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Date: Fri, 19 Jan 2024 21:00:04 -0500
From: Frank Li <Frank.li@nxp.com>
To: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Cc: "ran.wang_1@nxp.com" <ran.wang_1@nxp.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"open  list:DESIGNWARE USB3 DRD IP DRIVER" <linux-usb@vger.kernel.org>,
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	"sergei.shtylyov@cogentembedded.com" <sergei.shtylyov@cogentembedded.com>
Subject: Re: [PATCH 2/2] usb: dwc3: Add workaround for host mode VBUS glitch
 when boot
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References: <20240119213130.3147517-1-Frank.Li@nxp.com>
 <20240119213130.3147517-2-Frank.Li@nxp.com>
 <20240120005056.o52hqn2sershhm76@synopsys.com>
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On Sat, Jan 20, 2024 at 12:51:07AM +0000, Thinh Nguyen wrote:
> On Fri, Jan 19, 2024, Frank Li wrote:
> > From: Ran Wang <ran.wang_1@nxp.com>
> > 
> > When DWC3 is set to host mode by programming register DWC3_GCTL, VBUS
> > (or its control signal) will be turned on immediately on related Root Hub
> > ports. Then, the VBUS is turned off for a little while(15us) when do xhci
> > reset (conducted by xhci driver) and back to normal finally, we can
> > observe a negative glitch of related signal happen.
> > 
> > This VBUS glitch might cause some USB devices enumeration fail if kernel
> > boot with them connected. Such as LS1012AFWRY/LS1043ARDB/LX2160AQDS
> > /LS1088ARDB with Kingston 16GB USB2.0/Kingston USB3.0/JetFlash Transcend
> > 4GB USB2.0 drives. The fail cases include enumerated as full-speed device
> > or report wrong device descriptor, etc.
> > 
> > One SW workaround which can fix this is by programing all xhci PORTSC[PP]
> > to 0 to turn off VBUS immediately after setting host mode in DWC3 driver
> > (per signal measurement result, it will be too late to do it in
> > xhci-plat.c or xhci.c). Then, after xhci reset complete in xhci driver,
> > PORTSC[PP]s' value will back to 1 automatically and VBUS on at that time,
> > no glitch happen and normal enumeration process has no impact.
> > 
> > Signed-off-by: Ran Wang <ran.wang_1@nxp.com>
> > Reviewed-by: Peter Chen <peter.chen@nxp.com>
> > Signed-off-by: Frank Li <Frank.Li@nxp.com>
> > ---
> > 
> > Notes:
> >     Last review at June 06, 2019. Fixed all review comments and sent again.
> >     
> >     https://urldefense.com/v3/__https://lore.kernel.org/linux-kernel/AM5PR0402MB2865979E26017BC5937DBBA5F1170@AM5PR0402MB2865.eurprd04.prod.outlook.com/__;!!A4F2R9G_pg!bdutJWi1Tcz8SYscB7Mr96SWYMKIo8ElUKgEILFJfK3_60EbECQHXPBmJYAMMhNwQ4YrjxqMZWHdokXhHB6a$ 
> > 
> >  drivers/usb/dwc3/core.c |  2 ++
> >  drivers/usb/dwc3/core.h |  2 ++
> >  drivers/usb/dwc3/host.c | 46 +++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 50 insertions(+)
> > 
> > diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> > index 3e55838c00014..a57adf0c11dd1 100644
> > --- a/drivers/usb/dwc3/core.c
> > +++ b/drivers/usb/dwc3/core.c
> > @@ -1626,6 +1626,8 @@ static void dwc3_get_properties(struct dwc3 *dwc)
> >  	dwc->dis_split_quirk = device_property_read_bool(dev,
> >  				"snps,dis-split-quirk");
> >  
> > +	dwc->host_vbus_glitches = device_property_read_bool(dev, "snps,host-vbus-glitches");
> 
> This is a quirk. The property should be named with "quirk" subfix.
> But do we need a new quirk? How many different platforms are affected?
> If it's just 1 or 2, then just use compatible string.

more than 2 platform. I think quirk is more flexible.

