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Subject[PATCH] libata: implement support for 32-bit PIO transfers
Jeff,

here's an update of the patch. Rebuilt and re-tested against 2.6.25.
I've added Alan's previous Acked-by too btw.

Regards,
Willy


From 734d62ad5b63108bfc244433aedaf6190543e279 Mon Sep 17 00:00:00 2001
From: Willy Tarreau <w@1wt.eu>
Date: Thu, 17 Apr 2008 23:59:41 +0200
Subject: libata: implement support for 32-bit PIO transfers

This patch implements ATA_IOC_GET_IO32/ATA_IOC_SET_IO32 ioctls and
gets/sets the new ATA_DFLAG_32BIT_PIO ata flag accordingly for the
device. It only supports values 0 and 1 (disable/enable), as I have
no plan to implement the sync VLB transfers.

When ATA_DFLAG_32BIT_PIO is set in ata flags, PIO transfers will be
performed in 32-bit, just like with the plain old IDE drivers.

16-bit transfers in libata are as slow as 16-bit transfers in plain
old IDE drivers, which are about 35% slower than 32-bit transfers
with various CF and DOM. This patch restores the performance to
pre-libata level, which is a nice improvement for many small systems
relying on such hardware. On an ALIX board equipped with a 64 MB CF
card, transfer speed went up from 1.49 MB/sec to 2.41 MB/s, which
represents a net gain of 61%.

To enable 32-bit transfers, simply proceed like before with
IDE :

# hdparm -c 1 /dev/sda

Signed-off-by: Willy Tarreau <w@1wt.eu>
Acked-by: Alan Cox <alan@redhat.com>
---
drivers/ata/libata-core.c | 46 ++++++++++++++++++--------
drivers/ata/libata-scsi.c | 77 +++++++++++++++++++++++++++++++++++++-------
include/linux/libata.h | 1 +
3 files changed, 97 insertions(+), 27 deletions(-)
diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index be95fdb..22c2643 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -5036,7 +5036,7 @@ void swap_buf_le16(u16 *buf, unsigned int buf_words)
}

/**
- * ata_data_xfer - Transfer data by PIO
+ * ata_data_xfer - Transfer data by PIO (16 or 32-bit)
* @dev: device to target
* @buf: data buffer
* @buflen: buffer length
@@ -5055,30 +5055,48 @@ unsigned int ata_data_xfer(struct ata_device *dev, unsigned char *buf,
{
struct ata_port *ap = dev->link->ap;
void __iomem *data_addr = ap->ioaddr.data_addr;
- unsigned int words = buflen >> 1;
+ unsigned int words;

- /* Transfer multiple of 2 bytes */
- if (rw == READ)
- ioread16_rep(data_addr, buf, words);
- else
- iowrite16_rep(data_addr, buf, words);
+ if (dev->flags & ATA_DFLAG_32BIT_PIO) {
+ /* Transfer in 32-bit words */
+ words = buflen >> 2;
+ if (rw == READ)
+ ioread32_rep(data_addr, buf, words);
+ else
+ iowrite32_rep(data_addr, buf, words);
+ words <<= 2;
+ } else {
+ /* Transfer in 16-bit words */
+ words = buflen >> 1;
+ if (rw == READ)
+ ioread16_rep(data_addr, buf, words);
+ else
+ iowrite16_rep(data_addr, buf, words);
+ words <<= 1;
+ }

- /* Transfer trailing 1 byte, if any. */
- if (unlikely(buflen & 0x01)) {
+ /* Transfer trailing 1, 2 or 3 bytes, if any. We know how many bytes
+ * remain because <words> now contains the number of bytes transferred.
+ */
+ while (buflen > words) {
__le16 align_buf[1] = { 0 };
- unsigned char *trailing_buf = buf + buflen - 1;
+ unsigned char *trailing_buf = buf + words;
+ int len = buflen - words;
+
+ if (len > 2)
+ len = 2;

if (rw == READ) {
align_buf[0] = cpu_to_le16(ioread16(data_addr));
- memcpy(trailing_buf, align_buf, 1);
+ memcpy(trailing_buf, align_buf, len);
} else {
- memcpy(align_buf, trailing_buf, 1);
+ memcpy(align_buf, trailing_buf, len);
iowrite16(le16_to_cpu(align_buf[0]), data_addr);
}
- words++;
+ words += len;
}

