[PATCH 2/3] mtd: spi-nor: stm32-quadspi: fix prefetching outside fsize

[Ludovic Barre]

From: Ludovic Barre <ludovic.ba...@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.ba...@st.com>
Reported-by: Bruno Herrera <bruherr...@gmail.com>
Tested-by: Bruno Herrera <bruherr...@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