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Subject[PATCH 7/7] edac: mpc85xx add dram scrubbing support
From: Peter Tyser <ptyser@xes-inc.com>

Add support to scrub DRAM using the e752x integrated memory scrubbing
engine. The e7320/7520/e7525 chipsets support scrubbing at one rate
while the i3100 chipset supports a normal and fast rate.

A similar patch was originally sent back in 2008:
http://sourceforge.net/mailarchive/forum.php?thread_name=1204835866.25206.70.camel@localhost.localdomain&forum_name=bluesmoke-devel

This version has the following updates:
- Use 16-bit PCI config cycles to access MCHSCRB register
e7320/7520/e7525 docs say register is 16bits wide, i3100 says 8. I
tested 16bits on the i3100 to be safe.
- Recalcuate and round actual scrub rates

The changes have been tested on an i3100-based board.

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
Signed-off-by: Doug Thompson <dougthompson@xmission.com>
---
drivers/edac/e752x_edac.c | 107 +++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 107 insertions(+), 0 deletions(-)
Index: linux-2.6.33-rc4/drivers/edac/e752x_edac.c
===================================================================
--- linux-2.6.33-rc4.orig/drivers/edac/e752x_edac.c 2010-01-12 23:26:13.000000000 -0700
+++ linux-2.6.33-rc4/drivers/edac/e752x_edac.c 2010-01-13 00:02:15.000000000 -0700
@@ -75,6 +75,14 @@ static struct edac_pci_ctl_info *e752x_p
#define E752X_NR_CSROWS 8 /* number of csrows */

/* E752X register addresses - device 0 function 0 */
+#define E752X_MCHSCRB 0x52 /* Memory Scrub register (16b) */
+ /*
+ * 6:5 Scrub Completion Count
+ * 3:2 Scrub Rate (i3100 only)
+ * 01=fast 10=normal
+ * 1:0 Scrub Mode enable
+ * 00=off 10=on
+ */
#define E752X_DRB 0x60 /* DRAM row boundary register (8b) */
#define E752X_DRA 0x70 /* DRAM row attribute register (8b) */
/*
@@ -240,6 +248,41 @@ static const struct e752x_dev_info e752x
.ctl_name = "3100"},
};

+/* Valid scrub rates for the e752x/3100 hardware memory scrubber. We
+ * map the scrubbing bandwidth to a hardware register value. The 'set'
+ * operation finds the 'matching or higher value'. Note that scrubbing
+ * on the e752x can only be enabled/disabled. The 3100 supports
+ * a normal and fast mode.
+ */
+
+#define SDRATE_EOT 0xFFFFFFFF
+
+struct scrubrate {
+ u32 bandwidth; /* bandwidth consumed by scrubbing in bytes/sec */
+ u16 scrubval; /* register value for scrub rate */
+};
+
+/* Rate below assumes same performance as i3100 using PC3200 DDR2 in
+ * normal mode. e752x bridges don't support choosing normal or fast mode,
+ * so the scrubbing bandwidth value isn't all that important - scrubbing is
+ * either on or off.
+ */
+static const struct scrubrate scrubrates_e752x[] = {
+ {0, 0x00}, /* Scrubbing Off */
+ {500000, 0x02}, /* Scrubbing On */
+ {SDRATE_EOT, 0x00} /* End of Table */
+};
+
+/* Fast mode: 2 GByte PC3200 DDR2 scrubbed in 33s = 63161283 bytes/s
+ * Normal mode: 125 (32000 / 256) times slower than fast mode.
+ */
+static const struct scrubrate scrubrates_i3100[] = {
+ {0, 0x00}, /* Scrubbing Off */
+ {500000, 0x0a}, /* Normal mode - 32k clocks */
+ {62500000, 0x06}, /* Fast mode - 256 clocks */
+ {SDRATE_EOT, 0x00} /* End of Table */
+};
+
static unsigned long ctl_page_to_phys(struct mem_ctl_info *mci,
unsigned long page)
{
@@ -915,6 +958,68 @@ static void e752x_check(struct mem_ctl_i
e752x_process_error_info(mci, &info, 1);
}

+/* Program byte/sec bandwidth scrub rate to hardware */
+static int set_sdram_scrub_rate(struct mem_ctl_info *mci, u32 *new_bw)
+{
+ const struct scrubrate *scrubrates;
+ struct e752x_pvt *pvt = (struct e752x_pvt *) mci->pvt_info;
+ struct pci_dev *pdev = pvt->dev_d0f0;
+ int i;
+
+ if (pvt->dev_info->ctl_dev == PCI_DEVICE_ID_INTEL_3100_0)
+ scrubrates = scrubrates_i3100;
+ else
+ scrubrates = scrubrates_e752x;
+
+ /* Translate the desired scrub rate to a e752x/3100 register value.
+ * Search for the bandwidth that is equal or greater than the
+ * desired rate and program the cooresponding register value.
+ */
+ for (i = 0; scrubrates[i].bandwidth != SDRATE_EOT; i++)
+ if (scrubrates[i].bandwidth >= *new_bw)
+ break;
+
+ if (scrubrates[i].bandwidth == SDRATE_EOT)
+ return -1;
+
+ pci_write_config_word(pdev, E752X_MCHSCRB, scrubrates[i].scrubval);
+
+ return 0;
+}
+
+/* Convert current scrub rate value into byte/sec bandwidth */
+static int get_sdram_scrub_rate(struct mem_ctl_info *mci, u32 *bw)
+{
+ const struct scrubrate *scrubrates;
+ struct e752x_pvt *pvt = (struct e752x_pvt *) mci->pvt_info;
+ struct pci_dev *pdev = pvt->dev_d0f0;
+ u16 scrubval;
+ int i;
+
+ if (pvt->dev_info->ctl_dev == PCI_DEVICE_ID_INTEL_3100_0)
+ scrubrates = scrubrates_i3100;
+ else
+ scrubrates = scrubrates_e752x;
+
+ /* Find the bandwidth matching the memory scrubber configuration */
+ pci_read_config_word(pdev, E752X_MCHSCRB, &scrubval);
+ scrubval = scrubval & 0x0f;
+
+ for (i = 0; scrubrates[i].bandwidth != SDRATE_EOT; i++)
+ if (scrubrates[i].scrubval == scrubval)
+ break;
+
+ if (scrubrates[i].bandwidth == SDRATE_EOT) {
+ e752x_printk(KERN_WARNING,
+ "Invalid sdram scrub control value: 0x%x\n", scrubval);
+ return -1;
+ }
+
+ *bw = scrubrates[i].bandwidth;
+
+ return 0;
+}
+
/* Return 1 if dual channel mode is active. Else return 0. */
static inline int dual_channel_active(u16 ddrcsr)
{
@@ -1181,6 +1286,8 @@ static int e752x_probe1(struct pci_dev *
mci->dev_name = pci_name(pdev);
mci->edac_check = e752x_check;
mci->ctl_page_to_phys = ctl_page_to_phys;
+ mci->set_sdram_scrub_rate = set_sdram_scrub_rate;
+ mci->get_sdram_scrub_rate = get_sdram_scrub_rate;

/* set the map type. 1 = normal, 0 = reversed
* Must be set before e752x_init_csrows in case csrow mapping

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