Frank
> 
> > +
> >  	dwc->lpm_nyet_threshold = lpm_nyet_threshold;
> >  	dwc->tx_de_emphasis = tx_de_emphasis;
> >  
> > diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
> > index e3eea965e57bf..0269bacbbf6bd 100644
> > --- a/drivers/usb/dwc3/core.h
> > +++ b/drivers/usb/dwc3/core.h
> > @@ -1135,6 +1135,7 @@ struct dwc3_scratchpad_array {
> >   * @dis_split_quirk: set to disable split boundary.
> >   * @wakeup_configured: set if the device is configured for remote wakeup.
> >   * @suspended: set to track suspend event due to U3/L2.
> > + * @host_vbus_glitches: set to avoid vbus glitch during xhci reset.
> 
> This is only applicable to the first xhci reset in its initialization
> and not every xhci reset right? If so, please reword.
> 
> Also, please place it correspond to the order of the field.
> 
> >   * @imod_interval: set the interrupt moderation interval in 250ns
> >   *			increments or 0 to disable.
> >   * @max_cfg_eps: current max number of IN eps used across all USB configs.
> > @@ -1353,6 +1354,7 @@ struct dwc3 {
> >  	unsigned		tx_de_emphasis:2;
> >  
> >  	unsigned		dis_metastability_quirk:1;
> > +	unsigned		host_vbus_glitches:1;
> >  
> >  	unsigned		dis_split_quirk:1;
> >  	unsigned		async_callbacks:1;
> > diff --git a/drivers/usb/dwc3/host.c b/drivers/usb/dwc3/host.c
> > index 61f57fe5bb783..af8903ee37c20 100644
> > --- a/drivers/usb/dwc3/host.c
> > +++ b/drivers/usb/dwc3/host.c
> > @@ -11,6 +11,7 @@
> >  #include <linux/of.h>
> >  #include <linux/platform_device.h>
> >  
> > +#include "../host/xhci.h"
> 
> Let's not import the entire xhci.h. If we're going to share some macros
> from xhci.h, please split them from xhci.h and perhaps create
> xhci-ports.h for dwc3 to share.
> 
> >  #include "core.h"
> >  
> >  static void dwc3_host_fill_xhci_irq_res(struct dwc3 *dwc,
> > @@ -28,6 +29,44 @@ static void dwc3_host_fill_xhci_irq_res(struct dwc3 *dwc,
> >  		dwc->xhci_resources[1].name = name;
> >  }
> >  
> > +#define XHCI_HCSPARAMS1		0x4
> > +#define XHCI_PORTSC_BASE	0x400
> > +
> > +/*
> > + * dwc3_power_off_all_roothub_ports - Power off all Root hub ports
> > + * @dwc3: Pointer to our controller context structure
> > + */
> > +static void dwc3_power_off_all_roothub_ports(struct dwc3 *dwc)
> > +{
> > +	int i, port_num;
> > +	u32 reg, op_regs_base, offset;
> > +	void __iomem *xhci_regs;
> > +
> > +	/* xhci regs is not mapped yet, do it temperary here */
> > +	if (dwc->xhci_resources[0].start) {
> > +		xhci_regs = ioremap(dwc->xhci_resources[0].start,
> > +				DWC3_XHCI_REGS_END);
> > +		if (IS_ERR(xhci_regs)) {
> > +			dev_err(dwc->dev, "Failed to ioremap xhci_regs\n");
> > +			return;
> > +		}
> > +
> > +		op_regs_base = HC_LENGTH(readl(xhci_regs));
> > +		reg = readl(xhci_regs + XHCI_HCSPARAMS1);
> > +		port_num = HCS_MAX_PORTS(reg);
> > +
> > +		for (i = 1; i <= port_num; i++) {
> > +			offset = op_regs_base + XHCI_PORTSC_BASE + 0x10*(i-1);
> > +			reg = readl(xhci_regs + offset);
> > +			reg &= ~PORT_POWER;
> > +			writel(reg, xhci_regs + offset);
> > +		}
> > +
> > +		iounmap(xhci_regs);
> > +	} else
> > +		dev_err(dwc->dev, "xhci base reg invalid\n");
> > +}
> > +
> >  static int dwc3_host_get_irq(struct dwc3 *dwc)
> >  {
> >  	struct platform_device	*dwc3_pdev = to_platform_device(dwc->dev);
> > @@ -66,6 +105,13 @@ int dwc3_host_init(struct dwc3 *dwc)
> >  	int			ret, irq;
> >  	int			prop_idx = 0;
> >  
> > +	/*
> > +	 * We have to power off all Root hub ports immediately after DWC3 set
> > +	 * to host mode to avoid VBUS glitch happen when xhci get reset later.
> > +	 */
> > +	if (dwc->host_vbus_glitches)
> > +		dwc3_power_off_all_roothub_ports(dwc);
> > +
> 
> It's part of the dwc3_host_init(), but don't do this in
> dwc3_host_get_irq(). Place it where it makes sense.
> 
> >  	irq = dwc3_host_get_irq(dwc);
> >  	if (irq < 0)
> >  		return irq;
> > -- 
> > 2.34.1
> > 
> 
> Please run checkpatch.pl and fix them next time. Regarding
> PARENTHESIS_ALIGNMENT or line continuation, it can be two indentations
> or parenthesis aligned, whichever one makes it easier to read.
> 
> 
> From checkpatch:
> 
> CHECK:PARENTHESIS_ALIGNMENT: Alignment should match open parenthesis
> #119: FILE: drivers/usb/dwc3/host.c:48:
> +		xhci_regs = ioremap(dwc->xhci_resources[0].start,
> +				DWC3_XHCI_REGS_END);
> 
> CHECK:SPACING: spaces preferred around that '*' (ctx:VxV)
> #130: FILE: drivers/usb/dwc3/host.c:59:
> +			offset = op_regs_base + XHCI_PORTSC_BASE + 0x10*(i-1);
>  			                                               ^
> 
> CHECK:SPACING: spaces preferred around that '-' (ctx:VxV)
> #130: FILE: drivers/usb/dwc3/host.c:59:
> +			offset = op_regs_base + XHCI_PORTSC_BASE + 0x10*(i-1);
>  			                                                  ^
> 
> CHECK:BRACES: Unbalanced braces around else statement
> #137: FILE: drivers/usb/dwc3/host.c:66:
> +	} else
> 

Sorry, I too trust original patch author. Will fix next version

Frank

> total: 0 errors, 0 warnings, 4 checks, 86 lines checked
> 
> 
> Thanks,
> Thinh