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@xxxxxxxxxxx>
Tested-by: Alim Akhtar <alim.akhtar@xxxxxxxxxxx>
---
.../devicetree/bindings/mmc/synopsis-dw-mshc.txt | 4 ++++
drivers/mmc/host/dw_mmc.c | 14 ++++++++++++--
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 ae5f8e8..fdbf686 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 7c7cfa2..29deeba 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);
--
1.7.0.4
--
To unsubscribe from this list: send the line "unsubscribe linux-mmc" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
