target/linux/bcm53xx/patches-4.14/180-spi-bcm-qspi-switch-back-to-reading-flash-using-smal.patch

   1 From: =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= <rafal@milecki.pl>
   2 Date: Thu, 11 Oct 2018 09:07:31 +0200
   3 Subject: [PATCH FIX] spi: bcm-qspi: switch back to reading flash using smaller
   4  chunks
   5 MIME-Version: 1.0
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   8
   9 Fixing/optimizing bcm_qspi_bspi_read() performance introduced two
  10 changes:
  11 1) It added a loop to read all requested data using multiple BSPI ops.
  12 2) It bumped max size of a single BSPI block request from 256 to 512 B.
  13
  14 The later change resulted in occasional BSPI timeouts causing a
  15 regression.
  16
  17 For some unknown reason hardware doesn't always handle reads as expected
  18 when using 512 B chunks. In such cases it may happen that BSPI returns
  19 amount of requested bytes without the last 1-3 ones. It provides the
  20 remaining bytes later but doesn't raise an interrupt until another LR
  21 start.
  22
  23 Switching back to 256 B reads fixes that problem and regression.
  24
  25 Fixes: 345309fa7c0c ("spi: bcm-qspi: Fix bcm_qspi_bspi_read() performance")
  26 Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
  27 Cc: stable@vger.kernel.org # 4.11+
  28 ---
  29  drivers/spi/spi-bcm-qspi.c | 2 +-
  30  1 file changed, 1 insertion(+), 1 deletion(-)
  31
  32 --- a/drivers/spi/spi-bcm-qspi.c
  33 +++ b/drivers/spi/spi-bcm-qspi.c
  34 @@ -88,7 +88,7 @@
  35  #define BSPI_BPP_MODE_SELECT_MASK              BIT(8)
  36  #define BSPI_BPP_ADDR_SELECT_MASK              BIT(16)
  37
  38 -#define BSPI_READ_LENGTH                       512
  39 +#define BSPI_READ_LENGTH                       256
  40
  41  /* MSPI register offsets */
  42  #define MSPI_SPCR0_LSB                         0x000