spi: stm32-qspi: Increase read throughput in indirect mode

When WATCHDOG_RESET() was replaced by schedule() in commit
29caf9305b6f ("cyclic: Use schedule() instead of WATCHDOG_RESET()")
we not only reset the watchdog but also call the cyclic infrastructure
which takes time and has impact on read accesses performances.

Move schedule() from _stm32_qspi_read_fifo() to _stm32_qspi_poll()
and call schedule() only every 1MB chunk of data.

Test performed by reading 64MB on sNOR on stm32mp157c-ev1 board:

          before      after    ratio
Read  :  201 KB/s    520KB/s   +258%

Reviewed-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>

diff --git a/drivers/spi/stm32_qspi.c b/drivers/spi/stm32_qspi.c
index 3216ec8010e275ce28e384c312d54bc6058e02d2..1778f8c145861f71797c54b0371630a0deb307af 100644 (file)
--- a/drivers/spi/stm32_qspi.c
+++ b/drivers/spi/stm32_qspi.c
@@ -165,7 +165,6 @@ static int _stm32_qspi_wait_cmd(struct stm32_qspi_priv *priv,
 static void _stm32_qspi_read_fifo(u8 *val, void __iomem *addr)
 {
        *val = readb(addr);
-       schedule();
 }
 
 static void _stm32_qspi_write_fifo(u8 *val, void __iomem *addr)
@@ -200,6 +199,9 @@ static int _stm32_qspi_poll(struct stm32_qspi_priv *priv,
                }
 
                fifo(buf++, &priv->regs->dr);
+
+               if (!(len % SZ_1M))
+                       schedule();
        }
 
        return 0;