From: Dinh Nguyen <dinguyen@xxxxxxxxxx>
This patch will enable the SDMMC_CMD_USE_HOLD_REG bit when the slot is
operating all timing modes, except for SDR50, DDR50, SDR104, and MMC_HS200.
According to the Synopsys databook :"To meet the relatively high Input Hold
Time requirement for SDR12, SDR25, and other MMC speed modes, you should
program bit[29]use_hold_Reg of the CMD register to 1'b1;"..."However, for
the higher speed modes of SDR104, SDR50 and DDR50, you can meet the much
smaller Input Hold Time requirement of 0.8ns by bypassing the Hold Register
(Path A in Figure 10-8, programming CMD.use_hold_reg = 1'b0) and then adding
delay elements on the output path as indicated.
Also, "Never set CMD.use_hold_reg = 1 and cclk_in_drv phase shift to 0 at the
same time. This would add an extra one-cycle delay on the output path, resulting
in incorrect behavior."
This information is taking from the v2.50a of the Synopsys Designware Cores
Mobile Storage Host Databook.
Signed-off-by: Dinh Nguyen <dinguyen@xxxxxxxxxx>
---
v2: Add check for cclk_in_drv phase shift in conjunction with use_hold_reg.
---
drivers/mmc/host/dw_mmc.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
include/linux/mmc/dw_mmc.h | 3 +++
2 files changed, 47 insertions(+)
diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
index 4bce0de..9f5492b 100644
--- a/drivers/mmc/host/dw_mmc.c
+++ b/drivers/mmc/host/dw_mmc.c
@@ -279,6 +279,9 @@ static u32 dw_mci_prepare_command(struct mmc_host *mmc, struct mmc_command *cmd)
cmdr |= SDMMC_CMD_DAT_WR;
}
+ if (slot->host->use_hold_reg)
+ cmdr |= SDMMC_CMD_USE_HOLD_REG;
+
if (drv_data && drv_data->prepare_command)
drv_data->prepare_command(slot->host, &cmdr);
@@ -969,6 +972,24 @@ static void dw_mci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
mci_writel(slot->host, UHS_REG, regs);
slot->host->timing = ios->timing;
+ /* Per Synopsys spec, use_hold_reg should be set for all modes except for
+ * high-speed SDR50, DDR50, SDR104, and MMC_HS200. However, use_hold_reg
+ * should be cleared if the cclk_in_drv is 0.
+ */
+ switch (slot->host->timing) {
+ case MMC_TIMING_UHS_SDR50:
+ case MMC_TIMING_UHS_SDR104:
+ case MMC_TIMING_UHS_DDR50:
+ case MMC_TIMING_MMC_HS200:
+ slot->host->use_hold_reg = 0;
+ break;
+ default:
+ slot->host->use_hold_reg = 1;
+ }
+
+ if (slot->host->cclk_in_drv == 0)
+ slot->host->use_hold_reg = 0;
+
/*
* Use mirror of ios->clock to prevent race with mmc
* core ios update when finding the minimum.
@@ -2339,6 +2360,8 @@ static struct dw_mci_board *dw_mci_parse_dt(struct dw_mci *host)
const struct dw_mci_drv_data *drv_data = host->drv_data;
int idx, ret;
u32 clock_frequency;
+ int sdr_timing[2];
+ int ddr_timing[2];
pdata = devm_kzalloc(dev, sizeof(*pdata), GFP_KERNEL);
if (!pdata) {
@@ -2389,6 +2412,25 @@ static struct dw_mci_board *dw_mci_parse_dt(struct dw_mci *host)
if (of_find_property(np, "caps2-mmc-hs200-1_2v", NULL))
pdata->caps2 |= MMC_CAP2_HS200_1_2V_SDR;
+ /* Check for the "samsung,dw-mshc-sdr-timing" and the
+ * "samsung,dw-mshc-ddr-timing" bindings as this will tell us if we
+ * can safely set the SDMMC_CMD_USE_HOLD_REG bit. The second paramater
+ * in these 2 bindings is the value of the cclk_in_drv. If cclk_in_drv
+ * is 0, we cannot set the SDMMC_CMD_USE_HOLD_REG bit. The default
+ * behavior will be to set cclk_in_drv, as some platforms do not have
+ * to set the sdr or ddr timing parameters.
+ */
+ sdr_timing[1] = ddr_timing[1] = 1;
+ of_property_read_u32_array(np,
+ "samsung,dw-mshc-sdr-timing", sdr_timing, 2);
+
+ of_property_read_u32_array(np,
+ "samsung,dw-mshc-ddr-timing", ddr_timing, 2);
+
+ pdata->cclk_in_drv = 1;
+ if ((sdr_timing[1] == 0) || (ddr_timing[1] == 0))
+ pdata->cclk_in_drv = 0;
+
return pdata;
}
@@ -2495,6 +2537,8 @@ int dw_mci_probe(struct dw_mci *host)
goto err_regulator;
}
+ host->cclk_in_drv = host->pdata->cclk_in_drv;
+
host->quirks = host->pdata->quirks;
spin_lock_init(&host->lock);
diff --git a/include/linux/mmc/dw_mmc.h b/include/linux/mmc/dw_mmc.h
index 6ce7d2c..1da20ce 100644
--- a/include/linux/mmc/dw_mmc.h
+++ b/include/linux/mmc/dw_mmc.h
@@ -191,6 +191,8 @@ struct dw_mci {
struct regulator *vmmc; /* Power regulator */
unsigned long irq_flags; /* IRQ flags */
int irq;
+ bool cclk_in_drv;
+ bool use_hold_reg;
};
/* DMA ops for Internal/External DMAC interface */
@@ -238,6 +240,7 @@ struct dw_mci_board {
u32 caps; /* Capabilities */
u32 caps2; /* More capabilities */
u32 pm_caps; /* PM capabilities */
+ bool cclk_in_drv; /*cclk_in_drv phase shift */
/*
* Override fifo depth. If 0, autodetect it from the FIFOTH register,
* but note that this may not be reliable after a bootloader has used
--
1.7.9.5
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