summaryrefslogtreecommitdiffstats
path: root/drivers/infiniband/hw/hfi1/pio_copy.c
diff options
context:
space:
mode:
Diffstat (limited to 'drivers/infiniband/hw/hfi1/pio_copy.c')
-rw-r--r--drivers/infiniband/hw/hfi1/pio_copy.c756
1 files changed, 756 insertions, 0 deletions
diff --git a/drivers/infiniband/hw/hfi1/pio_copy.c b/drivers/infiniband/hw/hfi1/pio_copy.c
new file mode 100644
index 000000000..4a4ec2397
--- /dev/null
+++ b/drivers/infiniband/hw/hfi1/pio_copy.c
@@ -0,0 +1,756 @@
+/*
+ * Copyright(c) 2015, 2016 Intel Corporation.
+ *
+ * This file is provided under a dual BSD/GPLv2 license. When using or
+ * redistributing this file, you may do so under either license.
+ *
+ * GPL LICENSE SUMMARY
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * BSD LICENSE
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in
+ * the documentation and/or other materials provided with the
+ * distribution.
+ * - Neither the name of Intel Corporation nor the names of its
+ * contributors may be used to endorse or promote products derived
+ * from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "hfi.h"
+
+/* additive distance between non-SOP and SOP space */
+#define SOP_DISTANCE (TXE_PIO_SIZE / 2)
+#define PIO_BLOCK_MASK (PIO_BLOCK_SIZE - 1)
+/* number of QUADWORDs in a block */
+#define PIO_BLOCK_QWS (PIO_BLOCK_SIZE / sizeof(u64))
+
+/**
+ * pio_copy - copy data block to MMIO space
+ * @pbuf: a number of blocks allocated within a PIO send context
+ * @pbc: PBC to send
+ * @from: source, must be 8 byte aligned
+ * @count: number of DWORD (32-bit) quantities to copy from source
+ *
+ * Copy data from source to PIO Send Buffer memory, 8 bytes at a time.
+ * Must always write full BLOCK_SIZE bytes blocks. The first block must
+ * be written to the corresponding SOP=1 address.
+ *
+ * Known:
+ * o pbuf->start always starts on a block boundary
+ * o pbuf can wrap only at a block boundary
+ */
+void pio_copy(struct hfi1_devdata *dd, struct pio_buf *pbuf, u64 pbc,
+ const void *from, size_t count)
+{
+ void __iomem *dest = pbuf->start + SOP_DISTANCE;
+ void __iomem *send = dest + PIO_BLOCK_SIZE;
+ void __iomem *dend; /* 8-byte data end */
+
+ /* write the PBC */
+ writeq(pbc, dest);
+ dest += sizeof(u64);
+
+ /* calculate where the QWORD data ends - in SOP=1 space */
+ dend = dest + ((count >> 1) * sizeof(u64));
+
+ if (dend < send) {
+ /*
+ * all QWORD data is within the SOP block, does *not*
+ * reach the end of the SOP block
+ */
+
+ while (dest < dend) {
+ writeq(*(u64 *)from, dest);
+ from += sizeof(u64);
+ dest += sizeof(u64);
+ }
+ /*
+ * No boundary checks are needed here:
+ * 0. We're not on the SOP block boundary
+ * 1. The possible DWORD dangle will still be within
+ * the SOP block
+ * 2. We cannot wrap except on a block boundary.
+ */
+ } else {
+ /* QWORD data extends _to_ or beyond the SOP block */
+
+ /* write 8-byte SOP chunk data */
+ while (dest < send) {
+ writeq(*(u64 *)from, dest);
+ from += sizeof(u64);
+ dest += sizeof(u64);
+ }
+ /* drop out of the SOP range */
+ dest -= SOP_DISTANCE;
+ dend -= SOP_DISTANCE;
+
+ /*
+ * If the wrap comes before or matches the data end,
+ * copy until until the wrap, then wrap.
+ *
+ * If the data ends at the end of the SOP above and
+ * the buffer wraps, then pbuf->end == dend == dest
+ * and nothing will get written, but we will wrap in
+ * case there is a dangling DWORD.
