target/linux/ipq806x/patches-4.9/0017-spi-qup-Fix-sg-nents-calculation.patch

   1 From 5ffa559b35dd90469e1f7fc21a77c6a2d5a8ca0f Mon Sep 17 00:00:00 2001
   2 From: Varadarajan Narayanan <varada@codeaurora.org>
   3 Date: Wed, 25 May 2016 13:40:03 +0530
   4 Subject: [PATCH 17/37] spi: qup: Fix sg nents calculation
   5
   6 lib/scatterlist.c:sg_nents_for_len() returns the number of SG
   7 entries that total up to greater than or equal to the given
   8 length. However, the spi-qup driver assumed that the returned
   9 nents is for a total less than or equal to the given length. The
  10 spi-qup driver requests nents for SPI_MAX_XFER, however the API
  11 returns nents for SPI_MAX_XFER+delta (actually SZ_64K).
  12
  13 Based on this, spi_qup_do_dma() calculates n_words and programs
  14 that into  QUP_MX_{IN|OUT}PUT_CNT register. The calculated
  15 n_words value is more than the maximum value that can fit in the
  16 the 16-bit COUNT field of the QUP_MX_{IN|OUT}PUT_CNT register.
  17 And, the field gets programmed to zero. Since the COUNT field is
  18 zero, the i/o doesn't start eventually resulting in the i/o
  19 timing out.
  20
  21 Signed-off-by: Varadarajan Narayanan <varada@codeaurora.org>
  22 ---
  23  drivers/spi/spi-qup.c |   38 ++++++++++++++++++++++++++++++++++++--
  24  1 file changed, 36 insertions(+), 2 deletions(-)
  25
  26 --- a/drivers/spi/spi-qup.c
  27 +++ b/drivers/spi/spi-qup.c
  28 @@ -581,6 +581,38 @@ static unsigned int spi_qup_sgl_get_size
  29         return length;
  30  }
  31
  32 +/**
  33 + * spi_qup_sg_nents_for_len - return total count of entries in scatterlist
  34 + *                           needed to satisfy the supplied length
  35 + * @sg:                The scatterlist
  36 + * @len:       The total required length
  37 + *
  38 + * Description:
  39 + * Determines the number of entries in sg that sum upto a maximum of
  40 + * the supplied length, taking into acount chaining as well
  41 + *
  42 + * Returns:
  43 + *   the number of sg entries needed, negative error on failure
  44 + *
  45 + **/
  46 +int spi_qup_sg_nents_for_len(struct scatterlist *sg, u64 len)
  47 +{
  48 +       int nents;
  49 +       u64 total;
  50 +
  51 +       if (!len)
  52 +               return 0;
  53 +
  54 +       for (nents = 0, total = 0; sg; sg = sg_next(sg)) {
  55 +               nents++;
  56 +               total += sg_dma_len(sg);
  57 +               if (total > len)
  58 +                       return (nents - 1);
  59 +       }
  60 +
  61 +       return -EINVAL;
  62 +}
  63 +
  64  static int spi_qup_do_dma(struct spi_device *spi, struct spi_transfer *xfer,
  65  unsigned long timeout)
  66  {
  67 @@ -597,7 +629,8 @@ unsigned long timeout)
  68                 int rx_nents = 0, tx_nents = 0;
  69
  70                 if (rx_sgl) {
  71 -                       rx_nents = sg_nents_for_len(rx_sgl, SPI_MAX_XFER);
  72 +                       rx_nents = spi_qup_sg_nents_for_len(rx_sgl,
  73 +                                                               SPI_MAX_XFER);
  74                         if (rx_nents < 0)
  75                                 rx_nents = sg_nents(rx_sgl);
  76
  77 @@ -606,7 +639,8 @@ unsigned long timeout)
  78                 }
  79
  80                 if (tx_sgl) {
  81 -                       tx_nents = sg_nents_for_len(tx_sgl, SPI_MAX_XFER);
  82 +                       tx_nents = spi_qup_sg_nents_for_len(tx_sgl,
  83 +                                                               SPI_MAX_XFER);
  84                         if (tx_nents < 0)
  85                                 tx_nents = sg_nents(tx_sgl);
  86