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mtd: rawnand: Simplify the locking

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nand_get_device() was complex for apparently no good reason. Let's
replace this locking scheme with 2 mutexes: one attached to the
controller and another one attached to the chip.

Every time the core calls nand_get_device(), it will first lock the
chip and if the chip is not suspended, will then lock the controller.
nand_release_device() will release both lock in the reverse order.

nand_get_device() can sleep, just like the previous implementation,
which means you should never call that from an atomic context.

We also get rid of

- the chip->state field, since all it was used for was flagging the
  chip as suspended. We replace it by a field called chip->suspended
  and directly set it from nand_suspend/resume()
- the controller->wq and controller->active fields which are no longer
  needed since the new controller->lock (now a mutex) guarantees that
  all operations are serialized at the controller level
- panic_nand_get_device() which would anyway be a no-op. Talking about
  panic write, I keep thinking the rawnand implementation is unsafe
  because there's not negotiation with the controller to know when it's
  actually done with it's previous operation. I don't intend to fix
  that here, but that's probably something we should look at, or maybe
  we should consider dropping the ->_panic_write() implementation

Last important change to mention: we now return -EBUSY when someone
tries to access a device that as been suspended, and propagate this
error to the upper layer.

Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
This commit is contained in:
Boris Brezillon 2018-11-20 11:57:20 +01:00 committed by Miquel Raynal
parent 661803b233
commit 013e6292aa
2 changed files with 54 additions and 81 deletions
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109
drivers/mtd/nand/raw/nand_base.c
View File

@ -278,11 +278,8 @@ EXPORT_SYMBOL_GPL(nand_deselect_target);
static void nand_release_device(struct nand_chip *chip)
{
/* Release the controller and the chip */
spin_lock(&chip->controller->lock);
chip->controller->active = NULL;
chip->state = FL_READY;
wake_up(&chip->controller->wq);
spin_unlock(&chip->controller->lock);
mutex_unlock(&chip->controller->lock);
mutex_unlock(&chip->lock);
}
/**
@ -330,59 +327,25 @@ static int nand_isbad_bbm(struct nand_chip *chip, loff_t ofs)
return nand_block_bad(chip, ofs);
}
/**
* panic_nand_get_device - [GENERIC] Get chip for selected access
* @chip: the nand chip descriptor
* @new_state: the state which is requested
*
* Used when in panic, no locks are taken.
*/
static void panic_nand_get_device(struct nand_chip *chip, int new_state)
{
/* Hardware controller shared among independent devices */
chip->controller->active = chip;
chip->state = new_state;
}
/**
* nand_get_device - [GENERIC] Get chip for selected access
* @chip: NAND chip structure
* @new_state: the state which is requested
*
* Get the device and lock it for exclusive access
* Lock the device and its controller for exclusive access
*
* Return: -EBUSY if the chip has been suspended, 0 otherwise
*/
static int
nand_get_device(struct nand_chip *chip, int new_state)
static int nand_get_device(struct nand_chip *chip)
{
spinlock_t *lock = &chip->controller->lock;
wait_queue_head_t *wq = &chip->controller->wq;
DECLARE_WAITQUEUE(wait, current);
retry:
spin_lock(lock);
mutex_lock(&chip->lock);
if (chip->suspended) {
mutex_unlock(&chip->lock);
return -EBUSY;
}
mutex_lock(&chip->controller->lock);
/* Hardware controller shared among independent devices */
if (!chip->controller->active)
chip->controller->active = chip;
if (chip->controller->active == chip && chip->state == FL_READY) {
chip->state = new_state;
spin_unlock(lock);
return 0;
}
if (new_state == FL_PM_SUSPENDED) {
if (chip->controller->active->state == FL_PM_SUSPENDED) {
chip->state = FL_PM_SUSPENDED;
spin_unlock(lock);
return 0;
}
}
set_current_state(TASK_UNINTERRUPTIBLE);
add_wait_queue(wq, &wait);
spin_unlock(lock);
schedule();
remove_wait_queue(wq, &wait);
goto retry;
}
/**
* nand_check_wp - [GENERIC] check if the chip is write protected
@ -602,7 +565,10 @@ static int nand_block_markbad_lowlevel(struct nand_chip *chip, loff_t ofs)
nand_erase_nand(chip, &einfo, 0);
/* Write bad block marker to OOB */
nand_get_device(chip, FL_WRITING);
ret = nand_get_device(chip);
if (ret)
return ret;
ret = nand_markbad_bbm(chip, ofs);
nand_release_device(chip);
}
@ -3580,7 +3546,9 @@ static int nand_read_oob(struct mtd_info *mtd, loff_t from,
ops->mode != MTD_OPS_RAW)
return -ENOTSUPP;
nand_get_device(chip, FL_READING);
ret = nand_get_device(chip);
if (ret)
return ret;
if (!ops->datbuf)
ret = nand_do_read_oob(chip, from, ops);
@ -4099,9 +4067,6 @@ static int panic_nand_write(struct mtd_info *mtd, loff_t to, size_t len,
struct mtd_oob_ops ops;
int ret;
/* Grab the device */
panic_nand_get_device(chip, FL_WRITING);
nand_select_target(chip, chipnr);
/* Wait for the device to get ready */
@ -4132,7 +4097,9 @@ static int nand_write_oob(struct mtd_info *mtd, loff_t to,
ops->retlen = 0;
nand_get_device(chip, FL_WRITING);
ret = nand_get_device(chip);
if (ret)
return ret;
switch (ops->mode) {
case MTD_OPS_PLACE_OOB:
@ -4205,7 +4172,9 @@ int nand_erase_nand(struct nand_chip *chip, struct erase_info *instr,
return -EINVAL;
/* Grab the lock and see if the device is available */
nand_get_device(chip, FL_ERASING);
ret = nand_get_device(chip);
if (ret)
return ret;
/* Shift to get first page */
page = (int)(instr->addr >> chip->page_shift);
@ -4298,7 +4267,7 @@ static void nand_sync(struct mtd_info *mtd)
pr_debug("%s: called\n", __func__);
/* Grab the lock and see if the device is available */
nand_get_device(chip, FL_SYNCING);
WARN_ON(nand_get_device(chip));
/* Release it and go back */
nand_release_device(chip);
}
@ -4315,7 +4284,10 @@ static int nand_block_isbad(struct mtd_info *mtd, loff_t offs)
int ret;
/* Select the NAND device */
nand_get_device(chip, FL_READING);
ret = nand_get_device(chip);
if (ret)
return ret;
nand_select_target(chip, chipnr);
ret = nand_block_checkbad(chip, offs, 0);
@ -4388,7 +4360,13 @@ static int nand_max_bad_blocks(struct mtd_info *mtd, loff_t ofs, size_t len)
*/
static int nand_suspend(struct mtd_info *mtd)
{
return nand_get_device(mtd_to_nand(mtd), FL_PM_SUSPENDED);
struct nand_chip *chip = mtd_to_nand(mtd);
mutex_lock(&chip->lock);
chip->suspended = 1;
mutex_unlock(&chip->lock);
return 0;
}
/**
@ -4399,11 +4377,13 @@ static void nand_resume(struct mtd_info *mtd)
{
struct nand_chip *chip = mtd_to_nand(mtd);
if (chip->state == FL_PM_SUSPENDED)
nand_release_device(chip);
mutex_lock(&chip->lock);
if (chip->suspended)
chip->suspended = 0;
else
pr_err("%s called for a chip which is not in suspended state\n",
__func__);
mutex_unlock(&chip->lock);
}
/**
@ -4413,7 +4393,7 @@ static void nand_resume(struct mtd_info *mtd)
*/
static void nand_shutdown(struct mtd_info *mtd)
{
nand_get_device(mtd_to_nand(mtd), FL_PM_SUSPENDED);
nand_suspend(mtd);
}
/* Set default functions */
@ -5018,6 +4998,8 @@ static int nand_scan_ident(struct nand_chip *chip, unsigned int maxchips,
/* Assume all dies are deselected when we enter nand_scan_ident(). */
chip->cur_cs = -1;
mutex_init(&chip->lock);
/* Enforce the right timings for reset/detection */
onfi_fill_data_interface(chip, NAND_SDR_IFACE, 0);
@ -5717,9 +5699,6 @@ static int nand_scan_tail(struct nand_chip *chip)
}
chip->subpagesize = mtd->writesize >> mtd->subpage_sft;
/* Initialize state */
chip->state = FL_READY;
/* Invalidate the pagebuffer reference */
chip->pagebuf = -1;

