87 lines
2.6 KiB
Diff
87 lines
2.6 KiB
Diff
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From 5ffa559b35dd90469e1f7fc21a77c6a2d5a8ca0f Mon Sep 17 00:00:00 2001
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From: Varadarajan Narayanan <varada@codeaurora.org>
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Date: Wed, 25 May 2016 13:40:03 +0530
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Subject: [PATCH 17/37] spi: qup: Fix sg nents calculation
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lib/scatterlist.c:sg_nents_for_len() returns the number of SG
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entries that total up to greater than or equal to the given
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length. However, the spi-qup driver assumed that the returned
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nents is for a total less than or equal to the given length. The
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spi-qup driver requests nents for SPI_MAX_XFER, however the API
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returns nents for SPI_MAX_XFER+delta (actually SZ_64K).
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Based on this, spi_qup_do_dma() calculates n_words and programs
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that into QUP_MX_{IN|OUT}PUT_CNT register. The calculated
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n_words value is more than the maximum value that can fit in the
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the 16-bit COUNT field of the QUP_MX_{IN|OUT}PUT_CNT register.
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And, the field gets programmed to zero. Since the COUNT field is
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zero, the i/o doesn't start eventually resulting in the i/o
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timing out.
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Signed-off-by: Varadarajan Narayanan <varada@codeaurora.org>
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---
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drivers/spi/spi-qup.c | 38 ++++++++++++++++++++++++++++++++++++--
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1 file changed, 36 insertions(+), 2 deletions(-)
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--- a/drivers/spi/spi-qup.c
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+++ b/drivers/spi/spi-qup.c
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@@ -581,6 +581,38 @@ static unsigned int spi_qup_sgl_get_size
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return length;
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}
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+/**
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+ * spi_qup_sg_nents_for_len - return total count of entries in scatterlist
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+ * needed to satisfy the supplied length
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+ * @sg: The scatterlist
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+ * @len: The total required length
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+ *
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+ * Description:
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+ * Determines the number of entries in sg that sum upto a maximum of
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+ * the supplied length, taking into acount chaining as well
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+ *
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+ * Returns:
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+ * the number of sg entries needed, negative error on failure
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+ *
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+ **/
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+int spi_qup_sg_nents_for_len(struct scatterlist *sg, u64 len)
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+{
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+ int nents;
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+ u64 total;
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+
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+ if (!len)
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+ return 0;
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+
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+ for (nents = 0, total = 0; sg; sg = sg_next(sg)) {
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+ nents++;
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+ total += sg_dma_len(sg);
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+ if (total > len)
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+ return (nents - 1);
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+ }
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+
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+ return -EINVAL;
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+}
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+
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static int spi_qup_do_dma(struct spi_device *spi, struct spi_transfer *xfer,
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unsigned long timeout)
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{
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@@ -597,7 +629,8 @@ unsigned long timeout)
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int rx_nents = 0, tx_nents = 0;
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if (rx_sgl) {
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- rx_nents = sg_nents_for_len(rx_sgl, SPI_MAX_XFER);
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+ rx_nents = spi_qup_sg_nents_for_len(rx_sgl,
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+ SPI_MAX_XFER);
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if (rx_nents < 0)
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rx_nents = sg_nents(rx_sgl);
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@@ -606,7 +639,8 @@ unsigned long timeout)
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}
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if (tx_sgl) {
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- tx_nents = sg_nents_for_len(tx_sgl, SPI_MAX_XFER);
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+ tx_nents = spi_qup_sg_nents_for_len(tx_sgl,
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+ SPI_MAX_XFER);
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if (tx_nents < 0)
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tx_nents = sg_nents(tx_sgl);
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