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SubjectRe: [PATCH 3/3] faster workaround
Date
This is based on a patch from Jeff from 2004, but backported to 2.6.23 and 
furthermore, it will use the 7.5kiB/512B splitoff for blacklisted drives
only.

Jeff, why did you replace ATA_SHT_USE_CLUSTERING and ATA_DMA_BOUNDARY?

drivers/ata/libata-core.c | 9 ++++-
drivers/ata/sata_sil.c | 58 ++++++++++++++++++++++++++++++------
include/linux/libata.h | 6 +++
3 files changed, 62 insertions(+), 11 deletions(-)

Signed-off-by: Bernd Schubert <bs@q-leap.de>


Index: linux-2.6.23-rc9/drivers/ata/libata-core.c
===================================================================
--- linux-2.6.23-rc9.orig/drivers/ata/libata-core.c 2007-10-02
17:21:12.000000000 +0200
+++ linux-2.6.23-rc9/drivers/ata/libata-core.c 2007-10-11 10:46:18.000000000
+0200
@@ -4073,7 +4073,7 @@ void ata_sg_clean(struct ata_queued_cmd
* spin_lock_irqsave(host lock)
*
*/
-static void ata_fill_sg(struct ata_queued_cmd *qc)
+void ata_fill_sg(struct ata_queued_cmd *qc)
{
struct ata_port *ap = qc->ap;
struct scatterlist *sg;
@@ -4217,10 +4217,15 @@ int ata_check_atapi_dma(struct ata_queue
*/
void ata_qc_prep(struct ata_queued_cmd *qc)
{
+ struct ata_port *ap = qc->ap;
+
if (!(qc->flags & ATA_QCFLAG_DMAMAP))
return;

- ata_fill_sg(qc);
+ if (ap->ops->fill_sg)
+ ap->ops->fill_sg(qc);
+ else
+ ata_fill_sg(qc);
}

/**
Index: linux-2.6.23-rc9/drivers/ata/sata_sil.c
===================================================================
--- linux-2.6.23-rc9.orig/drivers/ata/sata_sil.c 2007-10-11 10:45:08.000000000
+0200
+++ linux-2.6.23-rc9/drivers/ata/sata_sil.c 2007-10-11 10:57:51.000000000
+0200
@@ -120,6 +120,7 @@ static int sil_scr_write(struct ata_port
static int sil_set_mode (struct ata_port *ap, struct ata_device **r_failed);
static void sil_freeze(struct ata_port *ap);
static void sil_thaw(struct ata_port *ap);
+static void sil_fill_sg(struct ata_queued_cmd *qc);


static const struct pci_device_id sil_pci_tbl[] = {
@@ -174,12 +175,12 @@ static struct scsi_host_template sil_sht
.queuecommand = ata_scsi_queuecmd,
.can_queue = ATA_DEF_QUEUE,
.this_id = ATA_SHT_THIS_ID,
- .sg_tablesize = LIBATA_MAX_PRD,
+ .sg_tablesize = 120, /* max 15 kiB sectors ? */
.cmd_per_lun = ATA_SHT_CMD_PER_LUN,
.emulated = ATA_SHT_EMULATED,
- .use_clustering = ATA_SHT_USE_CLUSTERING,
+ .use_clustering = 1,
.proc_name = DRV_NAME,
- .dma_boundary = ATA_DMA_BOUNDARY,
+ .dma_boundary = 0x1fff,
.slave_configure = ata_scsi_slave_config,
.slave_destroy = ata_scsi_slave_destroy,
.bios_param = ata_std_bios_param,
@@ -187,6 +188,7 @@ static struct scsi_host_template sil_sht

static const struct ata_port_operations sil_ops = {
.port_disable = ata_port_disable,
+ .fill_sg = sil_fill_sg,
.dev_config = sil_dev_config,
.tf_load = ata_tf_load,
.tf_read = ata_tf_read,
@@ -278,9 +280,9 @@ MODULE_LICENSE("GPL");
MODULE_DEVICE_TABLE(pci, sil_pci_tbl);
MODULE_VERSION(DRV_VERSION);

