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Date: Wed, 12 Sep 2012 14:51:34 +0530
From: "T Krishnamoorthy, Balaji" <balajitk@...com>
To: "Hebbar, Gururaja" <gururaja.hebbar@...com>
Cc: linux-omap@...r.kernel.org, linux-mmc@...r.kernel.org,
svenkatr@...com, rob.herring@...xeda.com,
linux-kernel@...r.kernel.org, grant.likely@...retlab.ca,
cjb@...top.org, nsekhar@...com, sudhakar.raj@...com
Subject: Re: [PATCH] mmc: omap_hsmmc: Enable HSPE bit for high speed cards
On Tue, Sep 4, 2012 at 6:39 PM, Hebbar, Gururaja <gururaja.hebbar@...com> wrote:
> HSMMC IP on AM33xx need a special setting to handle High-speed cards.
> Other platforms like TI81xx, OMAP4 may need this as-well. This depends
> on the HSMMC IP timing closure done for the high speed cards.
>
> From AM335x TRM (SPRUH73F - 18.3.12 Output Signals Generation)
>
> The MMC/SD/SDIO output signals can be driven on either falling edge or
> rising edge depending on the SD_HCTL[2] HSPE bit. This feature allows
> to reach better timing performance, and thus to increase data transfer
> frequency.
Is this specific to some boards or all board with TI81xx ?
What is the side-effect if not done ?
>
> There are few pre-requisites for enabling the HSPE bit
> - Controller should support High-Speed-Enable Bit and
> - Controller should not be using DDR Mode and
> - Controller should advertise that it supports High Speed in
> capabilities register and
> - MMC/SD clock coming out of controller > 25MHz
>
> Signed-off-by: Hebbar, Gururaja <gururaja.hebbar@...com>
> ---
> :100644 100644 be76a23... ed271fc... M Documentation/devicetree/bindings/mmc/ti-omap-hsmmc.txt
> :100644 100644 eb3e4d5... 00c658b... M arch/arm/plat-omap/include/plat/mmc.h
> :100644 100644 c3e96a2... 0e14834... M drivers/mmc/host/omap_hsmmc.c
> .../devicetree/bindings/mmc/ti-omap-hsmmc.txt | 1 +
> arch/arm/plat-omap/include/plat/mmc.h | 1 +
> drivers/mmc/host/omap_hsmmc.c | 30 +++++++++++++++++++-
> 3 files changed, 31 insertions(+), 1 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/mmc/ti-omap-hsmmc.txt b/Documentation/devicetree/bindings/mmc/ti-omap-hsmmc.txt
> index be76a23..ed271fc 100644
> --- a/Documentation/devicetree/bindings/mmc/ti-omap-hsmmc.txt
> +++ b/Documentation/devicetree/bindings/mmc/ti-omap-hsmmc.txt
> @@ -19,6 +19,7 @@ ti,dual-volt: boolean, supports dual voltage cards
> "supply-name" examples are "vmmc", "vmmc_aux" etc
> ti,non-removable: non-removable slot (like eMMC)
> ti,needs-special-reset: Requires a special softreset sequence
> +ti,needs-special-hs-handling: HSMMC IP needs special setting for handling High Speed
>
> Example:
> mmc1: mmc@...809c000 {
> diff --git a/arch/arm/plat-omap/include/plat/mmc.h b/arch/arm/plat-omap/include/plat/mmc.h
> index eb3e4d5..00c658b 100644
> --- a/arch/arm/plat-omap/include/plat/mmc.h
> +++ b/arch/arm/plat-omap/include/plat/mmc.h
> @@ -127,6 +127,7 @@ struct omap_mmc_platform_data {