+ */
+ if (pbuf->end <= dend) {
+ while (dest < pbuf->end) {
+ writeq(*(u64 *)from, dest);
+ from += sizeof(u64);
+ dest += sizeof(u64);
+ }
+
+ dest -= pbuf->sc->size;
+ dend -= pbuf->sc->size;
+ }
+
+ /* write 8-byte non-SOP, non-wrap chunk data */
+ while (dest < dend) {
+ writeq(*(u64 *)from, dest);
+ from += sizeof(u64);
+ dest += sizeof(u64);
+ }
+ }
+ /* at this point we have wrapped if we are going to wrap */
+
+ /* write dangling u32, if any */
+ if (count & 1) {
+ union mix val;
+
+ val.val64 = 0;
+ val.val32[0] = *(u32 *)from;
+ writeq(val.val64, dest);
+ dest += sizeof(u64);
+ }
+ /*
+ * fill in rest of block, no need to check pbuf->end
+ * as we only wrap on a block boundary
+ */
+ while (((unsigned long)dest & PIO_BLOCK_MASK) != 0) {
+ writeq(0, dest);
+ dest += sizeof(u64);
+ }
+
+ /* finished with this buffer */
+ this_cpu_dec(*pbuf->sc->buffers_allocated);
+ preempt_enable();
+}
+
+/*
+ * Handle carry bytes using shifts and masks.
+ *
+ * NOTE: the value the unused portion of carry is expected to always be zero.
+ */
+
+/*
+ * "zero" shift - bit shift used to zero out upper bytes. Input is
+ * the count of LSB bytes to preserve.
+ */
+#define zshift(x) (8 * (8 - (x)))
+
+/*
+ * "merge" shift - bit shift used to merge with carry bytes. Input is
+ * the LSB byte count to move beyond.
+ */
+#define mshift(x) (8 * (x))
+
+/*
+ * Jump copy - no-loop copy for < 8 bytes.
+ */
+static inline void jcopy(u8 *dest, const u8 *src, u32 n)
+{
+ switch (n) {
+ case 7:
+ *dest++ = *src++;
+ fallthrough;
+ case 6:
+ *dest++ = *src++;
+ fallthrough;
+ case 5:
+ *dest++ = *src++;
+ fallthrough;
+ case 4:
+ *dest++ = *src++;
+ fallthrough;
+ case 3:
+ *dest++ = *src++;
+ fallthrough;
+ case 2:
+ *dest++ = *src++;
+ fallthrough;
+ case 1:
+ *dest++ = *src++;
+ }
+}
+
+/*
+ * Read nbytes from "from" and and place them in the low bytes
+ * of pbuf->carry. Other bytes are left as-is. Any previous
+ * value in pbuf->carry is lost.
+ *
+ * NOTES:
+ * o do not read from from if nbytes is zero
+ * o from may _not_ be u64 aligned.
+ */
+static inline void read_low_bytes(struct pio_buf *pbuf, const void *from,
+ unsigned int nbytes)
+{
+ pbuf->carry.val64 = 0;
+ jcopy(&pbuf->carry.val8[0], from, nbytes);
+ pbuf->carry_bytes = nbytes;
+}
+
+/*
+ * Read nbytes bytes from "from" and put them at the end of pbuf->carry.
+ * It is expected that the extra read does not overfill carry.
+ *
+ * NOTES:
+ * o from may _not_ be u64 aligned
+ * o nbytes may span a QW boundary
+ */
+static inline void read_extra_bytes(struct pio_buf *pbuf,
+ const void *from, unsigned int nbytes)
+{
+ jcopy(&pbuf->carry.val8[pbuf->carry_bytes], from, nbytes);
+ pbuf->carry_bytes += nbytes;
+}
+
+/*
+ * Write a quad word using parts of pbuf->carry and the next 8 bytes of src.
+ * Put the unused part of the next 8 bytes of src into the LSB bytes of
+ * pbuf->carry with the upper bytes zeroed..
