[PATCH v1] usb: xhci: allow imod-interval to be configurable

[PATCH v1] usb: xhci: allow imod-interval to be configurable

[Adam Wallis]

The xHCI driver currently has the IMOD set to 160, which
translates to an IMOD interval of 40,000ns (160 * 250)ns

Commit 0cbd4b34cda9 ("xhci: mediatek: support MTK xHCI host controller")
introduced a QUIRK for the MTK platform to adjust this interval to 20,
which translates to an IMOD interval of 5,000ns (20 * 250)ns. This is
due to the fact that the MTK controller IMOD interval is 8 times
as much as defined in xHCI spec.

Instead of adding more quirk bits for additional platforms, this patch
introduces the ability for vendors to set the IMOD_INTERVAL as is
optimal for their platform. By using device_property_read_u32() on
"imod-interval", the IMOD INTERVAL can be specified in nano seconds. If
no interval is specified, the default of 40,000ns (IMOD=160) will be
used.

No bounds checking has been implemented due to the fact that a vendor
may have violated the spec and would need to specify a value outside of
the max 8,000 IRQs/second limit specified in the xHCI spec.

Backwards compatibility is maintained for MTK_HOSTS through the quirk
bit, however, imod_interval should be pushed into device tree at a
future point and this quirk should be removed from xhci_plat_probe

Signed-off-by: Adam Wallis <awallis-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
---
 Documentation/devicetree/bindings/usb/usb-xhci.txt |  1 +
 drivers/usb/host/xhci-plat.c                       | 15 +++++++++++++++
 drivers/usb/host/xhci.c                            |  7 ++-----
 drivers/usb/host/xhci.h                            |  2 ++
 4 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/Documentation/devicetree/bindings/usb/usb-xhci.txt b/Documentation/devicetree/bindings/usb/usb-xhci.txt
index ae6e484..3998459 100644
--- a/Documentation/devicetree/bindings/usb/usb-xhci.txt
+++ b/Documentation/devicetree/bindings/usb/usb-xhci.txt
@@ -29,6 +29,7 @@ Optional properties:
   - usb2-lpm-disable: indicate if we don't want to enable USB2 HW LPM
   - usb3-lpm-capable: determines if platform is USB3 LPM capable
   - quirk-broken-port-ped: set if the controller has broken port disable mechanism
+  - imod-interval: IMOD_INTERVAL in nano-seconds. Default is 40000
 
 Example:
 	usb@f0931000 {
diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
index 09f164f..f7730c8 100644
--- a/drivers/usb/host/xhci-plat.c
+++ b/drivers/usb/host/xhci-plat.c
@@ -23,6 +23,7 @@
 #include "xhci-plat.h"
 #include "xhci-mvebu.h"
 #include "xhci-rcar.h"
+#include "xhci-mtk.h"
 
 static struct hc_driver __read_mostly xhci_plat_hc_driver;
 
@@ -269,6 +270,20 @@ static int xhci_plat_probe(struct platform_device *pdev)
 	if (device_property_read_bool(&pdev->dev, "quirk-broken-port-ped"))
 		xhci->quirks |= XHCI_BROKEN_PORT_PED;
 
+	/* imod interval in nanoseconds */
+	if (device_property_read_u32(sysdev,
+		"imod-interval", &xhci->imod_interval))
+		xhci->imod_interval = 40000;
+	else if (xhci->quirks & XHCI_MTK_HOST)
+		/*
+		 * The increment interval is 8 times as much as that defined in
+		 * the xHCI spec on MTK's controller. This is added to provide
+		 * backwards compatibility, however, this should be pushed into
+		 * the device tree files at some point in the future and
+		 * removed from xhci_plat_probe
+		 */
+		xhci->imod_interval = 5000;
+
 	hcd->usb_phy = devm_usb_get_phy_by_phandle(sysdev, "usb-phy", 0);
 	if (IS_ERR(hcd->usb_phy)) {
 		ret = PTR_ERR(hcd->usb_phy);
diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 2424d30..6a09311 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -586,11 +586,8 @@ int xhci_run(struct usb_hcd *hcd)
 			"// Set the interrupt modulation register");
 	temp = readl(&xhci->ir_set->irq_control);
 	temp &= ~ER_IRQ_INTERVAL_MASK;
-	/*
-	 * the increment interval is 8 times as much as that defined
-	 * in xHCI spec on MTK's controller
-	 */
-	temp |= (u32) ((xhci->quirks & XHCI_MTK_HOST) ? 20 : 160);
+	temp |= (u16) (xhci->imod_interval / 250);
+
 	writel(temp, &xhci->ir_set->irq_control);
 
