IronPort-SDR: 3chzwyy+iI6ZKd38+sRzUMtIyG7x8FnYgdxB7SYQeG00y7qMbfwHcseAqr6xwfz1L4Ucy8mkQN
 LlFxCbtnIdTA==
IronPort-SDR: qHszbkCVUCJs+8BhGHXO+Pv95oy+gknGAlPcRHinJQ9dZtft5IVBu22ohtmSktDiYxXe2Wrt2d
 mmNNOo2TdFgg==
Subject: Re: [PATCH v2 4/7] usb: xhci: Workaround undercalculated BW for
 fullspeed BI
To:     Thinh Nguyen <Thinh.Nguyen@synopsys.com>,
        Felipe Balbi <balbi@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-usb@vger.kernel.org, Mathias Nyman <mathias.nyman@intel.com>
Cc:     John Youn <John.Youn@synopsys.com>
References: <cover.1618014279.git.Thinh.Nguyen@synopsys.com>
 <ed5ddb78abd157ef2bb9317545b9fec63c6a5b66.1618014279.git.Thinh.Nguyen@synopsys.com>
From:   Mathias Nyman <mathias.nyman@linux.intel.com>
Autocrypt: addr=mathias.nyman@linux.intel.com; prefer-encrypt=mutual; keydata=
 mQINBFMB0ccBEADd+nZnZrFDsIjQtclVz6OsqFOQ6k0nQdveiDNeBuwyFYykkBpaGekoHZ6f
 lH4ogPZzQ+pzoJEMlRGXc881BIggKMCMH86fYJGfZKWdfpg9O6mqSxyEuvBHKe9eZCBKPvoC
 L2iwygtO8TcXXSCynvXSeZrOwqAlwnxWNRm4J2ikDck5S5R+Qie0ZLJIfaId1hELofWfuhy+
 tOK0plFR0HgVVp8O7zWYT2ewNcgAzQrRbzidA3LNRfkL7jrzyAxDapuejuK8TMrFQT/wW53e
 uegnXcRJaibJD84RUJt+mJrn5BvZ0MYfyDSc1yHVO+aZcpNr+71yZBQVgVEI/AuEQ0+p9wpt
 O9Wt4zO2KT/R5lq2lSz1MYMJrtfFRKkqC6PsDSB4lGSgl91XbibK5poxrIouVO2g9Jabg04T
 MIPpVUlPme3mkYHLZUsboemRQp5/pxV4HTFR0xNBCmsidBICHOYAepCzNmfLhfo1EW2Uf+t4
 L8IowAaoURKdgcR2ydUXjhACVEA/Ldtp3ftF4hTQ46Qhba/p4MUFtDAQ5yeA5vQVuspiwsqB
 BoL/298+V119JzM998d70Z1clqTc8fiGMXyVnFv92QKShDKyXpiisQn2rrJVWeXEIVoldh6+
 J8M3vTwzetnvIKpoQdSFJ2qxOdQ8iYRtz36WYl7hhT3/hwkHuQARAQABtCdNYXRoaWFzIE55
 bWFuIDxtYXRoaWFzLm55bWFuQGdtYWlsLmNvbT6JAjsEEwECACUCGwMGCwkIBwMCBhUIAgkK
 CwQWAgMBAh4BAheABQJTAeo1AhkBAAoJEFiDn/uYk8VJOdIP/jhA+RpIZ7rdUHFIYkHEKzHw
 tkwrJczGA5TyLgQaI8YTCTPSvdNHU9Rj19mkjhUO/9MKvwfoT2RFYqhkrtk0K92STDaBNXTL
 JIi4IHBqjXOyJ/dPADU0xiRVtCHWkBgjEgR7Wihr7McSdVpgupsaXhbZjXXgtR/N7PE0Wltz
 hAL2GAnMuIeJyXhIdIMLb+uyoydPCzKdH6znfu6Ox76XfGWBCqLBbvqPXvk4oH03jcdt+8UG
 2nfSeti/To9ANRZIlSKGjddCGMa3xzjtTx9ryf1Xr0MnY5PeyNLexpgHp93sc1BKxKKtYaT0
 lR6p0QEKeaZ70623oB7Sa2Ts4IytqUVxkQKRkJVWeQiPJ/dZYTK5uo15GaVwufuF8VTwnMkC
