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spi: bcm-qspi: switch back to reading flash using smaller chunks

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commit 940ec770c295682993d1cccce3081fd7c74fece8 upstream.

Fixing/optimizing bcm_qspi_bspi_read() performance introduced two
changes:
1) It added a loop to read all requested data using multiple BSPI ops.
2) It bumped max size of a single BSPI block request from 256 to 512 B.

The later change resulted in occasional BSPI timeouts causing a
regression.

For some unknown reason hardware doesn't always handle reads as expected
when using 512 B chunks. In such cases it may happen that BSPI returns
amount of requested bytes without the last 1-3 ones. It provides the
remaining bytes later but doesn't raise an interrupt until another LR
start.

Switching back to 256 B reads fixes that problem and regression.

Fixes: 345309fa7c0c ("spi: bcm-qspi: Fix bcm_qspi_bspi_read() performance")
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Rafał Miłecki 2018-10-11 09:42:17 +02:00 committed by Greg Kroah-Hartman
parent 31354285b2
commit 615bda31cc
1 changed files with 1 additions and 1 deletions
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2
drivers/spi/spi-bcm-qspi.c
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@ -88,7 +88,7 @@
#define BSPI_BPP_MODE_SELECT_MASK BIT(8)
#define BSPI_BPP_ADDR_SELECT_MASK BIT(16)
#define BSPI_READ_LENGTH 512
#define BSPI_READ_LENGTH 256
/* MSPI register offsets */
#define MSPI_SPCR0_LSB 0x000