see below.
>>>> The warning is produced because the reset line is non-shared and thus
>>>> it is allowed to have only up-to one reset controller associated with
>>>> that reset line, not two or more.
>>>>
>>>> The solution is not great. Since the hardware needs to toggle the reset
>>>> before calling stmmac_dvr_probe() to perform mandatory preconfiguration,
>>>> this patch splits socfpga_dwmac_init_probe() from socfpga_dwmac_init().
>>>>
>>>> The socfpga_dwmac_init_probe() temporarily registers the reset controller,
>>>> performs the pre-configuration and unregisters the reset controller again.
>>>> This function is only called from the socfpga_dwmac_probe().
>>>>
>>>> The original socfpga_dwmac_init() is tweaked to use reset controller
>>>> pointer from the stmmac_priv (private data of the stmmac core) instead
>>>> of the local instance, which was used before.
>>>>
>>>> Finally, plat_dat->exit and socfpga_dwmac_exit() is no longer necessary,
>>>> since the functionality is already performed by the stmmac core.
>>>>
>>>> ------------[ cut here ]------------
>>>> WARNING: CPU: 0 PID: 1 at drivers/reset/core.c:187 __of_reset_control_get+0x218/0x270
>>>> Modules linked in:
>>>> CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.6.0-rc4-next-20160419-00015-gabb2477-dirty #4
>>>> Hardware name: Altera SOCFPGA
>>>> [<c010f290>] (unwind_backtrace) from [<c010b82c>] (show_stack+0x10/0x14)
>>>> [<c010b82c>] (show_stack) from [<c0373da4>] (dump_stack+0x94/0xa8)
>>>> [<c0373da4>] (dump_stack) from [<c011bcc0>] (__warn+0xec/0x104)
>>>> [<c011bcc0>] (__warn) from [<c011bd88>] (warn_slowpath_null+0x20/0x28)
>>>> [<c011bd88>] (warn_slowpath_null) from [<c03a6eb4>] (__of_reset_control_get+0x218/0x270)
>>>> [<c03a6eb4>] (__of_reset_control_get) from [<c03a701c>] (__devm_reset_control_get+0x54/0x90)
>>>> [<c03a701c>] (__devm_reset_control_get) from [<c041fa30>] (stmmac_dvr_probe+0x1b4/0x8e8)
>>>> [<c041fa30>] (stmmac_dvr_probe) from [<c04298c8>] (socfpga_dwmac_probe+0x1b8/0x28c)
>>>> [<c04298c8>] (socfpga_dwmac_probe) from [<c03d6ffc>] (platform_drv_probe+0x4c/0xb0)
>>>> [<c03d6ffc>] (platform_drv_probe) from [<c03d54ec>] (driver_probe_device+0x224/0x2bc)
>>>> [<c03d54ec>] (driver_probe_device) from [<c03d5630>] (__driver_attach+0xac/0xb0)
>>>> [<c03d5630>] (__driver_attach) from [<c03d382c>] (bus_for_each_dev+0x6c/0xa0)
>>>> [<c03d382c>] (bus_for_each_dev) from [<c03d4ad4>] (bus_add_driver+0x1a4/0x21c)
>>>> [<c03d4ad4>] (bus_add_driver) from [<c03d60ac>] (driver_register+0x78/0xf8)
>>>> [<c03d60ac>] (driver_register) from [<c0101760>] (do_one_initcall+0x40/0x170)
>>>> [<c0101760>] (do_one_initcall) from [<c0800e38>] (kernel_init_freeable+0x1dc/0x27c)
>>>> [<c0800e38>] (kernel_init_freeable) from [<c05d1bd4>] (kernel_init+0x8/0x114)
>>>> [<c05d1bd4>] (kernel_init) from [<c01076f8>] (ret_from_fork+0x14/0x3c)
>>>> ---[ end trace 059d2fbe87608fa9 ]---
>>>>
>>>> Signed-off-by: Marek Vasut <marex@...x.de>
>>>> Cc: Matthew Gerlach <mgerlach@...nsource.altera.com>
>>>> Cc: Dinh Nguyen <dinguyen@...nsource.altera.com>
>>>> Cc: David S. Miller <davem@...emloft.net>
>>>> ---
>>>> V2: Add missing stmmac_rst = NULL; into socfpga_dwmac_init_probe()
>>>> ---