 4l5X+NUYNAH1U1bpRtlT40aoLEUhWKAyVdowxW4yGCP3nL5E69tZQQgsag+OnxBa6f88j63u
 wxmOJGNXcwCerkCb+wUPwJzChSifFYmuV5l89LKHgSbv0WHSN9OLkuhJO+I9fsCNvro1Y7dT
 U/yq4aSVzjaqPT3yrnQkzVDxrYT54FLWO1ssFKAOlcfeWzqrT9QNcHIzHMQYf5c03Kyq3yMI
 Xi91hkw2uc/GuA2CZ8dUD3BZhUT1dm0igE9NViE1M7F5lHQONEr7MOCg1hcrkngY62V6vh0f
 RcDeV0ISwlZWuQINBFMB0ccBEACXKmWvojkaG+kh/yipMmqZTrCozsLeGitxJzo5hq9ev31N
 2XpPGx4AGhpccbco63SygpVN2bOd0W62fJJoxGohtf/g0uVtRSuK43OTstoBPqyY/35+VnAV
 oA5cnfvtdx5kQPIL6LRcxmYKgN4/3+A7ejIxbOrjWFmbWCC+SgX6mzHHBrV0OMki8R+NnrNa
 NkUmMmosi7jBSKdoi9VqDqgQTJF/GftvmaZHqgmVJDWNrCv7UiorhesfIWPt1O/AIk9luxlE
 dHwkx5zkWa9CGYvV6LfP9BznendEoO3qYZ9IcUlW727Le80Q1oh69QnHoI8pODDBBTJvEq1h
 bOWcPm/DsNmDD8Rwr/msRmRyIoxjasFi5WkM/K/pzujICKeUcNGNsDsEDJC5TCmRO/TlvCvm
 0X+vdfEJRZV6Z+QFBflK1asUz9QHFre5csG8MyVZkwTR9yUiKi3KiqQdaEu+LuDD2CGF5t68
 xEl66Y6mwfyiISkkm3ETA4E8rVZP1rZQBBm83c5kJEDvs0A4zrhKIPTcI1smK+TWbyVyrZ/a
 mGYDrZzpF2N8DfuNSqOQkLHIOL3vuOyx3HPzS05lY3p+IIVmnPOEdZhMsNDIGmVorFyRWa4K
 uYjBP/W3E5p9e6TvDSDzqhLoY1RHfAIadM3I8kEx5wqco67VIgbIHHB9DbRcxQARAQABiQIf
 BBgBAgAJBQJTAdHHAhsMAAoJEFiDn/uYk8VJb7AQAK56tgX8V1Wa6RmZDmZ8dmBC7W8nsMRz
 PcKWiDSMIvTJT5bygMy1lf7gbHXm7fqezRtSfXAXr/OJqSA8LB2LWfThLyuuCvrdNsQNrI+3
 D+hjHJjhW/4185y3EdmwwHcelixPg0X9EF+lHCltV/w29Pv3PiGDkoKxJrnOpnU6jrwiBebz
 eAYBfpSEvrCm4CR4hf+T6MdCs64UzZnNt0nxL8mLCCAGmq1iks9M4bZk+LG36QjCKGh8PDXz
 9OsnJmCggptClgjTa7pO6040OW76pcVrP2rZrkjo/Ld/gvSc7yMO/m9sIYxLIsR2NDxMNpmE
 q/H7WO+2bRG0vMmsndxpEYS4WnuhKutoTA/goBEhtHu1fg5KC+WYXp9wZyTfeNPrL0L8F3N1
 BCEYefp2JSZ/a355X6r2ROGSRgIIeYjAiSMgGAZMPEVsdvKsYw6BH17hDRzltNyIj5S0dIhb
 Gjynb3sXforM/GVbr4mnuxTdLXQYlj2EJ4O4f0tkLlADT7podzKSlSuZsLi2D+ohKxtP3U/r
 42i8PBnX2oAV0UIkYk7Oel/3hr0+BP666SnTls9RJuoXc7R5XQVsomqXID6GmjwFQR5Wh/RE
 IJtkiDAsk37cfZ9d1kZ2gCQryTV9lmflSOB6AFZkOLuEVSC5qW8M/s6IGDfYXN12YJaZPptJ fiD/
Message-ID: <76ecefd7-d294-485a-1e2b-e5e556e2a3f7@linux.intel.com>
Date:   Wed, 28 Apr 2021 14:57:14 +0300
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.10.0
MIME-Version: 1.0
In-Reply-To: <ed5ddb78abd157ef2bb9317545b9fec63c6a5b66.1618014279.git.Thinh.Nguyen@synopsys.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Precedence: bulk

