In stm32 sdmmc variant revision v3.0, a block gap hardware flow control
should be used with bus speed modes SDR104 and HS200.
It is enabled by writing a non-null value to the new added register
MMCI_STM32_FIFOTHRR.
The threshold will be 2^(N-1) bytes, so we can use the ffs() function to
compute the value N to be written to the register. The threshold used
should be the data block size, but must not be bigger than the FIFO size.
Signed-off-by: Yann Gautier <yann.gautier@xxxxxxxxxxx>
---
drivers/mmc/host/mmci.h | 5 +++++
drivers/mmc/host/mmci_stm32_sdmmc.c | 13 +++++++++++++
2 files changed, 18 insertions(+)
diff --git a/drivers/mmc/host/mmci.h b/drivers/mmc/host/mmci.h
index b1968cafc58bb..361954249d04d 100644
--- a/drivers/mmc/host/mmci.h
+++ b/drivers/mmc/host/mmci.h
@@ -218,6 +218,11 @@
#define MCI_STM32_BUSYD0ENDMASK BIT(21)
#define MMCIMASK1 0x040
+
+/* STM32 sdmmc data FIFO threshold register */
+#define MMCI_STM32_FIFOTHRR 0x044
+#define MMCI_STM32_THR_MASK GENMASK(3, 0)
+
#define MMCIFIFOCNT 0x048
#define MMCIFIFO 0x080 /* to 0x0bc */
diff --git a/drivers/mmc/host/mmci_stm32_sdmmc.c b/drivers/mmc/host/mmci_stm32_sdmmc.c
index 7f43506b9bb08..0dc1ae674f44c 100644
--- a/drivers/mmc/host/mmci_stm32_sdmmc.c
+++ b/drivers/mmc/host/mmci_stm32_sdmmc.c
@@ -361,6 +361,19 @@ static u32 sdmmc_get_dctrl_cfg(struct mmci_host *host)
datactrl = mmci_dctrl_blksz(host);
+ if (host->hw_revision >= 3) {
+ u32 thr = 0;
+
+ if (host->mmc->ios.timing == MMC_TIMING_UHS_SDR104 ||
+ host->mmc->ios.timing == MMC_TIMING_MMC_HS200) {
+ thr = ffs(min_t(unsigned int, host->data->blksz,
+ host->variant->fifosize));
+ thr = min_t(u32, thr, MMCI_STM32_THR_MASK);
+ }
+
+ writel_relaxed(thr, host->base + MMCI_STM32_FIFOTHRR);
+ }
+
if (host->mmc->card && mmc_card_sdio(host->mmc->card) &&
host->data->blocks == 1)
datactrl |= MCI_DPSM_STM32_MODE_SDIO;
--
2.25.1