+ *
+ * NOTES:
+ * o result must keep unused bytes zeroed
+ * o src must be u64 aligned
+ */
+static inline void merge_write8(
+ struct pio_buf *pbuf,
+ void __iomem *dest,
+ const void *src)
+{
+ u64 new, temp;
+
+ new = *(u64 *)src;
+ temp = pbuf->carry.val64 | (new << mshift(pbuf->carry_bytes));
+ writeq(temp, dest);
+ pbuf->carry.val64 = new >> zshift(pbuf->carry_bytes);
+}
+
+/*
+ * Write a quad word using all bytes of carry.
+ */
+static inline void carry8_write8(union mix carry, void __iomem *dest)
+{
+ writeq(carry.val64, dest);
+}
+
+/*
+ * Write a quad word using all the valid bytes of carry. If carry
+ * has zero valid bytes, nothing is written.
+ * Returns 0 on nothing written, non-zero on quad word written.
+ */
+static inline int carry_write8(struct pio_buf *pbuf, void __iomem *dest)
+{
+ if (pbuf->carry_bytes) {
+ /* unused bytes are always kept zeroed, so just write */
+ writeq(pbuf->carry.val64, dest);
+ return 1;
+ }
+
+ return 0;
+}
+
+/*
+ * Segmented PIO Copy - start
+ *
+ * Start a PIO copy.
+ *
+ * @pbuf: destination buffer
+ * @pbc: the PBC for the PIO buffer
+ * @from: data source, QWORD aligned
+ * @nbytes: bytes to copy
+ */
+void seg_pio_copy_start(struct pio_buf *pbuf, u64 pbc,
+ const void *from, size_t nbytes)
+{
+ void __iomem *dest = pbuf->start + SOP_DISTANCE;
+ void __iomem *send = dest + PIO_BLOCK_SIZE;
+ void __iomem *dend; /* 8-byte data end */
+
+ writeq(pbc, dest);
+ dest += sizeof(u64);
+
+ /* calculate where the QWORD data ends - in SOP=1 space */
+ dend = dest + ((nbytes >> 3) * sizeof(u64));
+
+ if (dend < send) {
+ /*
+ * all QWORD data is within the SOP block, does *not*
+ * reach the end of the SOP block
+ */
+
+ while (dest < dend) {
+ writeq(*(u64 *)from, dest);
+ from += sizeof(u64);
+ dest += sizeof(u64);
+ }
+ /*
+ * No boundary checks are needed here:
+ * 0. We're not on the SOP block boundary
+ * 1. The possible DWORD dangle will still be within
+ * the SOP block
+ * 2. We cannot wrap except on a block boundary.
+ */
+ } else {
+ /* QWORD data extends _to_ or beyond the SOP block */
+
+ /* write 8-byte SOP chunk data */
+ while (dest < send) {
+ writeq(*(u64 *)from, dest);
+ from += sizeof(u64);
+ dest += sizeof(u64);
+ }
+ /* drop out of the SOP range */
+ dest -= SOP_DISTANCE;
+ dend -= SOP_DISTANCE;
+
+ /*
+ * If the wrap comes before or matches the data end,
+ * copy until until the wrap, then wrap.
+ *
+ * If the data ends at the end of the SOP above and
+ * the buffer wraps, then pbuf->end == dend == dest
+ * and nothing will get written, but we will wrap in
+ * case there is a dangling DWORD.
+ */
+ if (pbuf->end <= dend) {
+ while (dest < pbuf->end) {
+ writeq(*(u64 *)from, dest);
+ from += sizeof(u64);
+ dest += sizeof(u64);
+ }
+
+ dest -= pbuf->sc->size;
+ dend -= pbuf->sc->size;
+ }
+
+ /* write 8-byte non-SOP, non-wrap chunk data */
+ while (dest < dend) {
+ writeq(*(u64 *)from, dest);
+ from += sizeof(u64);
+ dest += sizeof(u64);
+ }
+ }
+ /* at this point we have wrapped if we are going to wrap */
+
+ /* ...but it doesn't matter as we're done writing */
+
+ /* save dangling bytes, if any */
+ read_low_bytes(pbuf, from, nbytes & 0x7);
+
+ pbuf->qw_written = 1 /*PBC*/ + (nbytes >> 3);
+}
+
+/*
+ * Mid copy helper, "mixed case" - source is 64-bit aligned but carry
+ * bytes are non-zero.
