Re: [PATCH 2/2] mmc: sdhci-esdhc-imx: optimize clock loopback selection with dummy pad support
From: Ulf Hansson <hidden>
Date: 2025-06-09 14:25:33
Also in:
imx, linux-mmc, lkml
On Wed, 21 May 2025 at 04:53, [off-list ref] wrote:
From: Luke Wang <redacted> For legacy platforms without dummy pad: When clock <= 100MHz: Set ESDHC_MIX_CTRL_FBCLK_SEL to 0 (external clock pad loopback) for better bus clock proximity. When clock > 100MHz: Set ESDHC_MIX_CTRL_FBCLK_SEL to 1 (internal clock loopback) to avoid signal reflection noise at high frequency. For i.MX94/95 with dummy pad support: Keep ESDHC_MIX_CTRL_FBCLK_SEL at 0 for all speed mode. Hardware automatically substitutes clock pad loopback with dummy pad loopback when available, eliminating signal reflections while preserving better bus clock proximity. Signed-off-by: Luke Wang <redacted>
Applied for next, thanks! Kind regards Uffe
quoted hunk ↗ jump to hunk
--- drivers/mmc/host/sdhci-esdhc-imx.c | 25 +++++++++++++++++++++---- 1 file changed, 21 insertions(+), 4 deletions(-)diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci-esdhc-imx.c index c448a53530a5..5f1c45b2bd5d 100644 --- a/drivers/mmc/host/sdhci-esdhc-imx.c +++ b/drivers/mmc/host/sdhci-esdhc-imx.c@@ -212,6 +212,9 @@ /* The IP does not have GPIO CD wake capabilities */ #define ESDHC_FLAG_SKIP_CD_WAKE BIT(18) +/* the controller has dummy pad for clock loopback */ +#define ESDHC_FLAG_DUMMY_PAD BIT(19) + #define ESDHC_AUTO_TUNING_WINDOW 3 enum wp_types {@@ -348,6 +351,15 @@ static struct esdhc_soc_data usdhc_imx8mm_data = { .quirks = SDHCI_QUIRK_NO_LED, }; +static struct esdhc_soc_data usdhc_imx95_data = { + .flags = ESDHC_FLAG_USDHC | ESDHC_FLAG_MAN_TUNING + | ESDHC_FLAG_HAVE_CAP1 | ESDHC_FLAG_HS200 + | ESDHC_FLAG_HS400 | ESDHC_FLAG_HS400_ES + | ESDHC_FLAG_STATE_LOST_IN_LPMODE + | ESDHC_FLAG_DUMMY_PAD, + .quirks = SDHCI_QUIRK_NO_LED, +}; + struct pltfm_imx_data { u32 scratchpad; struct pinctrl *pinctrl;@@ -392,6 +404,8 @@ static const struct of_device_id imx_esdhc_dt_ids[] = { { .compatible = "fsl,imx7ulp-usdhc", .data = &usdhc_imx7ulp_data, }, { .compatible = "fsl,imx8qxp-usdhc", .data = &usdhc_imx8qxp_data, }, { .compatible = "fsl,imx8mm-usdhc", .data = &usdhc_imx8mm_data, }, + { .compatible = "fsl,imx94-usdhc", .data = &usdhc_imx95_data, }, + { .compatible = "fsl,imx95-usdhc", .data = &usdhc_imx95_data, }, { .compatible = "fsl,imxrt1050-usdhc", .data = &usdhc_imxrt1050_data, }, { .compatible = "nxp,s32g2-usdhc", .data = &usdhc_s32g2_data, }, { /* sentinel */ }@@ -1424,9 +1438,10 @@ static void esdhc_set_uhs_signaling(struct sdhci_host *host, unsigned timing) break; } - if (timing == MMC_TIMING_UHS_SDR104 || - timing == MMC_TIMING_MMC_HS200 || - timing == MMC_TIMING_MMC_HS400) + if (!(imx_data->socdata->flags & ESDHC_FLAG_DUMMY_PAD) && + (timing == MMC_TIMING_UHS_SDR104 || + timing == MMC_TIMING_MMC_HS200 || + timing == MMC_TIMING_MMC_HS400)) m |= ESDHC_MIX_CTRL_FBCLK_SEL; else m &= ~ESDHC_MIX_CTRL_FBCLK_SEL;@@ -1678,7 +1693,9 @@ static void sdhc_esdhc_tuning_restore(struct sdhci_host *host) writel(reg, host->ioaddr + ESDHC_TUNING_CTRL); reg = readl(host->ioaddr + ESDHC_MIX_CTRL); - reg |= ESDHC_MIX_CTRL_SMPCLK_SEL | ESDHC_MIX_CTRL_FBCLK_SEL; + reg |= ESDHC_MIX_CTRL_SMPCLK_SEL; + if (!(imx_data->socdata->flags & ESDHC_FLAG_DUMMY_PAD)) + reg |= ESDHC_MIX_CTRL_FBCLK_SEL; writel(reg, host->ioaddr + ESDHC_MIX_CTRL); writel(FIELD_PREP(ESDHC_TUNE_CTRL_STATUS_DLY_CELL_SET_PRE_MASK, --2.34.1