- return words << 1;
+ return words;
}

/**
diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index 1579539..c0205de 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -448,22 +448,74 @@ int ata_task_ioctl(struct scsi_device *scsidev, void __user *arg)
return rc;
}

-int ata_scsi_ioctl(struct scsi_device *scsidev, int cmd, void __user *arg)
+/**
+ * ata_get_io32 - Handler for ATA_IOC_GET_IO32 ioctl
+ * @sdev: SCSI device to get identify data for
+ * @arg: User buffer area for return value
+ *
+ * LOCKING:
+ * Defined by the SCSI layer. We don't really care.
+ *
+ * RETURNS:
+ * Zero on success, negative errno on error.
+ */
+static int ata_get_io32(struct scsi_device *sdev, void __user *arg)
{
- int val = -EINVAL, rc = -EINVAL;
+ struct ata_port *ap = ata_shost_to_port(sdev->host);
+ struct ata_device *dev = ata_scsi_find_dev(ap, sdev);
+ int val;
+
+ if (!dev)
+ return -ENOMSG;
+
+ val = (dev->flags & ATA_DFLAG_32BIT_PIO) != 0;
+ if (copy_to_user(arg, &val, 1))
+ return -EFAULT;
+
+ return 0;
+}

+/**
+ * ata_set_io32 - Handler for ATA_IOC_SET_IO32 ioctl
+ * @sdev: SCSI device to get identify data for
+ * @arg: boolean integer value passed by user
+ *
+ * LOCKING:
+ * Defined by the SCSI layer. We don't really care.
+ *
+ * RETURNS:
+ * Zero on success, negative errno on error.
+ */
+static int ata_set_io32(struct scsi_device *sdev, void __user *arg)
+{
+ struct ata_port *ap = ata_shost_to_port(sdev->host);
+ struct ata_device *dev = ata_scsi_find_dev(ap, sdev);
+
+ if (!dev)
+ return -ENOMSG;
+
+ switch ((unsigned long) arg) {
+ case 0:
+ dev->flags &= ~ATA_DFLAG_32BIT_PIO;
+ return 0;
+ case 1:
+ dev->flags |= ATA_DFLAG_32BIT_PIO;
+ return 0;
+ default:
+ break;
+ }
+
+ return -EFAULT;
+}
+
+int ata_scsi_ioctl(struct scsi_device *scsidev, int cmd, void __user *arg)
+{
switch (cmd) {
case ATA_IOC_GET_IO32:
- val = 0;
- if (copy_to_user(arg, &val, 1))
- return -EFAULT;
- return 0;
+ return ata_get_io32(scsidev, arg);

case ATA_IOC_SET_IO32:
- val = (unsigned long) arg;
- if (val != 0)
- return -EINVAL;
- return 0;
+ return ata_set_io32(scsidev, arg);

case HDIO_GET_IDENTITY:
return ata_get_identity(scsidev, arg);
@@ -479,11 +531,10 @@ int ata_scsi_ioctl(struct scsi_device *scsidev, int cmd, void __user *arg)
return ata_task_ioctl(scsidev, arg);

default:
- rc = -ENOTTY;
- break;
+ return -ENOTTY;
}

- return rc;
+ return -EINVAL;
}

/**
diff --git a/include/linux/libata.h b/include/linux/libata.h
index 37ee881..1f1a9be 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -139,6 +139,7 @@ enum {
ATA_DFLAG_HIPM = (1 << 8), /* device supports HIPM */
ATA_DFLAG_DIPM = (1 << 9), /* device supports DIPM */
ATA_DFLAG_DMADIR = (1 << 10), /* device requires DMADIR */
+ ATA_DFLAG_32BIT_PIO = (1 << 11), /* device supports 32-bit in PIO mode */
ATA_DFLAG_CFG_MASK = (1 << 12) - 1,

ATA_DFLAG_PIO = (1 << 12), /* device limited to PIO mode */
--
1.5.3.8


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