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path: root/drivers/usb/storage/protocol.h
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/*
 * Driver for USB Mass Storage compliant devices
 * Protocol Functions Header File
 *
 * Current development and maintenance by:
 *   (c) 1999, 2000 Matthew Dharm (mdharm-usb@one-eyed-alien.net)
 *
 * This driver is based on the 'USB Mass Storage Class' document. This
 * describes in detail the protocol used to communicate with such
 * devices.  Clearly, the designers had SCSI and ATAPI commands in
 * mind when they created this document.  The commands are all very
 * similar to commands in the SCSI-II and ATAPI specifications.
 *
 * It is important to note that in a number of cases this class
 * exhibits class-specific exemptions from the USB specification.
 * Notably the usage of NAK, STALL and ACK differs from the norm, in
 * that they are used to communicate wait, failed and OK on commands.
 *
 * Also, for certain devices, the interrupt endpoint is used to convey
 * status of a command.
 *
 * Please see http://www.one-eyed-alien.net/~mdharm/linux-usb for more
 * information about this driver.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2, or (at your option) any
 * later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#ifndef _PROTOCOL_H_
#define _PROTOCOL_H_

/* Protocol handling routines */
extern void usb_stor_pad12_command(struct scsi_cmnd*, struct us_data*);
extern void usb_stor_ufi_command(struct scsi_cmnd*, struct us_data*);
extern void usb_stor_transparent_scsi_command(struct scsi_cmnd*,
		struct us_data*);

/* struct scsi_cmnd transfer buffer access utilities */
enum xfer_buf_dir	{TO_XFER_BUF, FROM_XFER_BUF};

extern unsigned int usb_stor_access_xfer_buf(unsigned char *buffer,
	unsigned int buflen, struct scsi_cmnd *srb, struct scatterlist **,
	unsigned int *offset, enum xfer_buf_dir dir);