>>>>  .../net/ethernet/stmicro/stmmac/dwmac-socfpga.c    | 70 ++++++++++++----------
>>>>  1 file changed, 39 insertions(+), 31 deletions(-)
>>>>
>>>> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-socfpga.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-socfpga.c
>>>> index 76d671e..5885a2e 100644
>>>> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac-socfpga.c
>>>> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-socfpga.c
>>>> @@ -49,7 +49,6 @@ struct socfpga_dwmac {
>>>>  	u32	reg_shift;
>>>>  	struct	device *dev;
>>>>  	struct regmap *sys_mgr_base_addr;
>>>> -	struct reset_control *stmmac_rst;
>>>>  	void __iomem *splitter_base;
>>>>  	bool f2h_ptp_ref_clk;
>>>>  };
>>>> @@ -92,15 +91,6 @@ static int socfpga_dwmac_parse_data(struct socfpga_dwmac *dwmac, struct device *
>>>>  	struct device_node *np_splitter;
>>>>  	struct resource res_splitter;
>>>>  
>>>> -	dwmac->stmmac_rst = devm_reset_control_get(dev,
>>>> -						  STMMAC_RESOURCE_NAME);
>>>> -	if (IS_ERR(dwmac->stmmac_rst)) {
>>>> -		dev_info(dev, "Could not get reset control!\n");
>>>> -		if (PTR_ERR(dwmac->stmmac_rst) == -EPROBE_DEFER)
>>>> -			return -EPROBE_DEFER;
>>>> -		dwmac->stmmac_rst = NULL;
>>>> -	}
>>>> -
>>>>  	dwmac->interface = of_get_phy_mode(np);
>>>>  
>>>>  	sys_mgr_base_addr = syscon_regmap_lookup_by_phandle(np, "altr,sysmgr-syscon");
>>>> @@ -194,30 +184,23 @@ static int socfpga_dwmac_setup(struct socfpga_dwmac *dwmac)
>>>>  	return 0;
>>>>  }
>>>>  
>>>> -static void socfpga_dwmac_exit(struct platform_device *pdev, void *priv)
>>>> -{
>>>> -	struct socfpga_dwmac	*dwmac = priv;
>>>> -
>>>> -	/* On socfpga platform exit, assert and hold reset to the
>>>> -	 * enet controller - the default state after a hard reset.
>>>> -	 */
>>>> -	if (dwmac->stmmac_rst)
>>>> -		reset_control_assert(dwmac->stmmac_rst);
>>>> -}
>>>> -
>>>>  static int socfpga_dwmac_init(struct platform_device *pdev, void *priv)
>>>>  {
>>>> -	struct socfpga_dwmac	*dwmac = priv;
>>>> +	struct socfpga_dwmac *dwmac = priv;
>>>>  	struct net_device *ndev = platform_get_drvdata(pdev);
>>>>  	struct stmmac_priv *stpriv = NULL;
>>>>  	int ret = 0;
>>>>  
>>>> -	if (ndev)
>>>> -		stpriv = netdev_priv(ndev);
>>>> +	if (!ndev)
>>>> +		return -EINVAL;
>>>> +
>>>> +	stpriv = netdev_priv(ndev);
>>>> +	if (!stpriv)
>>>> +		return -EINVAL;
>>>>  
>>>>  	/* Assert reset to the enet controller before changing the phy mode */
>>>> -	if (dwmac->stmmac_rst)
>>>> -		reset_control_assert(dwmac->stmmac_rst);
>>>> +	if (stpriv->stmmac_rst)
>>>> +		reset_control_assert(stpriv->stmmac_rst);
>>>>  
>>>>  	/* Setup the phy mode in the system manager registers according to
>>>>  	 * devicetree configuration
>>>> @@ -227,8 +210,8 @@ static int socfpga_dwmac_init(struct platform_device *pdev, void *priv)
>>>>  	/* Deassert reset for the phy configuration to be sampled by
>>>>  	 * the enet controller, and operation to start in requested mode
>>>>  	 */
>>>> -	if (dwmac->stmmac_rst)
>>>> -		reset_control_deassert(dwmac->stmmac_rst);
>>>> +	if (stpriv->stmmac_rst)
>>>> +		reset_control_deassert(stpriv->stmmac_rst);
>>>>  
>>>>  	/* Before the enet controller is suspended, the phy is suspended.
