Re: [PATCH] [RFC] usb: xhci: Add to check CRR bit in xhci_suspend()

[Mathias Nyman <mathias.nyman@linux.intel.com>]

On 27.04.2015 11:55, Yoshihiro Shimoda wrote:
Hi

> According to the xHCI spec "4.23.2 xHCI Power Management", the CRR bit
> of CRCR register should be zero before setting Run/Stop (R/S) = '0'.
> Otherwise, the STS_HALT is not set until the CRR is cleared on specific
> xHCI controllers. In case of R-Car SoCs, it spent about 90 ms to clear
> the CRR. So, to avoid the quirks XHCI_SLOW_SUSPEND, the driver calls
> the aborting function if the CRR is set to 1.
> 
> Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
> ---
>  drivers/usb/host/xhci-ring.c |  2 +-
>  drivers/usb/host/xhci.c      | 21 ++++++++++++++++++++-
>  drivers/usb/host/xhci.h      |  1 +
>  3 files changed, 22 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
> index f5397a5..21f3932 100644
> --- a/drivers/usb/host/xhci-ring.c
> +++ b/drivers/usb/host/xhci-ring.c
> @@ -280,7 +280,7 @@ void xhci_ring_cmd_db(struct xhci_hcd *xhci)
>  	readl(&xhci->dba->doorbell[0]);
>  }
>  
> -static int xhci_abort_cmd_ring(struct xhci_hcd *xhci)
> +int xhci_abort_cmd_ring(struct xhci_hcd *xhci)
>  {
>  	u64 temp_64;
>  	int ret;
> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> index ec8ac16..d2d81a0 100644
> --- a/drivers/usb/host/xhci.c
> +++ b/drivers/usb/host/xhci.c
> @@ -892,7 +892,7 @@ static void xhci_disable_port_wake_on_bits(struct xhci_hcd *xhci)
>   */
>  int xhci_suspend(struct xhci_hcd *xhci, bool do_wakeup)
>  {
> -	int			rc = 0;
> +	int			rc = 0, ret;
>  	unsigned int		delay = XHCI_MAX_HALT_USEC;
>  	struct usb_hcd		*hcd = xhci_to_hcd(xhci);
>  	u32			command;
> @@ -918,6 +918,25 @@ int xhci_suspend(struct xhci_hcd *xhci, bool do_wakeup)
>  	/* step 1: stop endpoint */
>  	/* skipped assuming that port suspend has done */
>  
> +	/*
> +	 * According to the xHCI spec "4.23.2 xHCI Power Management", the CRR
> +	 * bit of CRCR register should be zero before setting Run/Stop (R/S) > +	 * '0', the driver calls the aborting function if the CRR is set to 1.
> +	 */
> +	if (xhci_read_64(xhci, &xhci->op_regs->cmd_ring) & CMD_RING_RUNNING) {
> +		/* unlock here because this may wait about 5 seconds */
> +		spin_unlock_irq(&xhci->lock);
> +		ret = xhci_abort_cmd_ring(xhci);

Would it work for R-Car if we instead of unlocking and and aborting the command just wait for
the CRR bit to turn 0 before setting Run/stop = 0? 

Aborting the command ring by setting CA bit in CRCR will generate a command abort/stop completion event,
which will point to the stopped/aborted event on the command ring. We are however clearing the command
ring completely in xhci_suspend() right after this, and setting the dequeue pointer to the beginning of
the ring. This will likely mess with the handling of the abort/stop event.   

Waiting for the CRR to clear could be done using: 
xhci_handshake(&xhci->op_regs->cmd_ring, CMD_RING_RUNNING, timeout)

-Mathias