RE: [PATCH v2 4/5] mmc: dw-mmc: add the use_hold_reg in CMD register

[Seungwon Jeon <tgih.jun@samsung.com>]

On Tuesday, August 29, 2012, Jaehoon Chung <jh80.chung@samsung.com> wrote:
> On 08/29/2012 10:21 AM, Seungwon Jeon wrote:
> > On Tuesday, August 28, 2012, Jaehoon Chung <jh80.chung@samsung.com> wrote:
> >> This patch is added the use_hold_reg bit in CMD register.
> >>
> >> In upper version than 2.40a, bit[29] of CMD register is used the use_hold_reg.
> >> Some SoC is affected by this bit.
> >> (This bit means whether use hold register when send data and cmd.
> >>  And related with cclk_in_drv phase)
> >>
> >> Now i known that HOLD-register is using only Exynos-SoC.
> >> But hold-register is supported basically feature at Synopsys-IP.
> >> If Other SoC is used hold regster, we can change the _CLKSEL_REG_.
> >>
> >> Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
> >> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
> >> ---
> >>  drivers/mmc/host/dw_mmc.c  |   36 ++++++++++++++++++++++++++++++++++++
> >>  drivers/mmc/host/dw_mmc.h  |    1 +
> >>  include/linux/mmc/dw_mmc.h |    3 +++
> >>  3 files changed, 40 insertions(+), 0 deletions(-)
> >>
> >> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
> >> index 437fdf8..3642455 100644
> >> --- a/drivers/mmc/host/dw_mmc.c
> >> +++ b/drivers/mmc/host/dw_mmc.c
> >> @@ -265,11 +265,45 @@ static u32 dw_mci_prepare_command(struct mmc_host *mmc, struct mmc_command
> *cmd)
> >>  static void dw_mci_start_command(struct dw_mci *host,
> >>  				 struct mmc_command *cmd, u32 cmd_flags)
> >>  {
> >> +	struct dw_mci_slot *slot = host->cur_slot;
> >> +	struct mmc_ios *ios = &slot->mmc->ios;
> >> +
> >>  	host->cmd = cmd;
> >>  	dev_vdbg(&host->dev,
> >>  		 "start command: ARGR=0x%08x CMDR=0x%08x\n",
> >>  		 cmd->arg, cmd_flags);
> >>
> >> +	if (host->quirks & DW_MCI_QUIRK_USE_CLKSEL_REG) {
> > What is this quirk for?
> CLKSEL register is only used at the Exynos-SoC.
> I didn't know which SoC is used. I added the quirks for Exynos using the CLKSEL register.
You wrapped the access to the CLKSEL register by callback function?
CLKSEL is just implementation for Synopsys's phase-shift technique in Exynos
We don't need to consider this register.
Perhaps, below conditions for hold_reg are only for Exynos?
Which manual did you refer to?

> > Could you explain?
> >
> >> +		/*
> >> +		 * If use HOLD register and SDR12/SDSR25,
> >> +		 * CMD and DATA sent to card through HOLD regster by default.
> >> +		 * But if mode is SDR50/DDR50/SDR104,
> >> +		 * only use the hold register when cclk_in_drv value is greater than 0.
> >> +		 */
> >> +		switch (ios->timing) {
> >> +		case MMC_TIMING_UHS_SDR50:
> >> +		case MMC_TIMING_UHS_DDR50:
> >> +		case MMC_TIMING_UHS_SDR104:
> >> +			if (host->pdata->get_clk_drv &&
> >> +					host->pdata->get_clk_drv(host) &&
> >> +					host->use_hold_reg) {
> >> +				cmd_flags |= SDMMC_CMD_USE_HOLD_REG;
> >> +				break;
> >> +			}
> >> +
> >> +			cmd_flags &= ~SDMMC_CMD_USE_HOLD_REG;
> >> +			break;
> >> +		case MMC_TIMING_UHS_SDR12:
> >> +		case MMC_TIMING_UHS_SDR25:
> >> +			if (host->use_hold_reg) {
> >> +				cmd_flags |= SDMMC_CMD_USE_HOLD_REG;
> >> +				break;
> >> +			}
> >> +		default:
> >> +			cmd_flags &= ~SDMMC_CMD_USE_HOLD_REG;
> >> +		}
> >> +	}
> >> +
> > Considering MMC_TIMING_MMC_HS, MMC_TIMING_SD_HS is omitted.
> Sorry, i will fix.
> > Didn't you consider moving this whole routine to dw_mci_set_ios?
> > When deciding the timing, once seems to be enough.
> Well, i considered that move the code into dw_mci_set_ios().
> But cmd_flags is set before sending the command at every time.
> Finally, hold_regs bit must be also set at every time.
> We can prevent to set the cmd_flags at every time.
Yes, use_hold_regs shoud be set to CMD, whenever sending command.
But cmd_flags for use_hold_reg  can be set a time.

Thanks,
Seungwon Jeon

> 
> Best Regards,
> Jaehoon Chung
> >
> > Thanks,
> > Seungwon Jeon
> >
> >>  	mci_writel(host, CMDARG, cmd->arg);
> >>  	wmb();
> >>
> >> @@ -2015,6 +2049,8 @@ int dw_mci_probe(struct dw_mci *host)
> >>  		host->data_shift = 2;
> >>  	}
> >>
> >> +	host->use_hold_reg = (mci_readl(host, HCON) >> 22) & 0x1;
> >> +
> >>  	/* Reset all blocks */
> >>  	if (!mci_wait_reset(&host->dev, host))
> >>  		return -ENODEV;
> >> diff --git a/drivers/mmc/host/dw_mmc.h b/drivers/mmc/host/dw_mmc.h
> >> index b6a1a78..cc905ee 100644
> >> --- a/drivers/mmc/host/dw_mmc.h
> >> +++ b/drivers/mmc/host/dw_mmc.h
> >> @@ -111,6 +111,7 @@
> >>  #define SDMMC_INT_ERROR			0xbfc2
> >>  /* Command register defines */
> >>  #define SDMMC_CMD_START			BIT(31)
> >> +#define SDMMC_CMD_USE_HOLD_REG		BIT(29)
> >>  #define SDMMC_CMD_CCS_EXP		BIT(23)
> >>  #define SDMMC_CMD_CEATA_RD		BIT(22)
> >>  #define SDMMC_CMD_UPD_CLK		BIT(21)
> >> diff --git a/include/linux/mmc/dw_mmc.h b/include/linux/mmc/dw_mmc.h
> >> index f20979c..803a80d 100644
> >> --- a/include/linux/mmc/dw_mmc.h
> >> +++ b/include/linux/mmc/dw_mmc.h
> >> @@ -156,6 +156,7 @@ struct dw_mci {
> >>  	u32			fifoth_val;
> >>  	u16			verid;
> >>  	u16			data_offset;
> >> +	bool			use_hold_reg;
> >>  	struct device		dev;
> >>  	struct dw_mci_board	*pdata;
> >>  	struct dw_mci_slot	*slot[MAX_MCI_SLOTS];
> >> @@ -201,6 +202,8 @@ struct dw_mci_dma_ops {
> >>  #define DW_MCI_QUIRK_HIGHSPEED			BIT(2)
> >>  /* Unreliable card detection */
> >>  #define DW_MCI_QUIRK_BROKEN_CARD_DETECTION	BIT(3)
> >> +/* To use the CLKSEL register for phase-shift */
> >> +#define DW_MCI_QUIRK_USE_CLKSEL_REG		BIT(4)
> >>
> >>
> >>  struct dma_pdata;
> >> --
> >> 1.7.4.1
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-mmc" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-mmc" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html