mmc: sdhci-esdhc-imx: add delay line setting support

The DLL(Delay Line) is newly added to assist in sampling read data.
The DLL provides the ability to programmatically select a quantized
delay (in fractions of the clock period) regardless of on-chip variations
such as process, voltage and temperature (PVT).

This patch adds a user interface to set slave delay line via device tree.
It's usually used in high speed mode like mmc DDR mode when the signal
quality is not good caused by board design, e.g. the signal path is too
long.  User can manually set delay line to find a suitable data sampling
window for card to work properly.

Signed-off-by: Dong Aisheng <b29396@freescale.com>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Chris Ball <cjb@laptop.org>

diff --git a/Documentation/devicetree/bindings/mmc/fsl-imx-esdhc.txt b/Documentation/devicetree/bindings/mmc/fsl-imx-esdhc.txt
index 1dd622546d06b711bf262358b387b4bb9af3f68a..9046ba06c47ab63570f99769455dcfeeea020e10 100644 (file)
--- a/Documentation/devicetree/bindings/mmc/fsl-imx-esdhc.txt
+++ b/Documentation/devicetree/bindings/mmc/fsl-imx-esdhc.txt
@@ -12,6 +12,11 @@ Required properties:
 Optional properties:
 - fsl,cd-controller : Indicate to use controller internal card detection
 - fsl,wp-controller : Indicate to use controller internal write protection
+- fsl,delay-line : Specify the number of delay cells for override mode.
+  This is used to set the clock delay for DLL(Delay Line) on override mode
+  to select a proper data sampling window in case the clock quality is not good
+  due to signal path is too long on the board. Please refer to eSDHC/uSDHC
+  chapter, DLL (Delay Line) section in RM for details.
 
 Examples:
 

diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci-esdhc-imx.c
index 915fa68e5122ee5612c2bd27b67029226aebc6af..260a81fde18da2cc5d9bced3bfdce81ce5e6d729 100644 (file)
--- a/drivers/mmc/host/sdhci-esdhc-imx.c
+++ b/drivers/mmc/host/sdhci-esdhc-imx.c
@@ -46,6 +46,11 @@
 /* Bits 3 and 6 are not SDHCI standard definitions */
 #define  ESDHC_MIX_CTRL_SDHCI_MASK     0xb7
 
+/* dll control register */
+#define ESDHC_DLL_CTRL                 0x60
+#define ESDHC_DLL_OVERRIDE_VAL_SHIFT   9
+#define ESDHC_DLL_OVERRIDE_EN_SHIFT    8
+
 /* tune control register */
 #define ESDHC_TUNE_CTRL_STATUS         0x68
 #define  ESDHC_TUNE_CTRL_STEP          1
@@ -817,6 +822,7 @@ static int esdhc_set_uhs_signaling(struct sdhci_host *host, unsigned int uhs)
 {
        struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
        struct pltfm_imx_data *imx_data = pltfm_host->priv;
+       struct esdhc_platform_data *boarddata = &imx_data->boarddata;
 
        switch (uhs) {
        case MMC_TIMING_UHS_SDR12:
@@ -837,6 +843,15 @@ static int esdhc_set_uhs_signaling(struct sdhci_host *host, unsigned int uhs)
                                ESDHC_MIX_CTRL_DDREN,
                                host->ioaddr + ESDHC_MIX_CTRL);
                imx_data->is_ddr = 1;
+               if (boarddata->delay_line) {
+                       u32 v;
+                       v = boarddata->delay_line <<
+                               ESDHC_DLL_OVERRIDE_VAL_SHIFT |
+                               (1 << ESDHC_DLL_OVERRIDE_EN_SHIFT);
+                       if (is_imx53_esdhc(imx_data))
+                               v <<= 1;
+                       writel(v, host->ioaddr + ESDHC_DLL_CTRL);
+               }
                break;
        }
 
@@ -901,6 +916,9 @@ sdhci_esdhc_imx_probe_dt(struct platform_device *pdev,
        else
                boarddata->support_vsel = true;
 
+       if (of_property_read_u32(np, "fsl,delay-line", &boarddata->delay_line))
+               boarddata->delay_line = 0;
+
        return 0;
 }
 #else

diff --git a/include/linux/platform_data/mmc-esdhc-imx.h b/include/linux/platform_data/mmc-esdhc-imx.h
index a0f5a8f9b3bc08b3d4c17930806cfb82c9c484c6..75f70f6ac13778f448a03de3136d32a0ef638b65 100644 (file)
--- a/include/linux/platform_data/mmc-esdhc-imx.h
+++ b/include/linux/platform_data/mmc-esdhc-imx.h
@@ -45,5 +45,6 @@ struct esdhc_platform_data {
        int max_bus_width;
        unsigned int f_max;
        bool support_vsel;
+       unsigned int delay_line;
 };
 #endif /* __ASM_ARCH_IMX_ESDHC_H */