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Subject[PATCH 2/3] mtd: spi-nor: stm32-quadspi: fix prefetching outside fsize
Date
From: Ludovic Barre <ludovic.barre@st.com>

When memory-mapped mode is used, a prefetching mechanism fully
managed by the hardware allows to optimize the read from external
the QSPI memory. A 32-bytes FIFO is used for prefetching.
When the limit of flash size - fifo size is reached the prefetching
mechanism tries to read outside the fsize.
The stm32 quadspi hardware become busy and should be aborted.

Signed-off-by: Ludovic Barre <ludovic.barre@st.com>
Reported-by: Bruno Herrera <bruherrera@gmail.com>
Tested-by: Bruno Herrera <bruherrera@gmail.com>
---
drivers/mtd/spi-nor/stm32-quadspi.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/spi-nor/stm32-quadspi.c b/drivers/mtd/spi-nor/stm32-quadspi.c
index ad6a3e1..70710be 100644
--- a/drivers/mtd/spi-nor/stm32-quadspi.c
+++ b/drivers/mtd/spi-nor/stm32-quadspi.c
@@ -113,6 +113,7 @@
#define STM32_MAX_MMAP_SZ SZ_256M
#define STM32_MAX_NORCHIP 2

+#define STM32_QSPI_FIFO_SZ 32
#define STM32_QSPI_FIFO_TIMEOUT_US 30000
#define STM32_QSPI_BUSY_TIMEOUT_US 100000

@@ -124,6 +125,7 @@ struct stm32_qspi_flash {
u32 presc;
u32 read_mode;
bool registered;
+ u32 prefetch_limit;
};

struct stm32_qspi {
@@ -272,6 +274,7 @@ static int stm32_qspi_send(struct stm32_qspi_flash *flash,
{
struct stm32_qspi *qspi = flash->qspi;
u32 ccr, dcr, cr;
+ u32 last_byte;
int err;

err = stm32_qspi_wait_nobusy(qspi);
@@ -314,6 +317,10 @@ static int stm32_qspi_send(struct stm32_qspi_flash *flash,
if (err)
goto abort;
writel_relaxed(FCR_CTCF, qspi->io_base + QUADSPI_FCR);
+ } else {
+ last_byte = cmd->addr + cmd->len;
+ if (last_byte > flash->prefetch_limit)
+ goto abort;
}

return err;
@@ -322,7 +329,9 @@ static int stm32_qspi_send(struct stm32_qspi_flash *flash,
cr = readl_relaxed(qspi->io_base + QUADSPI_CR) | CR_ABORT;
writel_relaxed(cr, qspi->io_base + QUADSPI_CR);

- dev_err(qspi->dev, "%s abort err:%d\n", __func__, err);
+ if (err)
+ dev_err(qspi->dev, "%s abort err:%d\n", __func__, err);
+
return err;
}

@@ -550,6 +559,7 @@ static int stm32_qspi_flash_setup(struct stm32_qspi *qspi,
}

flash->fsize = FSIZE_VAL(mtd->size);
+ flash->prefetch_limit = mtd->size - STM32_QSPI_FIFO_SZ;

flash->read_mode = CCR_FMODE_MM;
if (mtd->size > qspi->mm_size)
--
2.7.4
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