 	/* Set the HCD state before we enable the irqs */
diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
index 99a014a..2a4177b 100644
--- a/drivers/usb/host/xhci.h
+++ b/drivers/usb/host/xhci.h
@@ -1717,6 +1717,8 @@ struct xhci_hcd {
 	u8		max_interrupters;
 	u8		max_ports;
 	u8		isoc_threshold;
+	/* imod_interval in ns (I * 250ns) */
+	u32		imod_interval;
 	int		event_ring_max;
 	/* 4KB min, 128MB max */
 	int		page_size;
-- 
Qualcomm Datacenter Technologies as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.

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Re: [PATCH v1] usb: xhci: allow imod-interval to be configurable

[Greg Kroah-Hartman]

On Tue, Nov 28, 2017 at 12:11:46PM -0500, Adam Wallis wrote:
> The xHCI driver currently has the IMOD set to 160, which
> translates to an IMOD interval of 40,000ns (160 * 250)ns
> 
> Commit 0cbd4b34cda9 ("xhci: mediatek: support MTK xHCI host controller")
> introduced a QUIRK for the MTK platform to adjust this interval to 20,
> which translates to an IMOD interval of 5,000ns (20 * 250)ns. This is
> due to the fact that the MTK controller IMOD interval is 8 times
> as much as defined in xHCI spec.
> 
> Instead of adding more quirk bits for additional platforms, this patch
> introduces the ability for vendors to set the IMOD_INTERVAL as is
> optimal for their platform. By using device_property_read_u32() on
> "imod-interval", the IMOD INTERVAL can be specified in nano seconds. If
> no interval is specified, the default of 40,000ns (IMOD=160) will be
> used.
> 
> No bounds checking has been implemented due to the fact that a vendor
> may have violated the spec and would need to specify a value outside of
> the max 8,000 IRQs/second limit specified in the xHCI spec.
> 
> Backwards compatibility is maintained for MTK_HOSTS through the quirk
> bit, however, imod_interval should be pushed into device tree at a
> future point and this quirk should be removed from xhci_plat_probe
> 
> Signed-off-by: Adam Wallis <awallis-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
> ---
>  Documentation/devicetree/bindings/usb/usb-xhci.txt |  1 +
>  drivers/usb/host/xhci-plat.c                       | 15 +++++++++++++++
>  drivers/usb/host/xhci.c                            |  7 ++-----
>  drivers/usb/host/xhci.h                            |  2 ++
>  4 files changed, 20 insertions(+), 5 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/usb/usb-xhci.txt b/Documentation/devicetree/bindings/usb/usb-xhci.txt
> index ae6e484..3998459 100644
> --- a/Documentation/devicetree/bindings/usb/usb-xhci.txt
> +++ b/Documentation/devicetree/bindings/usb/usb-xhci.txt
> @@ -29,6 +29,7 @@ Optional properties:
>    - usb2-lpm-disable: indicate if we don't want to enable USB2 HW LPM
>    - usb3-lpm-capable: determines if platform is USB3 LPM capable
>    - quirk-broken-port-ped: set if the controller has broken port disable mechanism
> +  - imod-interval: IMOD_INTERVAL in nano-seconds. Default is 40000
>  
>  Example:
>  	usb@f0931000 {
> diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
> index 09f164f..f7730c8 100644
> --- a/drivers/usb/host/xhci-plat.c
> +++ b/drivers/usb/host/xhci-plat.c
> @@ -23,6 +23,7 @@
>  #include "xhci-plat.h"
>  #include "xhci-mvebu.h"
>  #include "xhci-rcar.h"
> +#include "xhci-mtk.h"
>  
>  static struct hc_driver __read_mostly xhci_plat_hc_driver;
>  
> @@ -269,6 +270,20 @@ static int xhci_plat_probe(struct platform_device *pdev)
>  	if (device_property_read_bool(&pdev->dev, "quirk-broken-port-ped"))
>  		xhci->quirks |= XHCI_BROKEN_PORT_PED;
>  
> +	/* imod interval in nanoseconds */
> +	if (device_property_read_u32(sysdev,
> +		"imod-interval", &xhci->imod_interval))
> +		xhci->imod_interval = 40000;