extern void usb_stor_set_xfer_buf(unsigned char *buffer,
	unsigned int buflen, struct scsi_cmnd *srb);
#endif
t_for_req_done) from [<c02efd90>] (mmc_wait_for_cmd+0x64/0x84) [ 240.317953] [<c02efd90>] (mmc_wait_for_cmd) from [<c02f5b14>] (__mmc_switch+0xa4/0x2a8) [ 240.325964] [<c02f5b14>] (__mmc_switch) from [<c02f5d40>] (mmc_switch+0x28/0x30) [ 240.333389] [<c02f5d40>] (mmc_switch) from [<c02f0984>] (mmc_flush_cache+0x54/0x80) [ 240.341073] [<c02f0984>] (mmc_flush_cache) from [<c02ff0c4>] (mmc_blk_issue_rq+0x114/0x4e8) [ 240.349459] [<c02ff0c4>] (mmc_blk_issue_rq) from [<c03008d4>] (mmc_queue_thread+0xc0/0x180) [ 240.357844] [<c03008d4>] (mmc_queue_thread) from [<c003cf90>] (kthread+0xdc/0xf4) [ 240.365339] [<c003cf90>] (kthread) from [<c0010068>] (ret_from_fork+0x14/0x2c) .. .. [ 240.664311] INFO: task partprobe:564 blocked for more than 120 seconds. [ 240.670943] Not tainted 4.1.13-00510-g9d91424 #2 [ 240.676078] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 240.683922] partprobe D c047504c 0 564 486 0x00000000 [ 240.690318] [<c047504c>] (__schedule) from [<c04754a0>] (schedule+0x40/0x98) [ 240.697396] [<c04754a0>] (schedule) from [<c0477d40>] (schedule_timeout+0x148/0x188) [ 240.705149] [<c0477d40>] (schedule_timeout) from [<c0476040>] (wait_for_common+0xa4/0x170) [ 240.713446] [<c0476040>] (wait_for_common) from [<c01f3300>] (submit_bio_wait+0x58/0x64) [ 240.721571] [<c01f3300>] (submit_bio_wait) from [<c01fbbd8>] (blkdev_issue_flush+0x60/0x88) [ 240.729957] [<c01fbbd8>] (blkdev_issue_flush) from [<c010ff84>] (blkdev_fsync+0x34/0x44) [ 240.738083] [<c010ff84>] (blkdev_fsync) from [<c0109594>] (do_fsync+0x3c/0x64) [ 240.745319] [<c0109594>] (do_fsync) from [<c000ffc0>] (ret_fast_syscall+0x0/0x3c) .. Here is the detailed sequence showing when this issue may happen: 1) At probe time, mmci device is initialized and card busy detection based on DAT[0] monitoring is enabled. 2) Later during run time, since card reported to support internal caches, a MMCI_SWITCH command is sent to eMMC device with FLUSH_CACHE operation. On receiving this command, eMMC may enter busy state (for a relatively short time in the case of the dead-lock). 3) Then mmci interrupt is raised and mmci_irq() is called: MMCISTATUS register is read and is equal to 0x01000440. So the following status bits are set: - MCI_CMDRESPEND (= 6) - MCI_DATABLOCKEND (= 10) - MCI_ST_CARDBUSY (= 24) Since MMCIMASK0 register is 0x3FF, status variable is set to 0x00000040 and BIT MCI_CMDRESPEND is cleared by writing MMCICLEAR register. Then mmci_cmd_irq() is called. Considering the following conditions: - host->busy_status is 0, - this is a "busy response", - reading again MMCISTATUS register gives 0x1000400, MMCIMASK0 is updated to unmask MCI_ST_BUSYEND bit. Thus, MMCIMASK0 is set to 0x010003FF and host->busy_status is set to wait for busy end completion. Back again in status loop of mmci_irq(), we quickly go through mmci_data_irq() as there are no data in that case. And we finally go through following test at the end of while(status) loop: /* * Don't poll for busy completion in irq context. */ if (host->variant->busy_detect && host->busy_status) status &= ~host->variant->busy_detect_flag; Because status variable is not yet null (is equal to 0x40), we do not leave interrupt context yet but we loop again into while(status) loop. So we run across following steps: a) MMCISTATUS register is read again and this time is equal to 0x01000400. So that following bits are set: - MCI_DATABLOCKEND (= 10) - MCI_ST_CARDBUSY (= 24) Since MMCIMASK0 register is equal to 0x010003FF: b) status variable is set to 0x01000000. c) MCI_ST_CARDBUSY bit is cleared by writing MMCICLEAR register. Then, mmci_cmd_irq() is called one more time. Since host->busy_status is set and that MCI_ST_CARDBUSY is set in status variable, we just return from this function. Back again in mmci_irq(), status variable is set to 0 and we finally leave the while(status) loop. As a result we leave interrupt context, waiting for busy end interrupt event. Now, consider that busy end completion is raised IN BETWEEN steps 3.a) and 3.c). In such a case, we may mistakenly clear busy end interrupt at step 3.c) while it has not yet been processed. This will result in mmc command to wait forever for a busy end completion that will never happen. To fix the problem, this patch implements the following changes: Considering that the mmci seems to be triggering the IRQ on both edges while monitoring DAT0 for busy completion and that same status bit is used to monitor start and end of busy detection, special care must be taken to make sure that both start and end interrupts are always cleared one after the other. 1) Clearing of card busy bit is moved in mmc_cmd_irq() function where unmasking of busy end bit is effectively handled. 2) Just before unmasking busy end event, busy start event is cleared by writing card busy bit in MMCICLEAR register. 3) Finally, once we are no more busy with a command, busy end event is cleared writing again card busy bit in MMCICLEAR register. This patch has been tested with the ST Accordo5 machine, not yet supported upstream but relies on the mmci driver. Signed-off-by: Sarang Mairal <sarang.mairal@garmin.com> Signed-off-by: Jean-Nicolas Graux <jean-nicolas.graux@st.com> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Tested-by: Ulf Hansson <ulf.hansson@linaro.org> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Diffstat (limited to 'drivers/usb/gadget/udc/atmel_usba_udc.c')