[PATCH v1 2/3] mmc: host: dw_mmc-rockchip: add rockchip,disable-runtime-pm quirk
From: Marco Schirrmeister <hidden>
Date: 2026-01-10 01:07:31
Also in:
linux-devicetree, linux-mmc, linux-rockchip
Subsystem:
arm/rockchip soc support, multimedia card (mmc), secure digital (sd) and sdio subsystem, synopsys designware mmc/sd/sdio driver, the rest · Maintainers:
Heiko Stuebner, Ulf Hansson, Jaehoon Chung, Shawn Lin, Linus Torvalds
The FriendlyElec NanoPi R76S (based on the Rockchip RK3576) suffers from a persistent bus-reset loop on the microSD (dw_mmc) interface during idle periods. When the microSD controller enters runtime-suspend, the subsequent transition back to an active state causes the bus timing to become unstable. This forces the driver to drop the bus speed to 400kHz to perform a full retraining of the SDR104 link. Investigations using the runtime_status interface confirm that preventing the controller from entering a low-power state stabilizes the link and eliminates the reset loop entirely. This patch introduces a new 'rockchip,disable-runtime-pm' Boolean property to the dw_mmc-rockchip driver. The property is used to: - Bypass the 50ms autosuspend delay during the probe sequence. - Explicitly increment the device usage count via pm_runtime_get_noresume() to keep the controller active and prevent it from being suspended during idle periods. Signed-off-by: Marco Schirrmeister <redacted> --- drivers/mmc/host/dw_mmc-rockchip.c | 25 ++++++++++++++++++++++--- 1 file changed, 22 insertions(+), 3 deletions(-)
diff --git a/drivers/mmc/host/dw_mmc-rockchip.c b/drivers/mmc/host/dw_mmc-rockchip.c
index 62c68cda1e21..d3e5c06d80ef 100644
--- a/drivers/mmc/host/dw_mmc-rockchip.c
+++ b/drivers/mmc/host/dw_mmc-rockchip.c@@ -538,6 +538,7 @@ static int dw_mci_rockchip_probe(struct platform_device *pdev) { const struct dw_mci_drv_data *drv_data; const struct of_device_id *match; + bool disable_rpm = of_property_read_bool(pdev->dev.of_node, "rockchip,disable-runtime-pm"); int ret; if (!pdev->dev.of_node)
@@ -549,8 +550,13 @@ static int dw_mci_rockchip_probe(struct platform_device *pdev) pm_runtime_get_noresume(&pdev->dev); pm_runtime_set_active(&pdev->dev); pm_runtime_enable(&pdev->dev); - pm_runtime_set_autosuspend_delay(&pdev->dev, 50); - pm_runtime_use_autosuspend(&pdev->dev); + + /* Only setup autosuspend if the DTS hasn't prohibited it */ + if (!disable_rpm) { + pm_runtime_set_autosuspend_delay(&pdev->dev, 50); + pm_runtime_use_autosuspend(&pdev->dev); + } + ret = dw_mci_pltfm_register(pdev, drv_data); if (ret) {
@@ -560,7 +566,20 @@ static int dw_mci_rockchip_probe(struct platform_device *pdev) return ret; } - pm_runtime_put_autosuspend(&pdev->dev); + /* + * For boards with sensitive signaling like the RK3576-based NanoPi R76S, + * we inhibit runtime PM to prevent bus resets during idle transitions. + */ + if (disable_rpm) { + /* + * Instead of nuclear option (pm_runtime_forbid), we use + * the "soft" way by incrementing the usage count to + * prevent the controller from ever hitting runtime_suspend. + */ + pm_runtime_get_noresume(&pdev->dev); + } else { + pm_runtime_put_autosuspend(&pdev->dev); + } return 0; }
--
2.52.0