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authorStefan Roese <sr@denx.de>2009-10-19 14:06:23 +0200
committerStefan Roese <sr@denx.de>2009-10-23 16:04:36 +0200
commit5e47f9535f53fd4cc05f32fb6166870f976fbb4e (patch)
tree68b7e4f2a7167fac1d056de8bcf0b9d5fb4769eb /cpu/ppc4xx
parent92b8964bed0d1b779d9e26be4e16755b5c635415 (diff)
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ppc4xx: Add function to check and dynamically change PCI sync clock
PPC440EP(x)/PPC440GR(x): In asynchronous PCI mode, the synchronous PCI clock must meet certain requirements. The following equation describes the relationship that must be maintained between the asynchronous PCI clock and synchronous PCI clock. Select an appropriate PCI:PLB ratio to maintain the relationship: AsyncPCIClk - 1MHz <= SyncPCIclock <= (2 * AsyncPCIClk) - 1MHz This patch now adds a function to check and reconfigure the sync PCI clock to meet this requirement. This is in preparation for some AMCC boards (Sequoia/Rainier and Yosemite/Yellowstone) using this function to not violate the PCI clocking rules. Signed-off-by: Stefan Roese <sr@denx.de>
Diffstat (limited to 'cpu/ppc4xx')
-rw-r--r--cpu/ppc4xx/cpu_init.c69
1 files changed, 69 insertions, 0 deletions
diff --git a/cpu/ppc4xx/cpu_init.c b/cpu/ppc4xx/cpu_init.c
index a00da40..ccd9993 100644
--- a/cpu/ppc4xx/cpu_init.c
+++ b/cpu/ppc4xx/cpu_init.c
@@ -330,3 +330,72 @@ int cpu_init_r (void)
return 0;
}
+
+#if defined(CONFIG_PCI) && \
+ (defined(CONFIG_440EP) || defined(CONFIG_440EPX) || \
+ defined(CONFIG_440GR) || defined(CONFIG_440GRX))
+/*
+ * 440EP(x)/GR(x) PCI async/sync clocking restriction:
+ *
+ * In asynchronous PCI mode, the synchronous PCI clock must meet
+ * certain requirements. The following equation describes the
+ * relationship that must be maintained between the asynchronous PCI
+ * clock and synchronous PCI clock. Select an appropriate PCI:PLB
+ * ratio to maintain the relationship:
+ *
+ * AsyncPCIClk - 1MHz <= SyncPCIclock <= (2 * AsyncPCIClk) - 1MHz
+ */
+static int ppc4xx_pci_sync_clock_ok(u32 sync, u32 async)
+{
+ if (((async - 1000000) > sync) || (sync > ((2 * async) - 1000000)))
+ return 0;
+ else
+ return 1;
+}
+
+int ppc4xx_pci_sync_clock_config(u32 async)
+{
+ sys_info_t sys_info;
+ u32 sync;
+ int div;
+ u32 reg;
+ u32 spcid_val[] = {
+ CPR0_SPCID_SPCIDV0_DIV1, CPR0_SPCID_SPCIDV0_DIV2,
+ CPR0_SPCID_SPCIDV0_DIV3, CPR0_SPCID_SPCIDV0_DIV4 };
+
+ get_sys_info(&sys_info);
+ sync = sys_info.freqPCI;
+
+ /*
+ * First check if the equation above is met
+ */
+ if (!ppc4xx_pci_sync_clock_ok(sync, async)) {
+ /*
+ * Reconfigure PCI sync clock to meet the equation.
+ * Start with highest possible PCI sync frequency
+ * (divider 1).
+ */
+ for (div = 1; div <= 4; div++) {
+ sync = sys_info.freqPLB / div;
+ if (ppc4xx_pci_sync_clock_ok(sync, async))
+ break;
+ }
+
+ if (div <= 4) {
+ mtcpr(CPR0_SPCID, spcid_val[div]);
+
+ mfcpr(CPR0_ICFG, reg);
+ reg |= CPR0_ICFG_RLI_MASK;
+ mtcpr(CPR0_ICFG, reg);
+
+ /* do chip reset */
+ mtspr(SPRN_DBCR0, 0x20000000);
+ } else {
+ /* Impossible to configure the PCI sync clock */
+ return -1;
+ }
+ }
+
+ return 0;
+}
+#endif