From 74df43b3f626a3594a4de50556048852bf2753f7 Mon Sep 17 00:00:00 2001 From: Miquel Raynal Date: Tue, 28 Mar 2023 17:41:04 +0200 Subject: mtd: spi-nor: Enhance locking to support reads while writes On devices featuring several banks, the Read While Write (RWW) feature is here to improve the overall performance when performing parallel reads and writes at different locations (different banks). The following constraints have to be taken into account: 1#: A single operation can be performed in a given bank. 2#: Only a single program or erase operation can happen on the entire chip (common hardware limitation to limit costs) 3#: Reads must remain serialized even though reads crossing bank boundaries are allowed. 4#: The I/O bus is unique and thus is the most constrained resource, all spi-nor operations requiring access to the spi bus (through the spi controller) must be serialized until the bus exchanges are over. So we must ensure a single operation can be "sent" at a time. 5#: Any other operation that would not be either a read or a write or an erase is considered requiring access to the full chip and cannot be parallelized, we then need to ensure the full chip is in the idle state when this occurs. All these constraints can easily be managed with a proper locking model: 1#: Is enforced by a bitfield of the in-use banks, so that only a single operation can happen in a specific bank at any time. 2#: Is handled by the ongoing_pe boolean which is set before any write or erase, and is released only at the very end of the operation. This way, no other destructive operation on the chip can start during this time frame. 3#: An ongoing_rd boolean allows to track the ongoing reads, so that only one can be performed at a time. 4#: An ongoing_io boolean is introduced in order to capture and serialize bus accessed. This is the one being released "sooner" than before, because we only need to protect the chip against other SPI accesses during the I/O phase, which for the destructive operations is the beginning of the operation (when we send the command cycles and possibly the data), while the second part of the operation (the erase delay or the programmation delay) is when we can do something else in another bank. 5#: Is handled by the three booleans presented above, if any of them is set, the chip is not yet ready for the operation and must wait. All these internal variables are protected by the existing lock, so that changes in this structure are atomic. The serialization is handled with a wait queue. Signed-off-by: Miquel Raynal Link: https://lore.kernel.org/r/20230328154105.448540-8-miquel.raynal@bootlin.com Signed-off-by: Tudor Ambarus --- include/linux/mtd/spi-nor.h | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'include/linux/mtd/spi-nor.h') diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h index a3f8cdca90c8..82547b4b3708 100644 --- a/include/linux/mtd/spi-nor.h +++ b/include/linux/mtd/spi-nor.h @@ -343,6 +343,12 @@ struct spi_nor_flash_parameter; * struct spi_nor - Structure for defining the SPI NOR layer * @mtd: an mtd_info structure * @lock: the lock for the read/write/erase/lock/unlock operations + * @rww: Read-While-Write (RWW) sync lock + * @rww.wait: wait queue for the RWW sync + * @rww.ongoing_io: the bus is busy + * @rww.ongoing_rd: a read is ongoing on the chip + * @rww.ongoing_pe: a program/erase is ongoing on the chip + * @rww.used_banks: bitmap of the banks in use * @dev: pointer to an SPI device or an SPI NOR controller device * @spimem: pointer to the SPI memory device * @bouncebuf: bounce buffer used when the buffer passed by the MTD @@ -376,6 +382,13 @@ struct spi_nor_flash_parameter; struct spi_nor { struct mtd_info mtd; struct mutex lock; + struct spi_nor_rww { + wait_queue_head_t wait; + bool ongoing_io; + bool ongoing_rd; + bool ongoing_pe; + unsigned int used_banks; + } rww; struct device *dev; struct spi_mem *spimem; u8 *bouncebuf; -- cgit v1.2.3-70-g09d2 From 7fe1b00d92eaceb83f95200b5114cf5df0919892 Mon Sep 17 00:00:00 2001 From: Tudor Ambarus Date: Fri, 31 Mar 2023 07:46:03 +0000 Subject: mtd: spi-nor: Stop exporting spi_nor_restore() Some SPI NOR controllers that used this method were moved to drivers/spi/. We don't accept new support for the existing SPI NOR controllers drivers under drivers/mtd/spi-nor/controllers/ and we encourage their owners to move the drivers under drivers/spi/. Make spi_nor_restore() private as we're going to use it just in core.c. Link: https://lore.kernel.org/r/20230331074606.3559258-8-tudor.ambarus@linaro.org Signed-off-by: Tudor Ambarus --- Documentation/driver-api/mtd/spi-nor.rst | 3 --- drivers/mtd/spi-nor/core.c | 3 +-- include/linux/mtd/spi-nor.h | 6 ------ 3 files changed, 1 insertion(+), 11 deletions(-) (limited to 'include/linux/mtd/spi-nor.h') diff --git a/Documentation/driver-api/mtd/spi-nor.rst b/Documentation/driver-api/mtd/spi-nor.rst index 4a3adca417fd..c22f8c0f7950 100644 --- a/Documentation/driver-api/mtd/spi-nor.rst +++ b/Documentation/driver-api/mtd/spi-nor.rst @@ -63,6 +63,3 @@ The main API is spi_nor_scan(). Before you call the hook, a driver should initialize the necessary fields for spi_nor{}. Please see drivers/mtd/spi-nor/spi-nor.c for detail. Please also refer to spi-fsl-qspi.c when you want to write a new driver for a SPI NOR controller. -Another API is spi_nor_restore(), this is used to restore the status of SPI -flash chip such as addressing mode. Call it whenever detach the driver from -device or reboot the system. diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c index afb56b2cf8fe..75a7839af034 100644 --- a/drivers/mtd/spi-nor/core.c +++ b/drivers/mtd/spi-nor/core.c @@ -3291,7 +3291,7 @@ static void spi_nor_put_device(struct mtd_info *mtd) module_put(dev->driver->owner); } -void spi_nor_restore(struct spi_nor *nor) +static void spi_nor_restore(struct spi_nor *nor) { int ret; @@ -3311,7 +3311,6 @@ void spi_nor_restore(struct spi_nor *nor) if (nor->flags & SNOR_F_SOFT_RESET) spi_nor_soft_reset(nor); } -EXPORT_SYMBOL_GPL(spi_nor_restore); static const struct flash_info *spi_nor_match_name(struct spi_nor *nor, const char *name) diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h index 82547b4b3708..cdcfe0fd2e7d 100644 --- a/include/linux/mtd/spi-nor.h +++ b/include/linux/mtd/spi-nor.h @@ -450,10 +450,4 @@ static inline struct device_node *spi_nor_get_flash_node(struct spi_nor *nor) int spi_nor_scan(struct spi_nor *nor, const char *name, const struct spi_nor_hwcaps *hwcaps); -/** - * spi_nor_restore_addr_mode() - restore the status of SPI NOR - * @nor: the spi_nor structure - */ -void spi_nor_restore(struct spi_nor *nor); - #endif -- cgit v1.2.3-70-g09d2