[PATCH v2] mmc: mtk-sd: increase the minimum bus frequency

[Weijie Gao]

With a 48MHz input clock, the lowest bus frequency can be as low as
48000000 / (4 * 4095) = 2930Hz. Such an extremely low frequency will cause
the mmc framework take seconds to finish the initialization.

Limiting the minimum bus frequency to a slightly higher value can solve the
issue without any side effects.

Signed-off-by: Weijie Gao <weijie.gao at mediatek.com>
---
 drivers/mmc/mtk-sd.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/mmc/mtk-sd.c b/drivers/mmc/mtk-sd.c
index 3b9c122..626a4d3 100644
--- a/drivers/mmc/mtk-sd.c
+++ b/drivers/mmc/mtk-sd.c
@@ -232,6 +232,8 @@
 
 #define SCLK_CYCLES_SHIFT		20
 
+#define MIN_BUS_CLK			200000
+
 #define CMD_INTS_MASK	\
 	(MSDC_INT_CMDRDY | MSDC_INT_RSPCRCERR | MSDC_INT_CMDTMO)
 
@@ -1639,6 +1641,9 @@ static int msdc_drv_probe(struct udevice *dev)
 	else
 		cfg->f_min = host->src_clk_freq / (4 * 4095);
 
+	if (cfg->f_min < MIN_BUS_CLK)
+		cfg->f_min = MIN_BUS_CLK;
+
 	cfg->f_max = host->src_clk_freq;
 
 	cfg->b_max = 1024;
-- 
1.9.1