[PATCH 1/2] sunxi: h616: dram: Rework size detection

[Jernej Skrabec <jernej.skrabec@gmail.com>]

Since there is quite a few possible DRAM configurations in terms of bus
width, rank and rows and columns count, size detection algorithm must be
very careful not to test combination which would be bigger than H616 is
actually capable of handling.

Ideally, we should always detect memory aliasing, even for 4 GB memory
size, which is the maximum amount of memory that H616 is capable of
handling. For this reason, we have to configure minimum amount of
supported rows when testing for columns and vice versa. This way test
code will never step out of 4 GB boundary.

While at it, check for 17 rows maximum. This aligns code with BSP DRAM
driver. There is probably no such configuration which would make sense
with 4 GB memory.

Signed-off-by: Jernej Skrabec <jernej.skrabec@gmail.com>
---
 arch/arm/mach-sunxi/dram_sun50i_h616.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/arch/arm/mach-sunxi/dram_sun50i_h616.c b/arch/arm/mach-sunxi/dram_sun50i_h616.c
index b3554cc64bf5..6f84e59e39cd 100644
--- a/arch/arm/mach-sunxi/dram_sun50i_h616.c
+++ b/arch/arm/mach-sunxi/dram_sun50i_h616.c
@@ -1363,7 +1363,7 @@ static void mctl_auto_detect_rank_width(const struct dram_para *para,
 static void mctl_auto_detect_dram_size(const struct dram_para *para,
 				       struct dram_config *config)
 {
-	unsigned int shift;
+	unsigned int shift, cols, rows;
 
 	/* max. config for columns, but not rows */
 	config->cols = 11;
@@ -1373,23 +1373,27 @@ static void mctl_auto_detect_dram_size(const struct dram_para *para,
 	shift = config->bus_full_width + 1;
 
 	/* detect column address bits */
-	for (config->cols = 8; config->cols < 11; config->cols++) {
-		if (mctl_mem_matches(1ULL << (config->cols + shift)))
+	for (cols = 8; cols < 11; cols++) {
+		if (mctl_mem_matches(1ULL << (cols + shift)))
 			break;
 	}
-	debug("detected %u columns\n", config->cols);
+	debug("detected %u columns\n", cols);
 
 	/* reconfigure to make sure that all active rows are accessible */
-	config->rows = 18;
+	config->cols = 8;
+	config->rows = 17;
 	mctl_core_init(para, config);
 
 	/* detect row address bits */
 	shift = config->bus_full_width + 4 + config->cols;
-	for (config->rows = 13; config->rows < 18; config->rows++) {
-		if (mctl_mem_matches(1ULL << (config->rows + shift)))
+	for (rows = 13; rows < 17; rows++) {
+		if (mctl_mem_matches(1ULL << (rows + shift)))
 			break;
 	}
-	debug("detected %u rows\n", config->rows);
+	debug("detected %u rows\n", rows);
+
+	config->cols = cols;
+	config->rows = rows;
 }
 
 static unsigned long mctl_calc_size(const struct dram_config *config)
-- 
2.48.1