Dan Aloni wrote:
Hello,
With the patch below I've managed to stabilize the sata_mv driver
running a Marvell 5081 SATA controller. Prior to these changes it
would cause sporadic memory corruptions right after insmod. I prefer
this driver over Marvell's own driver which have all sorts of weird
bugs.
The patch also increases the maximum possible number of SG entries
per IO to 256 (this large sg_tablesize is a requirement for the
application we are developing at my company, XIV). Notice that it
also zeros-out a reserved field in the SG, I'm not sure how it
affected stability but something did. I've also added the 'volatile'
qualifier to some fields that belong to structs involved with I/O.
Adding 'volatile' is to be avoided. This is simply hiding bugs
elsewhere. volatile is an "atom bomb" that kills quite valid
optimizations, needlessly. Most likely you need to sprinkle rmb(),
wmb(), and/or mb() in the correct locations.
Also, it isn't clear at all from your description precisely which
changes are fixes, and which are cleanups and optimizations. It would
be nice to get each category of changes split into two separate patches.
--- drivers/scsi/sata_mv.c 2006-03-08 11:30:10.000000000 +0200
+++ drivers/scsi/sata_mv.c 2006-03-08 20:59:55.000000000 +0200
@@ -72,9 +72,10 @@
*/
MV_CRQB_Q_SZ = (32 * MV_MAX_Q_DEPTH),
MV_CRPB_Q_SZ = (8 * MV_MAX_Q_DEPTH),
- MV_MAX_SG_CT = 176,
+ MV_MAX_SG_CT = 256,
MV_SG_TBL_SZ = (16 * MV_MAX_SG_CT),
- MV_PORT_PRIV_DMA_SZ = (MV_CRQB_Q_SZ + MV_CRPB_Q_SZ + MV_SG_TBL_SZ),
+ MV_PORT_PRIV_DMA1_SZ = (MV_CRQB_Q_SZ + MV_CRPB_Q_SZ),
+ MV_PORT_PRIV_DMA2_SZ = (MV_SG_TBL_SZ),
MV_PORTS_PER_HC = 4,
/* == (port / MV_PORTS_PER_HC) to determine HC from 0-7 port */
@@ -98,7 +99,7 @@
CRPB_FLAG_STATUS_SHIFT = 8,
- EPRD_FLAG_END_OF_TBL = (1 << 31),
+ EPRD_FLAG_END_OF_TBL = (1 << 15),
/* PCI interface registers */
@@ -257,29 +258,34 @@
chip_608x,
};
+#pragma pack(1)
+
/* Command ReQuest Block: 32B */
struct mv_crqb {
- u32 sg_addr;
- u32 sg_addr_hi;
- u16 ctrl_flags;
+ volatile u32 sg_addr;
+ volatile u32 sg_addr_hi;
+ volatile u16 ctrl_flags;
u16 ata_cmd[11];
};
/* Command ResPonse Block: 8B */
struct mv_crpb {
- u16 id;
- u16 flags;
- u32 tmstmp;
+ volatile u16 id;
+ volatile u16 flags;
+ volatile u32 tmstmp;
};
/* EDMA Physical Region Descriptor (ePRD); A.K.A. SG */
struct mv_sg {
- u32 addr;
- u32 flags_size;
- u32 addr_hi;
- u32 reserved;
+ volatile u32 addr;
+ volatile u16 size;
+ volatile u16 flags;
+ volatile u32 addr_hi;
+ volatile u32 reserved;
};
+#pragma pack(0)
+
struct mv_port_priv {
struct mv_crqb *crqb;
dma_addr_t crqb_dma;
@@ -294,8 +300,8 @@
};
struct mv_port_signal {
- u32 amps;
- u32 pre;
+ volatile u32 amps;
+ volatile u32 pre;
};
see comment on 'volatile', above. We can't add these changes.
struct mv_host_priv;
@@ -365,7 +371,7 @@
.eh_strategy_handler = ata_scsi_error,
.can_queue = MV_USE_Q_DEPTH,
.this_id = ATA_SHT_THIS_ID,
- .sg_tablesize = MV_MAX_SG_CT / 2,
+ .sg_tablesize = MV_MAX_SG_CT,
This is adding a bug.
The IOMMU worst case requires a split for each s/g entry, due to DMA
boundary issues. See mv_fill_sg() or ata_fill_sg().
Thus, the above "/ 2" is required.
.max_sectors = ATA_MAX_SECTORS,
.cmd_per_lun = ATA_SHT_CMD_PER_LUN,
.emulated = ATA_SHT_EMULATED,
@@ -509,10 +515,7 @@
.reset_bus = mv_reset_pci_bus,
};
-/*
- * module options
- */
-static int msi; /* Use PCI msi; either zero (off, default) or non-zero */
+static int msi; /* Use PCI msi; either zero (off, default) or non-zero */
what changed here?
/*
@@ -770,7 +773,8 @@
static inline void mv_priv_free(struct mv_port_priv *pp, struct device *dev)
{
- dma_free_coherent(dev, MV_PORT_PRIV_DMA_SZ, pp->crpb, pp->crpb_dma);
+ dma_free_coherent(dev, MV_PORT_PRIV_DMA1_SZ, pp->crpb, pp->crpb_dma);
+ dma_free_coherent(dev, MV_PORT_PRIV_DMA2_SZ, pp->sg_tbl, pp->sg_tbl_dma);
}
/**
@@ -788,8 +792,8 @@
struct device *dev = ap->host_set->dev;
struct mv_port_priv *pp;
void __iomem *port_mmio = mv_ap_base(ap);
- void *mem;
- dma_addr_t mem_dma;
+ void *mem, *mem2;
+ dma_addr_t mem_dma, mem_dma2;
int rc = -ENOMEM;
pp = kmalloc(sizeof(*pp), GFP_KERNEL);
@@ -797,11 +801,17 @@
goto err_out;
memset(pp, 0, sizeof(*pp));
- mem = dma_alloc_coherent(dev, MV_PORT_PRIV_DMA_SZ, &mem_dma,
+ mem = dma_alloc_coherent(dev, MV_PORT_PRIV_DMA1_SZ, &mem_dma,
GFP_KERNEL);
if (!mem)
goto err_out_pp;
- memset(mem, 0, MV_PORT_PRIV_DMA_SZ);
+ memset(mem, 0, MV_PORT_PRIV_DMA1_SZ);
+
+ mem2 = dma_alloc_coherent(dev, MV_PORT_PRIV_DMA2_SZ, &mem_dma2,
+ GFP_KERNEL);
+ if (!mem2)
+ goto err_out_pp_2;
+ memset(mem2, 0, MV_PORT_PRIV_DMA2_SZ);
rc = ata_pad_alloc(ap, dev);
if (rc)
@@ -820,14 +830,12 @@
*/
pp->crpb = mem;
pp->crpb_dma = mem_dma;
- mem += MV_CRPB_Q_SZ;
- mem_dma += MV_CRPB_Q_SZ;
/* Third item:
* Table of scatter-gather descriptors (ePRD), 16 bytes each
*/
- pp->sg_tbl = mem;
- pp->sg_tbl_dma = mem_dma;
+ pp->sg_tbl = mem2;
+ pp->sg_tbl_dma = mem_dma2;
why two allocations?
why not just fix the [probable] alignment issue?
I also agree with John Stoffel's comments.
Jeff
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