So no matter what value you read, you set it to 40000?  Or am I reading
this code incorrectly?

There's a good reason putting function calls inside if() is considered a
bad coding style :)

thanks,

greg k-h
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Re: [PATCH v1] usb: xhci: allow imod-interval to be configurable

[Adam Wallis]

On 11/28/2017 2:35 PM, Greg Kroah-Hartman wrote:
> On Tue, Nov 28, 2017 at 12:11:46PM -0500, Adam Wallis wrote:
>> The xHCI driver currently has the IMOD set to 160, which
>> translates to an IMOD interval of 40,000ns (160 * 250)ns
>>
[..]
>> --- a/drivers/usb/host/xhci-plat.c
>> +++ b/drivers/usb/host/xhci-plat.c
>> @@ -23,6 +23,7 @@
>>  #include "xhci-plat.h"
>>  #include "xhci-mvebu.h"
>>  #include "xhci-rcar.h"
>> +#include "xhci-mtk.h"
>>  
>>  static struct hc_driver __read_mostly xhci_plat_hc_driver;
>>  
>> @@ -269,6 +270,20 @@ static int xhci_plat_probe(struct platform_device *pdev)
>>  	if (device_property_read_bool(&pdev->dev, "quirk-broken-port-ped"))
>>  		xhci->quirks |= XHCI_BROKEN_PORT_PED;
>>  
>> +	/* imod interval in nanoseconds */
>> +	if (device_property_read_u32(sysdev,
>> +		"imod-interval", &xhci->imod_interval))
>> +		xhci->imod_interval = 40000;
> 
> So no matter what value you read, you set it to 40000?  Or am I reading
> this code incorrectly?

I think you may be reading the code incorrectly. device_property_read_u32()
returns 0 when the property is found and valid...and stored into
xhci->imod_interval. When 0 is returned in this case, the default value of
40,000 is skipped over.

If the property is not found, a number of different errors could be returned,
but any of them will cause the default value to be used.

> There's a good reason putting function calls inside if() is considered a
> bad coding style :)

I do not disagree with you, however, I was trying to maintain style consistency
with the device property reads with the xhci_plat_probe function.

If I break that consistency, a couple of ways I might write this cleaner

1) set xhci->imod_interval to 40,000 before the call to
device_property_read_u32. If the property exists in a firmware node, it will
update the imod_interval value...if it does not exist, it will not update this
value and the default will be used. In this case, I would not even check the
return value. This method is used quite a bit in the kernel.

2) use a if (device_property_present()) and check to see if that property is
even present. If so, call device_property_read_u32() without check return value.
This has the downside of still using a function call within the if() which you
have already indicated is not your preference.

