[PATCH v3 3/7] mtd: spi-nor: Add support for panic writes

[Paul Cercueil <paul.cercueil@bootlin.com>]

From: Tanmay Jagdale <tanmay@marvell.com>

If the SPI controller supports it, provide the functionality of doing a
panic write.

Update the spi-nor core code and controllers to make sure they won't try
to grab locked mutexes or sleep when doing a panic write, as preemption
and IRQs are disabled.

The information is carried down to the SPI controller driver through the
spi_mem_op structure. If the corresponding flag is set there, and the
SPI driver does support panic writes, it then has to respect the same
rules.

Signed-off-by: Tanmay Jagdale <tanmay@marvell.com>
Co-developed-by: Paul Cercueil <paul.cercueil@bootlin.com>
Signed-off-by: Paul Cercueil <paul.cercueil@bootlin.com>
---

Notes:
    v2: - Update spi_nor_wait_till_ready_with_timeout() to use
          poll_timeout_us_atomic() on panic
        - Alloc temp buffer with GFP_ATOMIC in spi_nor_octal_dtr_write()
          on panic
        - Bail out if nor->rww.ongoing_pe is set in spi_nor_panic_write()
    
    v3: Use GFP_KERNEL xor GFP_ATOMIC

 drivers/mtd/spi-nor/core.c | 75 +++++++++++++++++++++++++++++++++++---
 1 file changed, 70 insertions(+), 5 deletions(-)

diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
index 58257cc21c68..d5e572287bb7 100644
--- a/drivers/mtd/spi-nor/core.c
+++ b/drivers/mtd/spi-nor/core.c
@@ -97,6 +97,9 @@ void spi_nor_spimem_setup_op(const struct spi_nor *nor,
 	if (op->data.nbytes)
 		op->data.buswidth = spi_nor_get_protocol_data_nbits(proto);
 
+	if (nor->mtd.oops_panic_write)
+		op->panic_write = true;
+
 	if (spi_nor_protocol_is_dtr(proto)) {
 		/*
 		 * SPIMEM supports mixed DTR modes, but right now we can only
@@ -282,7 +285,7 @@ static ssize_t spi_nor_spimem_write_data(struct spi_nor *nor, loff_t to,
 	if (spi_nor_spimem_bounce(nor, &op))
 		memcpy(nor->bouncebuf, buf, op.data.nbytes);
 
-	if (nor->dirmap.wdesc) {
+	if (nor->dirmap.wdesc && !nor->mtd.oops_panic_write) {
 		nbytes = spi_mem_dirmap_write(nor->dirmap.wdesc, op.addr.val,
 					      op.data.nbytes, op.data.buf.out);
 	} else {
@@ -665,6 +668,9 @@ static void spi_nor_rww_end_rdst(struct spi_nor *nor)
 
 static int spi_nor_lock_rdst(struct spi_nor *nor)
 {
+	if (nor->mtd.oops_panic_write)
+		return 0;
+
 	if (spi_nor_use_parallel_locking(nor))
 		return spi_nor_rww_start_rdst(nor);
 
@@ -673,6 +679,9 @@ static int spi_nor_lock_rdst(struct spi_nor *nor)
 
 static void spi_nor_unlock_rdst(struct spi_nor *nor)
 {
+	if (nor->mtd.oops_panic_write)
+		return;
+
 	if (spi_nor_use_parallel_locking(nor)) {
 		spi_nor_rww_end_rdst(nor);
 		wake_up(&nor->rww.wait);
@@ -716,8 +725,14 @@ static int spi_nor_wait_till_ready_with_timeout(struct spi_nor *nor, u64 timeout
 {
 	int ret, status;
 
-	ret = poll_timeout_us(status = spi_nor_ready(nor), status,
-			      100, timeout_ms * 1000, false);
+	if (nor->mtd.oops_panic_write) {
+		ret = poll_timeout_us_atomic(status = spi_nor_ready(nor), status,
+					     100, timeout_ms * 1000, false);
+	} else {
+		ret = poll_timeout_us(status = spi_nor_ready(nor), status,
+				      100, timeout_ms * 1000, false);
+	}
+
 	if (ret < 0) {
 		dev_dbg(nor->dev, "flash operation timed out\n");
 		return ret;
@@ -1283,6 +1298,9 @@ static void spi_nor_rww_end_io(struct spi_nor *nor)
 
 static int spi_nor_lock_device(struct spi_nor *nor)
 {
+	if (nor->mtd.oops_panic_write)
+		return 0;
+
 	if (!spi_nor_use_parallel_locking(nor))
 		return 0;
 
@@ -1291,6 +1309,9 @@ static int spi_nor_lock_device(struct spi_nor *nor)
 
 static void spi_nor_unlock_device(struct spi_nor *nor)
 {
+	if (nor->mtd.oops_panic_write)
+		return;
+
 	if (spi_nor_use_parallel_locking(nor)) {
 		spi_nor_rww_end_io(nor);
 		wake_up(&nor->rww.wait);
@@ -1328,6 +1349,9 @@ int spi_nor_prep_and_lock(struct spi_nor *nor)
 {
 	int ret;
 