> /* we can put the features above into this variable */
> #define HSMMC_HAS_PBIAS (1 << 0)
> #define HSMMC_HAS_UPDATED_RESET (1 << 1)
> +#define HSMMC_HAS_HSPE_SUPPORT (1 << 2)
> unsigned features;
>
> int switch_pin; /* gpio (card detect) */
> diff --git a/drivers/mmc/host/omap_hsmmc.c b/drivers/mmc/host/omap_hsmmc.c
> index c3e96a2..0e14834 100644
> --- a/drivers/mmc/host/omap_hsmmc.c
> +++ b/drivers/mmc/host/omap_hsmmc.c
> @@ -63,6 +63,7 @@
>
> #define VS18 (1 << 26)
> #define VS30 (1 << 25)
> +#define HSS (1 << 21)
> #define SDVS18 (0x5 << 9)
> #define SDVS30 (0x6 << 9)
> #define SDVS33 (0x7 << 9)
> @@ -90,6 +91,7 @@
> #define MSBS (1 << 5)
> #define BCE (1 << 1)
> #define FOUR_BIT (1 << 1)
> +#define HSPE (1 << 2)
> #define DDR (1 << 19)
> #define DW8 (1 << 5)
> #define CC 0x1
> @@ -490,6 +492,7 @@ static void omap_hsmmc_set_clock(struct omap_hsmmc_host *host)
> struct mmc_ios *ios = &host->mmc->ios;
> unsigned long regval;
> unsigned long timeout;
> + unsigned long clkdiv;
>
> dev_vdbg(mmc_dev(host->mmc), "Set clock to %uHz\n", ios->clock);
>
> @@ -497,7 +500,8 @@ static void omap_hsmmc_set_clock(struct omap_hsmmc_host *host)
>
> regval = OMAP_HSMMC_READ(host->base, SYSCTL);
> regval = regval & ~(CLKD_MASK | DTO_MASK);
> - regval = regval | (calc_divisor(host, ios) << 6) | (DTO << 16);
> + clkdiv = calc_divisor(host, ios);
> + regval = regval | (clkdiv << 6) | (DTO << 16);
> OMAP_HSMMC_WRITE(host->base, SYSCTL, regval);
> OMAP_HSMMC_WRITE(host->base, SYSCTL,
> OMAP_HSMMC_READ(host->base, SYSCTL) | ICE);
> @@ -508,6 +512,27 @@ static void omap_hsmmc_set_clock(struct omap_hsmmc_host *host)
> && time_before(jiffies, timeout))
> cpu_relax();
>
> + /*
> + * Enable High-Speed Support
> + * Pre-Requisites
> + * - Controller should support High-Speed-Enable Bit
> + * - Controller should not be using DDR Mode
> + * - Controller should advertise that it supports High Speed
> + * in capabilities register
> + * - MMC/SD clock coming out of controller > 25MHz
> + */
> + if ((mmc_slot(host).features & HSMMC_HAS_HSPE_SUPPORT) &&
> + (ios->timing != MMC_TIMING_UHS_DDR50) &&
> + ((OMAP_HSMMC_READ(host->base, CAPA) & HSS) == HSS)) {
> + regval = OMAP_HSMMC_READ(host->base, HCTL);
> + if (clkdiv && (clk_get_rate(host->fclk)/clkdiv) > 25000000)
I think clkdiv is not needed
clk_get_rate(host->fclk)/clkdiv is same as ios->clock
> + regval |= HSPE;
> + else
> + regval &= ~HSPE;
> +
> + OMAP_HSMMC_WRITE(host->base, HCTL, regval);
> + }
> +
> omap_hsmmc_start_clock(host);
> }
>
> @@ -1701,6 +1726,9 @@ static struct omap_mmc_platform_data *of_get_hsmmc_pdata(struct device *dev)
> if (of_find_property(np, "ti,needs-special-reset", NULL))
> pdata->slots[0].features |= HSMMC_HAS_UPDATED_RESET;
>
> + if (of_find_property(np, "ti,needs-special-hs-handling", NULL))
> + pdata->slots[0].features |= HSMMC_HAS_HSPE_SUPPORT;
> +
> return pdata;
> }
> #else
> --
> 1.7.1
>
> --
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