3) add a retval and test off of this instead of using the function directly in
the if()

> thanks,
> 
> greg k-h

Thanks for taking time to review my patch. I really have no strong preference on
how call device_property_read_u32() is tested and I am open to any suggestions.
Adam


-- 
Adam Wallis
Qualcomm Datacenter Technologies as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project.
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Re: [PATCH v1] usb: xhci: allow imod-interval to be configurable

[Greg Kroah-Hartman]

On Tue, Nov 28, 2017 at 03:32:29PM -0500, Adam Wallis wrote:
> On 11/28/2017 2:35 PM, Greg Kroah-Hartman wrote:
> > On Tue, Nov 28, 2017 at 12:11:46PM -0500, Adam Wallis wrote:
> >> The xHCI driver currently has the IMOD set to 160, which
> >> translates to an IMOD interval of 40,000ns (160 * 250)ns
> >>
> [..]
> >> --- a/drivers/usb/host/xhci-plat.c
> >> +++ b/drivers/usb/host/xhci-plat.c
> >> @@ -23,6 +23,7 @@
> >>  #include "xhci-plat.h"
> >>  #include "xhci-mvebu.h"
> >>  #include "xhci-rcar.h"
> >> +#include "xhci-mtk.h"
> >>  
> >>  static struct hc_driver __read_mostly xhci_plat_hc_driver;
> >>  
> >> @@ -269,6 +270,20 @@ static int xhci_plat_probe(struct platform_device *pdev)
> >>  	if (device_property_read_bool(&pdev->dev, "quirk-broken-port-ped"))
> >>  		xhci->quirks |= XHCI_BROKEN_PORT_PED;
> >>  
> >> +	/* imod interval in nanoseconds */
> >> +	if (device_property_read_u32(sysdev,
> >> +		"imod-interval", &xhci->imod_interval))
> >> +		xhci->imod_interval = 40000;
> > 
> > So no matter what value you read, you set it to 40000?  Or am I reading
> > this code incorrectly?
> 
> I think you may be reading the code incorrectly. device_property_read_u32()
> returns 0 when the property is found and valid...and stored into
> xhci->imod_interval. When 0 is returned in this case, the default value of
> 40,000 is skipped over.

Yes, it is very hard to read :(

> > There's a good reason putting function calls inside if() is considered a
> > bad coding style :)
> 
> I do not disagree with you, however, I was trying to maintain style consistency
> with the device property reads with the xhci_plat_probe function.

Ok, maybe it should all be fixed :)

> If I break that consistency, a couple of ways I might write this cleaner
> 
> 1) set xhci->imod_interval to 40,000 before the call to
> device_property_read_u32. If the property exists in a firmware node, it will
> update the imod_interval value...if it does not exist, it will not update this
> value and the default will be used. In this case, I would not even check the
> return value. This method is used quite a bit in the kernel.

Sounds like a reasonable way to do it.

thanks,

greg k-h
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Re: [PATCH v1] usb: xhci: allow imod-interval to be configurable

[Rob Herring]

On Wed, Nov 29, 2017 at 09:09:41AM +0100, Greg Kroah-Hartman wrote:
> On Tue, Nov 28, 2017 at 03:32:29PM -0500, Adam Wallis wrote:
> > On 11/28/2017 2:35 PM, Greg Kroah-Hartman wrote:
> > > On Tue, Nov 28, 2017 at 12:11:46PM -0500, Adam Wallis wrote:
> > >> The xHCI driver currently has the IMOD set to 160, which
> > >> translates to an IMOD interval of 40,000ns (160 * 250)ns
> > >>
> > [..]
> > >> --- a/drivers/usb/host/xhci-plat.c
> > >> +++ b/drivers/usb/host/xhci-plat.c
> > >> @@ -23,6 +23,7 @@
> > >>  #include "xhci-plat.h"
> > >>  #include "xhci-mvebu.h"
> > >>  #include "xhci-rcar.h"
> > >> +#include "xhci-mtk.h"
> > >>  
> > >>  static struct hc_driver __read_mostly xhci_plat_hc_driver;
> > >>  
> > >> @@ -269,6 +270,20 @@ static int xhci_plat_probe(struct platform_device *pdev)
> > >>  	if (device_property_read_bool(&pdev->dev, "quirk-broken-port-ped"))
> > >>  		xhci->quirks |= XHCI_BROKEN_PORT_PED;
> > >>  
> > >> +	/* imod interval in nanoseconds */
> > >> +	if (device_property_read_u32(sysdev,
> > >> +		"imod-interval", &xhci->imod_interval))
> > >> +		xhci->imod_interval = 40000;
> > > 
> > > So no matter what value you read, you set it to 40000?  Or am I reading
> > > this code incorrectly?
> > 
> > I think you may be reading the code incorrectly. device_property_read_u32()
> > returns 0 when the property is found and valid...and stored into
> > xhci->imod_interval. When 0 is returned in this case, the default value of
> > 40,000 is skipped over.
> 
> Yes, it is very hard to read :(
> 
> > > There's a good reason putting function calls inside if() is considered a
> > > bad coding style :)
> > 
> > I do not disagree with you, however, I was trying to maintain style consistency
> > with the device property reads with the xhci_plat_probe function.
> 
> Ok, maybe it should all be fixed :)
> 
> > If I break that consistency, a couple of ways I might write this cleaner
> > 
> > 1) set xhci->imod_interval to 40,000 before the call to
> > device_property_read_u32. If the property exists in a firmware node, it will
> > update the imod_interval value...if it does not exist, it will not update this
> > value and the default will be used. In this case, I would not even check the
> > return value. This method is used quite a bit in the kernel.
> 
> Sounds like a reasonable way to do it.