-static int slow_down = 0;
-module_param(slow_down, int, 0444);
-MODULE_PARM_DESC(slow_down, "Sledgehammer used to work around random
problems, by limiting commands to 15 sectors (0=off, 1=on)");
+static int mod15_quirk = 0;
+module_param(mod15_quirk, int, 0444);
+MODULE_PARM_DESC(mod15_quirk, "Some disks from Seagate need a mod15
workaround.");


static unsigned char sil_get_device_cache_line(struct pci_dev *pdev)
@@ -534,6 +536,44 @@ static void sil_thaw(struct ata_port *ap
writel(tmp, mmio_base + SIL_SYSCFG);
}

+static void sil_fill_sg(struct ata_queued_cmd *qc)
+{
+ struct ata_port *ap = qc->ap;
+ u32 addr, len;
+ unsigned int idx;
+
+ ata_fill_sg(qc);
+
+ /* check if we need the MOD15 workaround */
+ if (!(qc->dev->quirk & SIL_FLAG_MOD15WRITE))
+ return;
+
+ if (unlikely(qc->n_elem < 1))
+ return;
+
+ /* hardware S/G list may be longer (or shorter) than number of
+ * PCI-mapped S/G entries (qc->n_elem), due to splitting
+ * in ata_fill_sg(). Start at zero, and skip to end
+ * of list, if we're not already there.
+ */
+ idx = 0;
+ while ((le32_to_cpu(ap->prd[idx].flags_len) & ATA_PRD_EOT) == 0)
+ idx++;
+
+ /* Errata workaround: if last segment is exactly 8K, split
+ * into 7.5K and 512b pieces.
+ */
+ len = le32_to_cpu(ap->prd[idx].flags_len) & 0xffff;
+ if (len == 8192) {
+ addr = le32_to_cpu(ap->prd[idx].addr);
+ ap->prd[idx].flags_len = cpu_to_le32(15 * 512);
+
+ idx++;
+ ap->prd[idx].addr = cpu_to_le32(addr + (15 * 512));
+ ap->prd[idx].flags_len = cpu_to_le32(512 | ATA_PRD_EOT);
+ }
+}
+
/**
* sil_dev_config - Apply device/host-specific errata fixups
* @dev: Device to be examined
@@ -577,14 +617,14 @@ static void sil_dev_config(struct ata_de
break;
}

- /* limit requests to 15 sectors */
- if (slow_down ||
+ /* mod15 bug */
+ if (mod15_quirk ||
((ap->flags & SIL_FLAG_MOD15WRITE) &&
(quirks & SIL_QUIRK_MOD15WRITE))) {
if (print_info)
ata_dev_printk(dev, KERN_INFO, "applying Seagate "
"errata fix (mod15write workaround)\n");
- dev->max_sectors = 15;
+ dev->quirk |= SIL_FLAG_MOD15WRITE;
return;
}

Index: linux-2.6.23-rc9/include/linux/libata.h
===================================================================
--- linux-2.6.23-rc9.orig/include/linux/libata.h 2007-10-02 17:21:28.000000000
+0200
+++ linux-2.6.23-rc9/include/linux/libata.h 2007-10-11 10:53:31.000000000
+0200
@@ -471,6 +471,9 @@ struct ata_device {
/* error history */
struct ata_ering ering;
int spdn_cnt;
+
+ /* driver specific flags */
+ unsigned int quirk;
};

/* Offset into struct ata_device. Fields above it are maintained
@@ -641,6 +644,8 @@ struct ata_port_operations {

void (*bmdma_stop) (struct ata_queued_cmd *qc);
u8 (*bmdma_status) (struct ata_port *ap);
+
+ void (*fill_sg) (struct ata_queued_cmd *qc);
};

struct ata_port_info {
@@ -789,6 +794,7 @@ extern void ata_data_xfer_noirq(struct a
unsigned int buflen, int write_data);
extern void ata_dumb_qc_prep(struct ata_queued_cmd *qc);
extern void ata_qc_prep(struct ata_queued_cmd *qc);
+extern void ata_fill_sg(struct ata_queued_cmd *qc);
extern void ata_noop_qc_prep(struct ata_queued_cmd *qc);
extern unsigned int ata_qc_issue_prot(struct ata_queued_cmd *qc);
extern void ata_sg_init_one(struct ata_queued_cmd *qc, void *buf,

--
Bernd Schubert
Q-Leap Networks GmbH
-
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