From: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
To: Prashanth K <quic_prashk@quicinc.com>
Cc: Thinh Nguyen <Thinh.Nguyen@synopsys.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Wesley Cheng <quic_wcheng@quicinc.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>
Subject: Re: [RFC PATCH] usb: dwc3: Poll CMDACT after issuing EndXfer command
Date: Wed, 24 Apr 2024 01:33:45 +0000 [thread overview]
Message-ID: <20240424013342.5itkoewx7jdonyk4@synopsys.com> (raw)
In-Reply-To: <20240422090539.3986723-1-quic_prashk@quicinc.com>
On Mon, Apr 22, 2024, Prashanth K wrote:
> Currently DWC3 controller revisions 3.10a and later supports
DWC3 -> DWC_usb3 to highlight not being DWC_usb31 and DWC_usb32.
> GUCTL[14: Rst_actbitlater] bit which allows polling CMDACT bit
GUCTL -> GUCTL2
> to know whether ENDXFER command is completed. Other revisions
> wait 1ms for ENDXFER completion after issuing the command.
>
> Consider a case where an IN request was queued, and parallelly
> soft_disconnect was called (due to ffs_epfile_release). This
> eventually calls stop_active_transfer with IOC cleared, hence
> send_gadget_ep_cmd() skips waiting for CMDACT cleared during
> endxfer. For DWC3 controllers with revisions >= 310a, we don't
> forcefully wait for 1ms either, and we proceed by unmapping the
> requests. If ENDXFER didn't complete by this time, it leads to
> SMMU faults since the controller would still be accessing those
> requests.
>
> DWC3 databook specifies that CMDACT bit can be polled to check
> completion of the EndXfer. Hence use it in stop_active_transfer
> to know whether the ENDXFER got completed.
>
> Section 3.2.2.7 Command 8: End Transfer (DEPENDXFER)
> Note: If GUCTL2[Rst_actbitlater] is set, Software can poll the
> completion of the End Transfer command by polling the command
> active bit to be cleared to 0.
>
> Fixes: b353eb6dc285 ("usb: dwc3: gadget: Skip waiting for CMDACT cleared during endxfer")
> Signed-off-by: Prashanth K <quic_prashk@quicinc.com>
> ---
> drivers/usb/dwc3/gadget.c | 22 ++++++++++++++++++++--
> 1 file changed, 20 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 4df2661f6675..acb54c48451f 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -1701,8 +1701,8 @@ static int __dwc3_stop_active_transfer(struct dwc3_ep *dep, bool force, bool int
> {
> struct dwc3 *dwc = dep->dwc;
> struct dwc3_gadget_ep_cmd_params params;
> - u32 cmd;
> - int ret;
> + u32 cmd, reg;
> + int ret, retries = 500;
Please separate variable declarations per line.
>
> cmd = DWC3_DEPCMD_ENDTRANSFER;
> cmd |= force ? DWC3_DEPCMD_HIPRI_FORCERM : 0;
> @@ -1726,6 +1726,24 @@ static int __dwc3_stop_active_transfer(struct dwc3_ep *dep, bool force, bool int
> if (!interrupt) {
> if (!DWC3_IP_IS(DWC3) || DWC3_VER_IS_PRIOR(DWC3, 310A))
> mdelay(1);
> + else {
> + /*
> + * ENDXFER polling is available on version 3.10a and later of
Try to note the IP along with version (eg. DWC_usb3 v3.10a).
> + * the DWC3 controller (This is enabled by setting GUCTL2[14])
Did we check to know that we set GUCTL2.Rst_actbitlater to start
polling for CMDACT?
> + */
> + do {
> + reg = dwc3_readl(dep->regs, DWC3_DEPCMD);
> + if (!(reg & DWC3_DEPCMD_CMDACT))
> + break;
> + udelay(2);
udelay of 2 is really small. Try at least 200us.
> + } while (--retries);
> +
> + if (!retries && (dwc->ep0state != EP0_SETUP_PHASE)) {
> + dep->flags |= DWC3_EP_DELAY_STOP;
> + return -ETIMEDOUT;
> + }
> + }
> +
> dep->flags &= ~DWC3_EP_TRANSFER_STARTED;
> } else if (!ret) {
> dep->flags |= DWC3_EP_END_TRANSFER_PENDING;
> --
> 2.25.1
>
Did you observe issues with DWC_usb31? How much longer did your setup
need to complete End Transfer command?
I would prefer a solution that applies for all IPs. Do you observe any
impact should we increase the mdelay()? I don't expect much impact since
this should only happen during endpoint disbling, which is not a common
operation.
Thanks,
Thinh
next prev parent reply other threads:[~2024-04-24 1:33 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-22 9:05 [RFC PATCH] usb: dwc3: Poll CMDACT after issuing EndXfer command Prashanth K
2024-04-24 1:33 ` Thinh Nguyen [this message]
2024-04-24 8:44 ` Prashanth K
2024-04-24 22:36 ` Thinh Nguyen
2024-04-25 3:55 ` Prashanth K
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