SM501: Clock updates and checks

Ensure that the M1XCLK and MCLK are sourced from the same PLL (and refuse to
bind the driver if they are not).

Update the PCI to safe initialisation values, as 72MHz is the maximum clock
for 33MHz PCI bus mastering.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 31 insertions, 2 deletions

diff --git a/drivers/mfd/sm501.c b/drivers/mfd/sm501.c
index 3a0ecfc404e9..e14d70e07418 100644
--- a/drivers/mfd/sm501.c
+++ b/drivers/mfd/sm501.c
@@ -855,6 +855,24 @@ static void sm501_init_regs(struct sm501_devdata *sm,
 		dev_info(sm->dev, "setting MCLK to %ld\n", init->mclk);
 		sm501_set_clock(sm->dev, SM501_CLOCK_MCLK, init->mclk);
 	}
+
+}
+
+/* Check the PLL sources for the M1CLK and M1XCLK
+ *
+ * If the M1CLK and M1XCLKs are not sourced from the same PLL, then
+ * there is a risk (see errata AB-5) that the SM501 will cease proper
+ * function. If this happens, then it is likely the SM501 will
+ * hang the system.
+*/
+
+static int sm501_check_clocks(struct sm501_devdata *sm)
+{
+	unsigned long pwrmode = readl(sm->regs + SM501_CURRENT_CLOCK);
+	unsigned long msrc = (pwrmode & SM501_POWERMODE_M_SRC);
+	unsigned long m1src = (pwrmode & SM501_POWERMODE_M1_SRC);
+
+	return ((msrc == 0 && m1src != 0) || (msrc != 0 && m1src == 0));
 }
 
 static unsigned int sm501_mem_local[] = {
@@ -911,6 +929,13 @@ static int sm501_init_dev(struct sm501_devdata *sm)
 		}
 	}
 
+	ret = sm501_check_clocks(sm);
+	if (ret) {
+		dev_err(sm->dev, "M1X and M clocks sourced from different "
+					"PLLs\n");
+		return -EINVAL;
+	}
+
 	/* always create a framebuffer */
 	sm501_register_display(sm, &mem_avail);
 
@@ -1048,8 +1073,12 @@ static struct sm501_initdata sm501_pci_initdata = {
 	},
 
 	.devices	= SM501_USE_ALL,
-	.mclk		= 100 * MHZ,
-	.m1xclk		= 160 * MHZ,
+
+	/* Errata AB-3 says that 72MHz is the fastest available
+	 * for 33MHZ PCI with proper bus-mastering operation */
+
+	.mclk		= 72 * MHZ,
+	.m1xclk		= 144 * MHZ,
 };
 
 static struct sm501_platdata_fbsub sm501_pdata_fbsub = {