And is exactly how the (of|device)_property_read_* functions were 
intended to be used.

Rob
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Re: [PATCH v1] usb: xhci: allow imod-interval to be configurable

[Rob Herring]

On Tue, Nov 28, 2017 at 12:11:46PM -0500, Adam Wallis wrote:
> The xHCI driver currently has the IMOD set to 160, which
> translates to an IMOD interval of 40,000ns (160 * 250)ns
> 
> Commit 0cbd4b34cda9 ("xhci: mediatek: support MTK xHCI host controller")
> introduced a QUIRK for the MTK platform to adjust this interval to 20,
> which translates to an IMOD interval of 5,000ns (20 * 250)ns. This is
> due to the fact that the MTK controller IMOD interval is 8 times
> as much as defined in xHCI spec.
> 
> Instead of adding more quirk bits for additional platforms, this patch
> introduces the ability for vendors to set the IMOD_INTERVAL as is
> optimal for their platform. By using device_property_read_u32() on
> "imod-interval", the IMOD INTERVAL can be specified in nano seconds. If
> no interval is specified, the default of 40,000ns (IMOD=160) will be
> used.
> 
> No bounds checking has been implemented due to the fact that a vendor
> may have violated the spec and would need to specify a value outside of
> the max 8,000 IRQs/second limit specified in the xHCI spec.
> 
> Backwards compatibility is maintained for MTK_HOSTS through the quirk
> bit, however, imod_interval should be pushed into device tree at a
> future point and this quirk should be removed from xhci_plat_probe
> 
> Signed-off-by: Adam Wallis <awallis-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
> ---
>  Documentation/devicetree/bindings/usb/usb-xhci.txt |  1 +
>  drivers/usb/host/xhci-plat.c                       | 15 +++++++++++++++
>  drivers/usb/host/xhci.c                            |  7 ++-----
>  drivers/usb/host/xhci.h                            |  2 ++
>  4 files changed, 20 insertions(+), 5 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/usb/usb-xhci.txt b/Documentation/devicetree/bindings/usb/usb-xhci.txt
> index ae6e484..3998459 100644
> --- a/Documentation/devicetree/bindings/usb/usb-xhci.txt
> +++ b/Documentation/devicetree/bindings/usb/usb-xhci.txt
> @@ -29,6 +29,7 @@ Optional properties:
>    - usb2-lpm-disable: indicate if we don't want to enable USB2 HW LPM
>    - usb3-lpm-capable: determines if platform is USB3 LPM capable
>    - quirk-broken-port-ped: set if the controller has broken port disable mechanism
> +  - imod-interval: IMOD_INTERVAL in nano-seconds. Default is 40000

Needs a unit suffix as defined in property-units.txt.

Rob
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