[ARM] pxa: cpufreq-pxa2xx: sdram_rows detection support

This patch implements Eric Miao's idea to detect the correct value of
sdram_rows by inspecting the MDCNFG register settings.
It is only tested on two pxa27x devices with 64MB RAM (magician and
hx4700) so far.
Signed-off-by: Philipp Zabel <philipp.zabel@gmail.com>
Signed-off-by: Eric Miao <eric.miao@marvell.com>

arch/arm/mach-pxa/cpufreq-pxa2xx.c

@@ -64,7 +64,7 @@ typedef struct {
 
 /* Define the refresh period in mSec for the SDRAM and the number of rows */
 #define SDRAM_TREF	64	/* standard 64ms SDRAM */
-#define SDRAM_ROWS	4096	/* 64MB=8192 32MB=4096 */
+static unsigned int sdram_rows;
 
 #define CCLKCFG_TURBO		0x1
 #define CCLKCFG_FCS		0x2
@@ -73,6 +73,9 @@ typedef struct {
 #define MDREFR_DB2_MASK		(MDREFR_K2DB2 | MDREFR_K1DB2)
 #define MDREFR_DRI_MASK		0xFFF
 
+#define MDCNFG_DRAC2(mdcnfg) (((mdcnfg) >> 21) & 0x3)
+#define MDCNFG_DRAC0(mdcnfg) (((mdcnfg) >> 5) & 0x3)
+
 /*
  * PXA255 definitions
  */
@@ -192,14 +195,28 @@ static void pxa27x_guess_max_freq(void)
 	}
 }
 
+static void init_sdram_rows(void)
+{
+	uint32_t mdcnfg = MDCNFG;
+	unsigned int drac2 = 0, drac0 = 0;
+
+	if (mdcnfg & (MDCNFG_DE2 | MDCNFG_DE3))
+		drac2 = MDCNFG_DRAC2(mdcnfg);
+
+	if (mdcnfg & (MDCNFG_DE0 | MDCNFG_DE1))
+		drac0 = MDCNFG_DRAC0(mdcnfg);
+
+	sdram_rows = 1 << (11 + max(drac0, drac2));
+}
+
 static u32 mdrefr_dri(unsigned int freq)
 {
 	u32 dri = 0;
 
 	if (cpu_is_pxa25x())
-		dri = ((freq * SDRAM_TREF) / (SDRAM_ROWS * 32));
+		dri = ((freq * SDRAM_TREF) / (sdram_rows * 32));
 	if (cpu_is_pxa27x())
-		dri = ((freq * SDRAM_TREF) / (SDRAM_ROWS - 31)) / 32;
+		dri = ((freq * SDRAM_TREF) / (sdram_rows - 31)) / 32;
 	return dri;
 }
 
@@ -334,6 +351,8 @@ static __init int pxa_cpufreq_init(struct cpufreq_policy *policy)
 	if (cpu_is_pxa27x())
 		pxa27x_guess_max_freq();
 
+	init_sdram_rows();
+
 	/* set default policy and cpuinfo */
 	policy->cpuinfo.transition_latency = 1000; /* FIXME: 1 ms, assumed */
 	policy->cur = get_clk_frequency_khz(0);	   /* current freq */

arch/arm/mach-pxa/include/mach/pxa2xx-regs.h

@@ -49,6 +49,11 @@
 #define MECR_NOS	(1 << 0)	/* Number Of Sockets: 0 -> 1 sock, 1 -> 2 sock */
 #define MECR_CIT	(1 << 1)	/* Card Is There: 0 -> no card, 1 -> card inserted */
 
+#define MDCNFG_DE0	(1 << 0)	/* SDRAM Bank 0 Enable */
+#define MDCNFG_DE1	(1 << 1)	/* SDRAM Bank 1 Enable */
+#define MDCNFG_DE2	(1 << 16)	/* SDRAM Bank 2 Enable */
+#define MDCNFG_DE3	(1 << 17)	/* SDRAM Bank 3 Enable */
+
 #define MDREFR_K0DB4	(1 << 29)	/* SDCLK0 Divide by 4 Control/Status */
 #define MDREFR_K2FREE	(1 << 25)	/* SDRAM Free-Running Control */
 #define MDREFR_K1FREE	(1 << 24)	/* SDRAM Free-Running Control */