+	if (nor->mtd.oops_panic_write)
+		return 0;
+
 	ret = spi_nor_prep(nor);
 	if (ret)
 		return ret;
@@ -1343,6 +1367,9 @@ int spi_nor_prep_and_lock(struct spi_nor *nor)
 
 void spi_nor_unlock_and_unprep(struct spi_nor *nor)
 {
+	if (nor->mtd.oops_panic_write)
+		return;
+
 	if (!spi_nor_use_parallel_locking(nor)) {
 		mutex_unlock(&nor->lock);
 	} else {
@@ -1399,6 +1426,9 @@ static int spi_nor_prep_and_lock_pe(struct spi_nor *nor, loff_t start, size_t le
 {
 	int ret;
 
+	if (nor->mtd.oops_panic_write)
+		return 0;
+
 	ret = spi_nor_prep(nor);
 	if (ret)
 		return ret;
@@ -1414,6 +1444,9 @@ static int spi_nor_prep_and_lock_pe(struct spi_nor *nor, loff_t start, size_t le
 
 static void spi_nor_unlock_and_unprep_pe(struct spi_nor *nor, loff_t start, size_t len)
 {
+	if (nor->mtd.oops_panic_write)
+		return;
+
 	if (!spi_nor_use_parallel_locking(nor)) {
 		mutex_unlock(&nor->lock);
 	} else {
@@ -1472,6 +1505,9 @@ static int spi_nor_prep_and_lock_rd(struct spi_nor *nor, loff_t start, size_t le
 {
 	int ret;
 
+	if (nor->mtd.oops_panic_write)
+		return 0;
+
 	ret = spi_nor_prep(nor);
 	if (ret)
 		return ret;
@@ -1487,6 +1523,9 @@ static int spi_nor_prep_and_lock_rd(struct spi_nor *nor, loff_t start, size_t le
 
 static void spi_nor_unlock_and_unprep_rd(struct spi_nor *nor, loff_t start, size_t len)
 {
+	if (nor->mtd.oops_panic_write)
+		return;
+
 	if (!spi_nor_use_parallel_locking(nor)) {
 		mutex_unlock(&nor->lock);
 	} else {
@@ -2203,7 +2242,8 @@ static int spi_nor_octal_dtr_write(struct spi_nor *nor, loff_t to, size_t len,
 	if (IS_ALIGNED(to, 2) && IS_ALIGNED(len, 2))
 		return spi_nor_write_data(nor, to, len, buf);
 
-	tmp_buf = kmalloc(nor->params->page_size, GFP_KERNEL);
+	tmp_buf = kmalloc(nor->params->page_size,
+			  nor->mtd.oops_panic_write ? GFP_ATOMIC : GFP_KERNEL);
 	if (!tmp_buf)
 		return -ENOMEM;
 
@@ -3385,6 +3425,26 @@ static void spi_nor_soft_reset(struct spi_nor *nor)
 	usleep_range(SPI_NOR_SRST_SLEEP_MIN, SPI_NOR_SRST_SLEEP_MAX);
 }
 
+static int spi_nor_panic_write(struct mtd_info *mtd, loff_t to, size_t len,
+			       size_t *retlen, const u_char *buf)
+{
+	struct spi_nor *nor = mtd_to_spi_nor(mtd);
+
+	/*
+	 * At this point preemption and local interrupts are disabled, so we
+	 * can't get the lock if it's taken.
+	 */
+	if (mutex_is_locked(&nor->lock))
+		return -EPERM;
+
+	if (spi_nor_use_parallel_locking(nor) &&
+	    (nor->rww.ongoing_io || nor->rww.ongoing_rd || nor->rww.ongoing_pe)) {
+		return -EPERM;
+	}
+
+	return spi_nor_write(mtd, to, len, retlen, buf);
+}
+
 /* mtd suspend handler */
 static int spi_nor_suspend(struct mtd_info *mtd)
 {
@@ -3588,8 +3648,13 @@ static int spi_nor_set_mtd_info(struct spi_nor *nor)
 	mtd->size = nor->params->size;
 	mtd->_read = spi_nor_read;
 	/* Might be already set by some SST flashes. */
-	if (!mtd->_write)
+	if (!mtd->_write) {
 		mtd->_write = spi_nor_write;
+		if (nor->spimem &&
+		    spi_mem_controller_is_capable(nor->spimem->spi->controller, panic_write)) {
+			mtd->_panic_write = spi_nor_panic_write;
+		}
+	}
 	mtd->_suspend = spi_nor_suspend;
 	mtd->_resume = spi_nor_resume;
 	mtd->_get_device = spi_nor_get_device;
-- 
2.47.3