[PATCH] mmc: sdhci-pci-gli: GL9767: Wait for UHS-II PHY before LPM

[Matthew Schwartz <matthew.schwartz@linux.dev>]

sdhci_gl9767_set_clock() re-enables low power negotiation right after
releasing the UHS-II PHY reset. If the bus then goes idle before the
PHY has settled, every SDHCI MMIO read returns all-ones for about 250
us. sdhci_uhs2_interface_detect() takes that as IF_DETECT and LANE_SYNC
set, so a UHS-I only microSD card is treated as UHS-II. The attach then
either fails with "SDHCI_UHS2_CAPS_PTR(65535) is wrong" or, if the
registers come back before the CAPS_PTR read, runs DEVICE_INIT 30 times
with a 10 second timeout each and delays card detection by 5 minutes.

Config register 0x8CC reads 0x2000 from clock enable until about 250-300
us after the PHY reset release and 0x1000 otherwise. Poll its bit 13
before re-enabling low power negotiation. The register meaning is
inferred from that behaviour, and with the wait in place 12 of 12
UHS-II probes of a UHS-I card correctly found no UHS-II interface.

Fixes: 27dd3b82557a ("mmc: sdhci-pci-gli: enable UHS-II mode for GL9767")
Signed-off-by: Matthew Schwartz <matthew.schwartz@linux.dev>
---
 drivers/mmc/host/sdhci-pci-gli.c | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/host/sdhci-pci-gli.c b/drivers/mmc/host/sdhci-pci-gli.c
index b55618566d651..bd383918d27c7 100644
--- a/drivers/mmc/host/sdhci-pci-gli.c
+++ b/drivers/mmc/host/sdhci-pci-gli.c
@@ -205,6 +205,9 @@
 #define   PCIE_GLI_9767_COMBO_MUX_CTL_RST_EN		  BIT(6)
 #define   PCIE_GLI_9767_COMBO_MUX_CTL_WAIT_PERST_EN	  BIT(10)
 
+#define PCIE_GLI_9767_PHY_STS			0x8CC
+#define   PCIE_GLI_9767_PHY_STS_UHS2_BUSY	  BIT(13)
+
 #define PCIE_GLI_9767_PWR_MACRO_CTL					0x8D0
 #define   PCIE_GLI_9767_PWR_MACRO_CTL_LOW_VOLTAGE			  GENMASK(3, 0)
 #define   PCIE_GLI_9767_PWR_MACRO_CTL_LD0_LOW_OUTPUT_VOLTAGE		  GENMASK(15, 12)
@@ -1190,6 +1193,27 @@ static void gl9767_set_low_power_negotiation(struct pci_dev *pdev, bool enable)
 	gl9767_vhs_read(pdev);
 }
 
+static u32 gl9767_read_phy_sts(struct pci_dev *pdev)
+{
+	u32 value;
+
+	pci_read_config_dword(pdev, PCIE_GLI_9767_PHY_STS, &value);
+
+	return value;
+}
+
+static void sdhci_gl9767_uhs2_wait_phy_ready(struct sdhci_host *host)
+{
+	struct sdhci_pci_slot *slot = sdhci_priv(host);
+	struct pci_dev *pdev = slot->chip->pdev;
+	u32 value;
+
+	if (read_poll_timeout_atomic(gl9767_read_phy_sts, value,
+				     !(value & PCIE_GLI_9767_PHY_STS_UHS2_BUSY),
+				     10, 10000, false, pdev))
+		pr_warn("%s: UHS-II PHY not ready after reset.\n", mmc_hostname(host->mmc));
+}
+
 static void sdhci_gl9767_uhs2_phy_reset(struct sdhci_host *host, bool assert)
 {
 	struct sdhci_pci_slot *slot = sdhci_priv(host);
@@ -1276,9 +1300,12 @@ static void sdhci_gl9767_set_clock(struct sdhci_host *host, unsigned int clock)
 
 	sdhci_enable_clk(host, clk);
 
-	if (mmc_card_uhs2(host->mmc))
+	if (mmc_card_uhs2(host->mmc)) {
 		/* De-assert reset */
 		sdhci_gl9767_uhs2_phy_reset(host, false);
+		/* Low power negotiation before the PHY settles makes MMIO read all-ones */
+		sdhci_gl9767_uhs2_wait_phy_ready(host);
+	}
 
 	gl9767_set_low_power_negotiation(pdev, true);
 }
-- 
2.56.0