24
include/linux/mtd/rawnand.h
View File

@ -16,13 +16,12 @@
#ifndef __LINUX_MTD_RAWNAND_H
#define __LINUX_MTD_RAWNAND_H
#include <linux/wait.h>
#include <linux/spinlock.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/flashchip.h>
#include <linux/mtd/bbm.h>
#include <linux/mtd/jedec.h>
#include <linux/mtd/onfi.h>
#include <linux/mutex.h>
#include <linux/of.h>
#include <linux/types.h>
@ -897,25 +896,17 @@ struct nand_controller_ops {
/**
* struct nand_controller - Structure used to describe a NAND controller
*
* @lock: protection lock
* @active: the mtd device which holds the controller currently
* @wq: wait queue to sleep on if a NAND operation is in
* progress used instead of the per chip wait queue
* when a hw controller is available.
* @lock: lock used to serialize accesses to the NAND controller
* @ops: NAND controller operations.
*/
struct nand_controller {
spinlock_t lock;
struct nand_chip *active;
wait_queue_head_t wq;
struct mutex lock;
const struct nand_controller_ops *ops;
};
static inline void nand_controller_init(struct nand_controller *nfc)
{
nfc->active = NULL;
spin_lock_init(&nfc->lock);
init_waitqueue_head(&nfc->wq);
mutex_init(&nfc->lock);
}
/**
@ -983,7 +974,6 @@ struct nand_legacy {
* setting the read-retry mode. Mostly needed for MLC NAND.
* @ecc: [BOARDSPECIFIC] ECC control structure
* @buf_align: minimum buffer alignment required by a platform
* @state: [INTERN] the current state of the NAND device
* @oob_poi: "poison value buffer," used for laying out OOB data
* before writing
* @page_shift: [INTERN] number of address bits in a page (column
@ -1034,6 +1024,9 @@ struct nand_legacy {
* cur_cs < numchips. NAND Controller drivers should not
* modify this value, but they're allowed to read it.
* @read_retries: [INTERN] the number of read retry modes supported
* @lock: lock protecting the suspended field. Also used to
* serialize accesses to the NAND device.
* @suspended: set to 1 when the device is suspended, 0 when it's not.
* @bbt: [INTERN] bad block table pointer
* @bbt_td: [REPLACEABLE] bad block table descriptor for flash
* lookup.
@ -1088,7 +1081,8 @@ struct nand_chip {
int read_retries;
flstate_t state;
struct mutex lock;
unsigned int suspended : 1;
uint8_t *oob_poi;
struct nand_controller *controller;