+ *
+ * Whole u64s must be written to the chip, so bytes must be manually merged.
+ *
+ * @pbuf: destination buffer
+ * @from: data source, is QWORD aligned.
+ * @nbytes: bytes to copy
+ *
+ * Must handle nbytes < 8.
+ */
+static void mid_copy_mix(struct pio_buf *pbuf, const void *from, size_t nbytes)
+{
+ void __iomem *dest = pbuf->start + (pbuf->qw_written * sizeof(u64));
+ void __iomem *dend; /* 8-byte data end */
+ unsigned long qw_to_write = nbytes >> 3;
+ unsigned long bytes_left = nbytes & 0x7;
+
+ /* calculate 8-byte data end */
+ dend = dest + (qw_to_write * sizeof(u64));
+
+ if (pbuf->qw_written < PIO_BLOCK_QWS) {
+ /*
+ * Still within SOP block. We don't need to check for
+ * wrap because we are still in the first block and
+ * can only wrap on block boundaries.
+ */
+ void __iomem *send; /* SOP end */
+ void __iomem *xend;
+
+ /*
+ * calculate the end of data or end of block, whichever
+ * comes first
+ */
+ send = pbuf->start + PIO_BLOCK_SIZE;
+ xend = min(send, dend);
+
+ /* shift up to SOP=1 space */
+ dest += SOP_DISTANCE;
+ xend += SOP_DISTANCE;
+
+ /* write 8-byte chunk data */
+ while (dest < xend) {
+ merge_write8(pbuf, dest, from);
+ from += sizeof(u64);
+ dest += sizeof(u64);
+ }
+
+ /* shift down to SOP=0 space */
+ dest -= SOP_DISTANCE;
+ }
+ /*
+ * At this point dest could be (either, both, or neither):
+ * - at dend
+ * - at the wrap
+ */
+
+ /*
+ * If the wrap comes before or matches the data end,
+ * copy until until the wrap, then wrap.
+ *
+ * If dest is at the wrap, we will fall into the if,
+ * not do the loop, when wrap.
+ *
+ * If the data ends at the end of the SOP above and
+ * the buffer wraps, then pbuf->end == dend == dest
+ * and nothing will get written.
+ */
+ if (pbuf->end <= dend) {
+ while (dest < pbuf->end) {
+ merge_write8(pbuf, dest, from);
+ from += sizeof(u64);
+ dest += sizeof(u64);
+ }
+
+ dest -= pbuf->sc->size;
+ dend -= pbuf->sc->size;
+ }
+
+ /* write 8-byte non-SOP, non-wrap chunk data */
+ while (dest < dend) {
+ merge_write8(pbuf, dest, from);
+ from += sizeof(u64);
+ dest += sizeof(u64);
+ }
+
+ pbuf->qw_written += qw_to_write;
+
+ /* handle carry and left-over bytes */
+ if (pbuf->carry_bytes + bytes_left >= 8) {
+ unsigned long nread;
+
+ /* there is enough to fill another qw - fill carry */
+ nread = 8 - pbuf->carry_bytes;
+ read_extra_bytes(pbuf, from, nread);
+
+ /*
+ * One more write - but need to make sure dest is correct.
+ * Check for wrap and the possibility the write
+ * should be in SOP space.
+ *
+ * The two checks immediately below cannot both be true, hence
+ * the else. If we have wrapped, we cannot still be within the
+ * first block. Conversely, if we are still in the first block,
+ * we cannot have wrapped. We do the wrap check first as that
+ * is more likely.
+ */
+ /* adjust if we have wrapped */
+ if (dest >= pbuf->end)
+ dest -= pbuf->sc->size;
+ /* jump to the SOP range if within the first block */
+ else if (pbuf->qw_written < PIO_BLOCK_QWS)
+ dest += SOP_DISTANCE;
+
+ /* flush out full carry */
+ carry8_write8(pbuf->carry, dest);
+ pbuf->qw_written++;
+
+ /* now adjust and read the rest of the bytes into carry */
+ bytes_left -= nread;
+ from += nread; /* from is now not aligned */
+ read_low_bytes(pbuf, from, bytes_left);
+ } else {
+ /* not enough to fill another qw, append the rest to carry */
+ read_extra_bytes(pbuf, from, bytes_left);
+ }
+}
+
+/*
+ * Mid copy helper, "straight case" - source pointer is 64-bit aligned
+ * with no carry bytes.