On 10.4.2021 3.47, Thinh Nguyen wrote:
> DWC_usb31 host version 1.90a and prior undercalculates the bandwidth
> available for interrupt endpoints. The controller will return bandwidth
> error on config endpoint commands if there are already 6 or more
> fullspeed interrupt endpoints with bInterval of 4 (or 4ms) associated
> with a single fullspeed bus instance (BI).
> 
> To workaround this, configure and use the endpoint at a shorter
> interrupt interval. Lower the ep_ctx interval from 5 to 4 (or 2ms)
> for interrupt endpoints of the fullspeed BI. Note: we have not observed
> functional impact to the fullspeed devices by lowering the interrupt
> service interval (at least for a few devices that we tested).
> 
> To simplify the workaround, let's just check and apply the workaround if
> the endpoint is a fullspeed interrupt endpoint with interval of 4ms and
> if the top parent device is also operating in fullspeed (i.e. associated
> with fullspeed BI).
> 
> Signed-off-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
> ---
> Changes in v2:
> - None
> 
> Note:
> Checkpatch will give a warning below for getting top_dev:
> 	WARNING: suspect code indent for conditional statements
> 
> Since this logic is done everywhere else in the driver, I'm keeping it
> consistent here.
> 
>  drivers/usb/host/xhci-mem.c     | 23 +++++++++++++++++++++++
>  include/linux/usb/xhci-quirks.h |  1 +
>  2 files changed, 24 insertions(+)
> 
> diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
> index 1053b43008e4..e01d0ddb012a 100644
> --- a/drivers/usb/host/xhci-mem.c
> +++ b/drivers/usb/host/xhci-mem.c
> @@ -1463,6 +1463,29 @@ int xhci_endpoint_init(struct xhci_hcd *xhci,
>  		}
>  	}
>  
> +	/*
> +	 * Check for undercalculated bandwidth quirk for interrupt endpoints
> +	 * associated with fullspeed BI.
> +	 */
> +	if ((xhci->quirks & XHCI_LIMIT_FS_BI_INTR_EP) &&
> +	    usb_endpoint_xfer_int(&ep->desc) &&
> +	    udev->speed == USB_SPEED_FULL &&
> +	    interval == 5) {
> +		struct usb_device *top_dev;
> +
> +		for (top_dev = udev;
> +		     top_dev->parent && top_dev->parent->parent;
> +		     top_dev = top_dev->parent)
> +			/* Found device below root hub */;
> +
> +		/*
> +		 * If the top device is operating at fullspeed, then the
> +		 * controller is using fullspeed BI for this device.
> +		 */
> +		if (top_dev->speed == USB_SPEED_FULL)
> +			interval = 4;
> +	}
> +


If we write a new xhci-snps driver then adjusting the interval could be done in the
.add_endpoint override, after calling xhci_add_endpoint()

If not then something like this should work.
Maybe turn it into a separate function for readability.

xhci_tune_interval_quirk(xhci, udev, ep, &interval)

-Mathias