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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>
This commit is contained in:
Dong Aisheng 2013-10-18 19:48:47 +08:00 committed by Chris Ball
parent de5bdbffd8
commit 602519b2bd
3 changed files with 24 additions and 0 deletions
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5
Documentation/devicetree/bindings/mmc/fsl-imx-esdhc.txt
View File

@ -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:

18
drivers/mmc/host/sdhci-esdhc-imx.c
View File

@ -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

1
include/linux/platform_data/mmc-esdhc-imx.h
View File

@ -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 */