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SubjectRe: [PATCH v2 3/8] mmc: sdhci-st: Add delay management functions for top registers (eMMC).

On 02/26/2015 02:10 PM, Peter Griffin wrote:
> Due to the tight timing constriants in some UHS modes, it is required to have
s/constriant/constraints/
> some delay management in the design. Two types of delay management are supported
> in the HW: -
>
> 1) Static delay management
> 2) Dynamic delay management
>
> NB: The delay management is only there when eMMC interface is selected.
>
> 1: Static delay management: is used to provide PVT dependent static delay on the
> clock/data lines to manage setup/hold requirements of the interface. The maximum
> delay possible is 3.25ns. These delays are PVT dependent, and thus delay values
> applied are not accurate and vary across provcess voltage and temperature range.
> Due to this these delays must not be used on the very time critical paths.
>
> 2. Dynamic delay locked loop (DLL): is used to provide dynamic delay management.
> The advantage of DLL is that it provides accurate & PVT indepedent delay.
>
> The DLL is used to provide delay on the loopback clock on "Read Path" to capture
> read data reliably. On TX path the clock on which output data is transmitted is
> delayed, resulting in delay of TX data.
>
> Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
> Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
> ---
> drivers/mmc/host/sdhci-st.c | 58 +++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 58 insertions(+)
>
> diff --git a/drivers/mmc/host/sdhci-st.c b/drivers/mmc/host/sdhci-st.c
> index 0101ae9..3443cc0 100644
> --- a/drivers/mmc/host/sdhci-st.c
> +++ b/drivers/mmc/host/sdhci-st.c
> @@ -122,6 +122,64 @@ struct st_mmc_platform_data {
> ST_TOP_MMC_DLY_CTRL_ATUNE_NOT_CFG_DLY | \
> ST_TOP_MMC_START_DLL_LOCK)
>
> +/*
> + * For clock speeds greater than 90MHz, we need to check that the
> + * DLL procedure has finished before switching to ultra-speed modes.
> + */
> +#define CLK_TO_CHECK_DLL_LOCK 90000000
> +
> +static inline void st_mmcss_set_static_delay(void __iomem *ioaddr)
> +{
> + if (ioaddr) {
Maybe you could do:
if (!ioaddr)
return;

writel_relaxed....
> + writel_relaxed(0x0, ioaddr + ST_TOP_MMC_DLY_CTRL);
> + writel_relaxed(ST_TOP_MMC_DLY_MAX,
> + ioaddr + ST_TOP_MMC_TX_CLK_DLY);
> + }
> +}
> +
> +static inline void st_mmcss_set_dll(void __iomem *ioaddr)
> +{
> + if (ioaddr) {
Ditto


> + writel_relaxed(ST_TOP_MMC_DYN_DLY_CONF,
> + ioaddr + ST_TOP_MMC_DLY_CTRL);
> + writel_relaxed(ST_TOP_MMC_TX_DLL_STEP_DLY_VALID,
> + ioaddr + ST_TOP_MMC_TX_DLL_STEP_DLY);
> + }
> +}
> +
> +static int st_mmcss_lock_dll(void __iomem *ioaddr)
> +{
> + unsigned long curr, value;
> + unsigned long finish = jiffies + HZ;
> +
> + /* Checks if the DLL procedure is finished */
> + do {
> + curr = jiffies;
> + value = readl(ioaddr + ST_MMC_STATUS_R);
> + if (value & 0x1)
> + return 0;
> +
> + cpu_relax();
> + } while (!time_after_eq(curr, finish));
> +
> + return -EBUSY;
> +}
> +
> +static int sdhci_st_set_dll_for_clock(struct sdhci_host *host)
> +{
> + int ret = 0;
> + struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> + struct st_mmc_platform_data *pdata = pltfm_host->priv;
> +
> + if (host->clock > CLK_TO_CHECK_DLL_LOCK) {
> + st_mmcss_set_dll(pdata->top_ioaddr);
> + ret = st_mmcss_lock_dll(host->ioaddr);
> + }
> +
> + return ret;
> +}
> +
> +
> static u32 sdhci_st_readl(struct sdhci_host *host, int reg)
> {
> u32 ret;



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