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."
This information is taking from the v2.50a of the Synopsys Designware Cores
Mobile Storage Host Databook.
Signed-off-by: Dinh Nguyen <dinguyen@xxxxxxxxxx>
---
drivers/mmc/host/dw_mmc.c | 14 ++++++++++++++
include/linux/mmc/dw_mmc.h | 1 +
2 files changed, 15 insertions(+)
diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
index 4bce0de..7075248 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 +972,17 @@ 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;
+ 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;
+ }
+
/*
* Use mirror of ios->clock to prevent race with mmc
* core ios update when finding the minimum.
diff --git a/include/linux/mmc/dw_mmc.h b/include/linux/mmc/dw_mmc.h
index 6ce7d2c..b9bf3b8 100644
--- a/include/linux/mmc/dw_mmc.h
+++ b/include/linux/mmc/dw_mmc.h
@@ -191,6 +191,7 @@ struct dw_mci {
struct regulator *vmmc; /* Power regulator */
unsigned long irq_flags; /* IRQ flags */
int irq;
+ bool use_hold_reg;
};
/* DMA ops for Internal/External DMAC interface */
--
1.7.9.5
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