+ *
+ * @pbuf: destination buffer
+ * @from: data source, is QWORD aligned
+ * @nbytes: bytes to copy
+ *
+ * Must handle nbytes < 8.
+ */
+static void mid_copy_straight(struct pio_buf *pbuf,
+ const void *from, size_t nbytes)
+{
+ void __iomem *dest = pbuf->start + (pbuf->qw_written * sizeof(u64));
+ void __iomem *dend; /* 8-byte data end */
+
+ /* calculate 8-byte data end */
+ dend = dest + ((nbytes >> 3) * sizeof(u64));
+
+ if (pbuf->qw_written < PIO_BLOCK_QWS) {
+ /*
+ * Still within SOP block. We don't need to check for
+ * wrap because we are still in the first block and
+ * can only wrap on block boundaries.
+ */
+ void __iomem *send; /* SOP end */
+ void __iomem *xend;
+
+ /*
+ * calculate the end of data or end of block, whichever
+ * comes first
+ */
+ send = pbuf->start + PIO_BLOCK_SIZE;
+ xend = min(send, dend);
+
+ /* shift up to SOP=1 space */
+ dest += SOP_DISTANCE;
+ xend += SOP_DISTANCE;
+
+ /* write 8-byte chunk data */
+ while (dest < xend) {
+ writeq(*(u64 *)from, dest);
+ from += sizeof(u64);
+ dest += sizeof(u64);
+ }
+
+ /* shift down to SOP=0 space */
+ dest -= SOP_DISTANCE;
+ }
+ /*
+ * At this point dest could be (either, both, or neither):
+ * - at dend
+ * - at the wrap
+ */
+
+ /*
+ * If the wrap comes before or matches the data end,
+ * copy until until the wrap, then wrap.
+ *
+ * If dest is at the wrap, we will fall into the if,
+ * not do the loop, when wrap.
+ *
+ * If the data ends at the end of the SOP above and
+ * the buffer wraps, then pbuf->end == dend == dest
+ * and nothing will get written.
+ */
+ if (pbuf->end <= dend) {
+ while (dest < pbuf->end) {
+ writeq(*(u64 *)from, dest);
+ from += sizeof(u64);
+ dest += sizeof(u64);
+ }
+
+ dest -= pbuf->sc->size;
+ dend -= pbuf->sc->size;
+ }
+
+ /* write 8-byte non-SOP, non-wrap chunk data */
+ while (dest < dend) {
+ writeq(*(u64 *)from, dest);
+ from += sizeof(u64);
+ dest += sizeof(u64);
+ }
+
+ /* we know carry_bytes was zero on entry to this routine */
+ read_low_bytes(pbuf, from, nbytes & 0x7);
+
+ pbuf->qw_written += nbytes >> 3;
+}
+
+/*
+ * Segmented PIO Copy - middle
+ *
+ * Must handle any aligned tail and any aligned source with any byte count.
+ *
+ * @pbuf: a number of blocks allocated within a PIO send context
+ * @from: data source
+ * @nbytes: number of bytes to copy
+ */
+void seg_pio_copy_mid(struct pio_buf *pbuf, const void *from, size_t nbytes)
+{
+ unsigned long from_align = (unsigned long)from & 0x7;
+
+ if (pbuf->carry_bytes + nbytes < 8) {
+ /* not enough bytes to fill a QW */
+ read_extra_bytes(pbuf, from, nbytes);
+ return;
+ }
+
+ if (from_align) {
+ /* misaligned source pointer - align it */
+ unsigned long to_align;
+
+ /* bytes to read to align "from" */
+ to_align = 8 - from_align;
+
+ /*
+ * In the advance-to-alignment logic below, we do not need
+ * to check if we are using more than nbytes. This is because
+ * if we are here, we already know that carry+nbytes will
+ * fill at least one QW.
