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 patch also checks the IHR(Implement Hold Register) in the HCON
register.
This information is taking from the v2.50a of the Synopsys Designware
Cores
Mobile Storage Host Databook.
Signed-off-by: Dinh Nguyen <dinguyen@xxxxxxxxxx>
Acked-by: Arnd Bergmann <arnd@xxxxxxxx>
Acked-by: Heiko Stuebner <heiko@xxxxxxxxx>
Tested-by: Heiko Stuebner <heiko@xxxxxxxxx>
---
v4: use_hold_reg should be set for all modes when cclk_in_drv is
non-zero.
v3: Read the IHR(Implement Hold Register) in the HCON
v2: Add check for cclk_in_drv phase shift in conjunction with
use_hold_reg.
---
drivers/mmc/host/dw_mmc.c | 52
++++++++++++++++++++++++++++++++++++++++++++
drivers/mmc/host/dw_mmc.h | 4 ++++
include/linux/mmc/dw_mmc.h | 3 +++
3 files changed, 59 insertions(+)
diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
/*
* Use mirror of ios->clock to prevent race with mmc
* core ios update when finding the minimum.
@@ -2339,6 +2361,8 @@ 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 +2413,25 @@ 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;
+
