Re: [RESEND PATCH v2 2/2] usb: dwc3: gadget: Properly set maxpacket limit

[Felipe Balbi <balbi@kernel.org>]

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Thinh Nguyen <Thinh.Nguyen@synopsys.com> writes:

> Hi,
>
> Thinh Nguyen wrote:
>> Currently the calculation of max packet size limit for IN endpoints is
>> too restrictive. This prevents a matching of a capable hardware endpoint
>> during configuration. Below is the minimum recommended HW configuration
>> to support a particular endpoint setup from the databook:
>>
>> For OUT endpoints, the databook recommended the minimum RxFIFO size to
>> be at least 3x MaxPacketSize + 3x setup packets size (8 bytes each) +
>> clock crossing margin (16 bytes).
>>
>> For IN endpoints, the databook recommended the minimum TxFIFO size to be
>> at least 3x MaxPacketSize for endpoints that support burst. If the
>> endpoint doesn't support burst or when the device is operating in USB
>> 2.0 mode, a minimum TxFIFO size of 2x MaxPacketSize is recommended.
>>
>> Base on these recommendations, we can calculate the MaxPacketSize limit
>> of each endpoint. This patch revises the IN endpoint MaxPacketSize limit
>> and also sets the MaxPacketSize limit for OUT endpoints.
>>
>> Reference: Databook 3.30a section 3.2.2 and 3.2.3
>>
>> Signed-off-by: Thinh Nguyen <thinhn@synopsys.com>
>> ---
>> Changes in v2 -
>>    None
>>
>>   drivers/usb/dwc3/core.h   |  4 ++++
>>   drivers/usb/dwc3/gadget.c | 52 +++++++++++++++++++++++++++++++++++++----------
>>   2 files changed, 45 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
>> index 6a6baadcb697..0f019db5e125 100644
>> --- a/drivers/usb/dwc3/core.h
>> +++ b/drivers/usb/dwc3/core.h
>> @@ -309,6 +309,10 @@
>>   #define DWC3_GTXFIFOSIZ_TXFDEP(n)	((n) & 0xffff)
>>   #define DWC3_GTXFIFOSIZ_TXFSTADDR(n)	((n) & 0xffff0000)
>>   
>> +/* Global RX Fifo Size Register */
>> +#define DWC31_GRXFIFOSIZ_RXFDEP(n)	((n) & 0x7fff)	/* DWC_usb31 only */
>> +#define DWC3_GRXFIFOSIZ_RXFDEP(n)	((n) & 0xffff)
>> +
>>   /* Global Event Size Registers */
>>   #define DWC3_GEVNTSIZ_INTMASK		BIT(31)
>>   #define DWC3_GEVNTSIZ_SIZE(n)		((n) & 0xffff)
>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>> index 5da266173146..3b3e6a655c6a 100644
>> --- a/drivers/usb/dwc3/gadget.c
>> +++ b/drivers/usb/dwc3/gadget.c
>> @@ -2207,7 +2207,6 @@ static int dwc3_gadget_init_in_endpoint(struct dwc3_ep *dep)
>>   {
>>   	struct dwc3 *dwc = dep->dwc;
>>   	int mdwidth;
>> -	int kbytes;
>>   	int size;
>>   
>>   	mdwidth = DWC3_MDWIDTH(dwc->hwparams.hwparams0);
>> @@ -2223,17 +2222,17 @@ static int dwc3_gadget_init_in_endpoint(struct dwc3_ep *dep)
>>   	/* FIFO Depth is in MDWDITH bytes. Multiply */
>>   	size *= mdwidth;
>>   
>> -	kbytes = size / 1024;
>> -	if (kbytes == 0)
>> -		kbytes = 1;
>> -
>>   	/*
>> -	 * FIFO sizes account an extra MDWIDTH * (kbytes + 1) bytes for
>> -	 * internal overhead. We don't really know how these are used,
>> -	 * but documentation say it exists.
>> +	 * To meet performance requirement, a minimum TxFIFO size of 3x
>> +	 * MaxPacketSize is recommended for endpoints that support burst and a
>> +	 * minimum TxFIFO size of 2x MaxPacketSize for endpoints that don't
>> +	 * support burst. Use those numbers and we can calculate the max packet
>> +	 * limit as below.
>>   	 */
>> -	size -= mdwidth * (kbytes + 1);
>> -	size /= kbytes;
>> +	if (dwc->maximum_speed >= USB_SPEED_SUPER)
>> +		size /= 3;
>> +	else
>> +		size /= 2;
>>   
>>   	usb_ep_set_maxpacket_limit(&dep->endpoint, size);
>>   
>> @@ -2251,8 +2250,39 @@ static int dwc3_gadget_init_in_endpoint(struct dwc3_ep *dep)
>>   static int dwc3_gadget_init_out_endpoint(struct dwc3_ep *dep)
>>   {
>>   	struct dwc3 *dwc = dep->dwc;
>> +	int mdwidth;
>> +	int size;
>> +
>> +	mdwidth = DWC3_MDWIDTH(dwc->hwparams.hwparams0);
>> +
>> +	/* MDWIDTH is represented in bits, convert to bytes */
>> +	mdwidth /= 8;
>>   
>> -	usb_ep_set_maxpacket_limit(&dep->endpoint, 1024);
>> +	/* All OUT endpoints share a single RxFIFO space */
>> +	size = dwc3_readl(dwc->regs, DWC3_GRXFIFOSIZ(0));
>> +	if (dwc3_is_usb31(dwc))
>> +		size = DWC31_GRXFIFOSIZ_RXFDEP(size);
>> +	else
>> +		size = DWC3_GRXFIFOSIZ_RXFDEP(size);
>> +
>> +	/* FIFO depth is in MDWDITH bytes */
>> +	size *= mdwidth;
>> +
>> +	/*
>> +	 * To meet performance requirement, a minimum recommended RxFIFO size
>> +	 * is defined as follow:
>> +	 * RxFIFO size >= (3 x MaxPacketSize) +
>> +	 * (3 x 8 bytes setup packets size) + (16 bytes clock crossing margin)
>> +	 *
>> +	 * Then calculate the max packet limit as below.
>> +	 */
>> +	size -= (3 * 8) + 16;
>> +	if (size < 0)
>> +		size = 0;
>> +	else
>> +		size /= 3;
>> +
>> +	usb_ep_set_maxpacket_limit(&dep->endpoint, size);
>>   	dep->endpoint.max_streams = 15;
>>   	dep->endpoint.ops = &dwc3_gadget_ep_ops;
>>   	list_add_tail(&dep->endpoint.ep_list,
>
> Please let me know if these patches are not clear or that they are lost 
> somewhere. I'll try my best to clarify if anything's not clear.

They're now in my testing/fixes. Thanks

-- 
balbi

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