+ */
+ if (pbuf->carry_bytes + to_align < 8) {
+ /* not enough align bytes to fill a QW */
+ read_extra_bytes(pbuf, from, to_align);
+ from += to_align;
+ nbytes -= to_align;
+ } else {
+ /* bytes to fill carry */
+ unsigned long to_fill = 8 - pbuf->carry_bytes;
+ /* bytes left over to be read */
+ unsigned long extra = to_align - to_fill;
+ void __iomem *dest;
+
+ /* fill carry... */
+ read_extra_bytes(pbuf, from, to_fill);
+ from += to_fill;
+ nbytes -= to_fill;
+ /* may not be enough valid bytes left to align */
+ if (extra > nbytes)
+ extra = nbytes;
+
+ /* ...now write carry */
+ dest = pbuf->start + (pbuf->qw_written * sizeof(u64));
+
+ /*
+ * The two checks immediately below cannot both be
+ * true, hence the else. If we have wrapped, we
+ * cannot still be within the first block.
+ * Conversely, if we are still in the first block, we
+ * cannot have wrapped. We do the wrap check first
+ * as that is more likely.
+ */
+ /* adjust if we've wrapped */
+ if (dest >= pbuf->end)
+ dest -= pbuf->sc->size;
+ /* jump to SOP range if within the first block */
+ else if (pbuf->qw_written < PIO_BLOCK_QWS)
+ dest += SOP_DISTANCE;
+
+ carry8_write8(pbuf->carry, dest);
+ pbuf->qw_written++;
+
+ /* read any extra bytes to do final alignment */
+ /* this will overwrite anything in pbuf->carry */
+ read_low_bytes(pbuf, from, extra);
+ from += extra;
+ nbytes -= extra;
+ /*
+ * If no bytes are left, return early - we are done.
+ * NOTE: This short-circuit is *required* because
+ * "extra" may have been reduced in size and "from"
+ * is not aligned, as required when leaving this
+ * if block.
+ */
+ if (nbytes == 0)
+ return;
+ }
+
+ /* at this point, from is QW aligned */
+ }
+
+ if (pbuf->carry_bytes)
+ mid_copy_mix(pbuf, from, nbytes);
+ else
+ mid_copy_straight(pbuf, from, nbytes);
+}
+
+/*
+ * Segmented PIO Copy - end
+ *
+ * Write any remainder (in pbuf->carry) and finish writing the whole block.
+ *
+ * @pbuf: a number of blocks allocated within a PIO send context
+ */
+void seg_pio_copy_end(struct pio_buf *pbuf)
+{
+ void __iomem *dest = pbuf->start + (pbuf->qw_written * sizeof(u64));
+
+ /*
+ * The two checks immediately below cannot both be true, hence the
+ * else. If we have wrapped, we cannot still be within the first
+ * block. Conversely, if we are still in the first block, we
+ * cannot have wrapped. We do the wrap check first as that is
+ * more likely.
+ */
+ /* adjust if we have wrapped */
+ if (dest >= pbuf->end)
+ dest -= pbuf->sc->size;
+ /* jump to the SOP range if within the first block */
+ else if (pbuf->qw_written < PIO_BLOCK_QWS)
+ dest += SOP_DISTANCE;
+
+ /* write final bytes, if any */
+ if (carry_write8(pbuf, dest)) {
+ dest += sizeof(u64);
+ /*
+ * NOTE: We do not need to recalculate whether dest needs
+ * SOP_DISTANCE or not.
+ *
+ * If we are in the first block and the dangle write
+ * keeps us in the same block, dest will need
+ * to retain SOP_DISTANCE in the loop below.
+ *
+ * If we are in the first block and the dangle write pushes
+ * us to the next block, then loop below will not run
+ * and dest is not used. Hence we do not need to update
+ * it.
+ *
+ * If we are past the first block, then SOP_DISTANCE
+ * was never added, so there is nothing to do.
+ */
+ }
+
+ /* fill in rest of block */
+ while (((unsigned long)dest & PIO_BLOCK_MASK) != 0) {
+ writeq(0, dest);
+ dest += sizeof(u64);
+ }
+
+ /* finished with this buffer */
+ this_cpu_dec(*pbuf->sc->buffers_allocated);
+ preempt_enable();
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-01 11:29:28 +0000