From e6bdfe36e52f0e552b50acf49a82851eeb122fde Mon Sep 17 00:00:00 2001 From: Catalin Marinas Date: Mon, 23 Mar 2009 12:38:16 +0000 Subject: [PATCH] USB: isp1760: Add a delay before reading the SKIPMAP registers in isp1760-hcd.c The data read from the SKIPMAP registers is not immediately available after writing and the driver panics when a packet is enqueued from the interrupt handler. This patch adds an ndelay(195) before these registers are read (delay value mentioned in section 15.1.1.3 of the ISP1760 data sheet). Signed-off-by: Catalin Marinas Acked-by: Sebastian Andrzej Siewior Signed-off-by: Greg Kroah-Hartman --- drivers/usb/host/isp1760-hcd.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/drivers/usb/host/isp1760-hcd.c b/drivers/usb/host/isp1760-hcd.c index 3172c0fd2a6d..cd07ea3f0c63 100644 --- a/drivers/usb/host/isp1760-hcd.c +++ b/drivers/usb/host/isp1760-hcd.c @@ -819,6 +819,13 @@ static void enqueue_an_ATL_packet(struct usb_hcd *hcd, struct isp1760_qh *qh, u32 atl_regs, payload; u32 buffstatus; + /* + * When this function is called from the interrupt handler to enqueue + * a follow-up packet, the SKIP register gets written and read back + * almost immediately. With ISP1761, this register requires a delay of + * 195ns between a write and subsequent read (see section 15.1.1.3). + */ + ndelay(195); skip_map = isp1760_readl(hcd->regs + HC_ATL_PTD_SKIPMAP_REG); BUG_ON(!skip_map); @@ -853,6 +860,13 @@ static void enqueue_an_INT_packet(struct usb_hcd *hcd, struct isp1760_qh *qh, u32 int_regs, payload; u32 buffstatus; + /* + * When this function is called from the interrupt handler to enqueue + * a follow-up packet, the SKIP register gets written and read back + * almost immediately. With ISP1761, this register requires a delay of + * 195ns between a write and subsequent read (see section 15.1.1.3). + */ + ndelay(195); skip_map = isp1760_readl(hcd->regs + HC_INT_PTD_SKIPMAP_REG); BUG_ON(!skip_map);