Subject: Re: [PATCH V2] net: stmmac: socfpga: Remove re-registration of reset controller

From: Dinh Nguyen <[email-masked]>
Date: Wed, 20 Apr 2016 21:44:11 -0500

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 <[email-masked]>
>>> Cc: Matthew Gerlach <[email-masked]>
>>> Cc: Dinh Nguyen <[email-masked]>
>>> Cc: David S. Miller <[email-masked]>
>>> ---
>>> 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.

So yes, please spin V3.

Thanks,
Dinh