>>>>  	 * This causes the phy clock to be gated. The enet controller is
>>>> @@ -245,12 +228,38 @@ static int socfpga_dwmac_init(struct platform_device *pdev, void *priv)
>>>>  	 * control register 0, and can be modified by the phy driver
>>>>  	 * framework.
>>>>  	 */
>>>> -	if (stpriv && stpriv->phydev)
>>>> +	if (stpriv->phydev)
>>>>  		phy_resume(stpriv->phydev);
>>>>  
>>>>  	return ret;
>>>>  }
>>>>  
>>>> +static int socfpga_dwmac_init_probe(struct socfpga_dwmac *dwmac)
>>>> +{
>>>> +	struct reset_control *stmmac_rst;
>>>> +	int ret;
>>>> +
>>>> +	stmmac_rst = reset_control_get(dwmac->dev, STMMAC_RESOURCE_NAME);
>>>> +	if (IS_ERR(stmmac_rst)) {
>>>> +		dev_info(dwmac->dev, "Could not get reset control!\n");
>>>> +		if (PTR_ERR(stmmac_rst) == -EPROBE_DEFER)
>>>> +			return -EPROBE_DEFER;
>>>> +		stmmac_rst = NULL;
>>>> +	}
>>>> +
>>>> +	if (stmmac_rst)
>>>> +		reset_control_assert(stmmac_rst);
>>>> +
>>>> +	ret = socfpga_dwmac_setup(dwmac);
>>>> +
>>>> +	if (stmmac_rst) {
>>>> +		reset_control_deassert(stmmac_rst);
>>>> +		reset_control_put(stmmac_rst);
>>>> +	}
>>>> +
>>>> +	return ret;
>>>> +}
>>>
>>> I don't think you this function because...
>>>
>>>> +
>>>>  static int socfpga_dwmac_probe(struct platform_device *pdev)
>>>>  {
>>>>  	struct plat_stmmacenet_data *plat_dat;
>>>> @@ -279,10 +288,9 @@ static int socfpga_dwmac_probe(struct platform_device *pdev)
>>>>  
>>>>  	plat_dat->bsp_priv = dwmac;
>>>>  	plat_dat->init = socfpga_dwmac_init;
>>>> -	plat_dat->exit = socfpga_dwmac_exit;
>>>>  	plat_dat->fix_mac_speed = socfpga_dwmac_fix_mac_speed;
>>>>  
>>>> -	ret = socfpga_dwmac_init(pdev, plat_dat->bsp_priv);
>>>> +	ret = socfpga_dwmac_init_probe(dwmac);
>>>>  	if (ret)
>>>>  		return ret;
>>>>  
>>>>
>>>
>>> if you modify the patch to call stmmac_dvr_probe() before calling
>>> socfpga_dwmac_init(), then you would already have the reset control
>>> information.
>>
>> I was under the impression that you must call socfpga_dwmac_init()
>> before stmmac_dvr_probe() for whatever hardware-related reason. If
>> you are absolutely certain this is not necessary, then that's just
>> perfect and the patch can be simplified even further -- just remove
>> the call to socfpga_dwmac_init() from probe altogether , the dwmac
>> core code will call plat_dat->init at the end of probe .
>>
>> So shall we do that ? I am happy to spin V3 like that if you confirm
>> that it's legal to do things in the aforementioned order.
>>
> 
> AFAICT, I don't see any reason why the socfpga_dwmac_init() has to go
> before the stmmac_dvr_probe(). I tested this by using U-Boot to put the
> PHY modes in the system manager into a different mode, and put the
> ethernet IP into reset. Linux was able to use ethernet just fine with
> the aformentioned order.

Ha, the dwmac code does not call the ->init, so you have to call it from
the socfpga-dwmac probe afterall. I will send a V3 now and do
it just like you suggested. I will send a RFC for calling ->init and
->exit from the stmmac common code too.

> So yes, please spin V3.
> 
> Thanks,
> Dinh
> 


-- 
Best regards,
Marek Vasut

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