linux-kernel - Re: [PATCH] usb: chipidea: udc: make controller hardware endpoint primed

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Message-ID: <20210912074105.GA4808@Peter>
Date:   Sun, 12 Sep 2021 15:41:05 +0800
From:   Peter Chen <peter.chen@...nel.org>
To:     Piyush Mehta <piyush.mehta@...inx.com>
Cc:     gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, git@...inx.com, sgoud@...inx.com,
        michal.simek@...inx.com
Subject: Re: [PATCH] usb: chipidea: udc: make controller hardware endpoint
 primed

On 21-09-08 14:13:21, Piyush Mehta wrote:
> Root-cause:
> There is an issue like endpoint is not recognized as primed, when bus
> have more pressure and the add dTD tripwire semaphore (ATDTW bit in
> USBCMD register) that can cause the controller to ignore a dTD that is
> added to a primed endpoint.
> This issue observed with the Windows10 host machine.
> 
> Workaround:
> The software must implement a periodic cycle, and check for each dTD,
> if the endpoint is primed. It can do this by reading the corresponding
> bits in the ENDPTPRIME and ENDPTSTAT registers. If these bits are read
> at 0, the software needs to re-prime the endpoint by writing 1 to the
> corresponding bit in the ENDPTPRIME register.
> 
> Signed-off-by: Piyush Mehta <piyush.mehta@...inx.com>
> ---
>  drivers/usb/chipidea/udc.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/usb/chipidea/udc.c b/drivers/usb/chipidea/udc.c
> index 8834ca6..d970f45 100644
> --- a/drivers/usb/chipidea/udc.c
> +++ b/drivers/usb/chipidea/udc.c
> @@ -49,6 +49,8 @@ ctrl_endpt_in_desc = {
>  	.wMaxPacketSize  = cpu_to_le16(CTRL_PAYLOAD_MAX),
>  };
>  
> +static int reprime_dtd(struct ci_hdrc *ci, struct ci_hw_ep *hwep,
> +		       struct td_node *node);
>  /**
>   * hw_ep_bit: calculates the bit number
>   * @num: endpoint number
> @@ -599,8 +601,15 @@ static int _hardware_enqueue(struct ci_hw_ep *hwep, struct ci_hw_req *hwreq)
>  
>  		prevlastnode->ptr->next = cpu_to_le32(next);
>  		wmb();
> +
> +		if (ci->rev == CI_REVISION_22) {
> +			if (!hw_read(ci, OP_ENDPTSTAT, BIT(n)))
> +				reprime_dtd(ci, hwep, prevlastnode);
> +		}
> +

Only for version 2.2?

>  		if (hw_read(ci, OP_ENDPTPRIME, BIT(n)))
>  			goto done;
> +

No blank line.

>  		do {
>  			hw_write(ci, OP_USBCMD, USBCMD_ATDTW, USBCMD_ATDTW);
>  			tmp_stat = hw_read(ci, OP_ENDPTSTAT, BIT(n));
> -- 
> 2.7.4
> 

-- 

Thanks,
Peter Chen