mmc: dw_mmc: set the supported max/min frequency

Both f_max and f_min will be informed for core layer to request
valid clock rate. But current setting from 'host->bus_hz' may
not represent the max/min frequency properly. Even if host can
actually support high speed than bus_hz, core layer will not
request clock rate over bus_hz. Basically, f_max/f_min can be set
with the values according to spec. And then host will make its best
effort to meet the rate.

Signed-off-by: Seungwon Jeon <tgih.jun@samsung.com>
Tested-by: Alim Akhtar <alim.akhtar@samsung.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

2 files changed, 16 insertions, 2 deletions

diff --git a/Documentation/devicetree/bindings/mmc/synopsis-dw-mshc.txt b/Documentation/devicetree/bindings/mmc/synopsis-dw-mshc.txt
index ae5f8e89e845..fdbf6863b00b 100644
--- a/Documentation/devicetree/bindings/mmc/synopsis-dw-mshc.txt
+++ b/Documentation/devicetree/bindings/mmc/synopsis-dw-mshc.txt
@@ -52,6 +52,9 @@ Optional properties:
   is specified and the ciu clock is specified then we'll try to set the ciu
   clock to this at probe time.
 
+* clock-freq-min-max: Minimum and Maximum clock frequency for card output
+  clock(cclk_out). If it's not specified, max is 200MHZ and min is 400KHz by default.
+
 * num-slots: specifies the number of slots supported by the controller.
   The number of physical slots actually used could be equal or less than the
   value specified by num-slots. If this property is not specified, the value
@@ -97,6 +100,7 @@ board specific portions as listed below.
 
         dwmmc0@12200000 {
                 clock-frequency = <400000000>;
+                clock-freq-min-max = <400000 200000000>;
                 num-slots = <1>;
                 supports-highspeed;
                 caps2-mmc-hs200-1_8v;
diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
index cca9aa6b11c5..50da6e330a15 100644
--- a/drivers/mmc/host/dw_mmc.c
+++ b/drivers/mmc/host/dw_mmc.c
@@ -50,6 +50,9 @@
 #define DW_MCI_RECV_STATUS      2
 #define DW_MCI_DMA_THRESHOLD    16
 
+#define DW_MCI_FREQ_MAX 200000000       /* unit: HZ */
+#define DW_MCI_FREQ_MIN 400000          /* unit: HZ */
+
 #ifdef CONFIG_MMC_DW_IDMAC
 #define IDMAC_INT_CLR           (SDMMC_IDMAC_INT_AI | SDMMC_IDMAC_INT_NI | \
                                  SDMMC_IDMAC_INT_CES | SDMMC_IDMAC_INT_DU | \
@@ -1936,6 +1939,7 @@ static int dw_mci_init_slot(struct dw_mci *host, unsigned int id)
         struct dw_mci_slot *slot;
         const struct dw_mci_drv_data *drv_data = host->drv_data;
         int ctrl_id, ret;
+        u32 freq[2];
         u8 bus_width;
 
         mmc = mmc_alloc_host(sizeof(struct dw_mci_slot), host->dev);
@@ -1951,8 +1955,14 @@ static int dw_mci_init_slot(struct dw_mci *host, unsigned int id)
         slot->quirks = dw_mci_of_get_slot_quirks(host->dev, slot->id);
 
         mmc->ops = &dw_mci_ops;
-        mmc->f_min = DIV_ROUND_UP(host->bus_hz, 510);
-        mmc->f_max = host->bus_hz;
+        if (of_property_read_u32_array(host->dev->of_node,
+                                       "clock-freq-min-max", freq, 2)) {
+                mmc->f_min = DW_MCI_FREQ_MIN;
+                mmc->f_max = DW_MCI_FREQ_MAX;
+        } else {
+                mmc->f_min = freq[0];
+                mmc->f_max = freq[1];
+        }
 
         if (host->pdata->get_ocr)
                 mmc->ocr_avail = host->pdata->get_ocr(id);