[PATCH v2] mmc: sdhci-pci-gli: fix LPM negotiation so x86/S0ix SoCs can suspend

[Sven van Ashbrook]

To improve the r/w performance of GL9763E, the current driver inhibits LPM
negotiation while the device is active.

This prevents a large number of SoCs from suspending, notably x86 systems
which use S0ix as the suspend mechanism:
1. Userspace initiates s2idle suspend (e.g. via writing to
   /sys/power/state)
2. This switches the runtime_pm device state to active, which disables
   LPM negotiation, then calls the "regular" suspend callback
3. With LPM negotiation disabled, the bus cannot enter low-power state
4. On a large number of SoCs, if the bus not in a low-power state, S0ix
   cannot be entered, which in turn prevents the SoC from entering
   suspend.

Fix by re-enabling LPM negotiation in the device's suspend callback.

Suggested-by: Stanislaw Kardach <skardach@xxxxxxxxxx>
Fixes: f9e5b33934ce ("mmc: host: Improve I/O read/write performance for GL9763E")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Sven van Ashbrook <svenva@xxxxxxxxxxxx>
     # on gladios device
     # on 15590.0.0 with v5.10 and upstream (v6.4) kernels

---

Changes in v2:
- improved symmetry and error path in s2idle suspend callback (internal review)

 drivers/mmc/host/sdhci-pci-gli.c | 102 +++++++++++++++++++------------
 1 file changed, 64 insertions(+), 38 deletions(-)

diff --git a/drivers/mmc/host/sdhci-pci-gli.c b/drivers/mmc/host/sdhci-pci-gli.c
index 1792665c9494a..19f577cc8bceb 100644
--- a/drivers/mmc/host/sdhci-pci-gli.c
+++ b/drivers/mmc/host/sdhci-pci-gli.c
@@ -745,42 +745,6 @@ static u32 sdhci_gl9750_readl(struct sdhci_host *host, int reg)
 	return value;
 }
 
-#ifdef CONFIG_PM_SLEEP
-static int sdhci_pci_gli_resume(struct sdhci_pci_chip *chip)
-{
-	struct sdhci_pci_slot *slot = chip->slots[0];
-
-	pci_free_irq_vectors(slot->chip->pdev);
-	gli_pcie_enable_msi(slot);
-
-	return sdhci_pci_resume_host(chip);
-}
-
-static int sdhci_cqhci_gli_resume(struct sdhci_pci_chip *chip)
-{
-	struct sdhci_pci_slot *slot = chip->slots[0];
-	int ret;
-
-	ret = sdhci_pci_gli_resume(chip);
-	if (ret)
-		return ret;
-
-	return cqhci_resume(slot->host->mmc);
-}
-
-static int sdhci_cqhci_gli_suspend(struct sdhci_pci_chip *chip)
-{
-	struct sdhci_pci_slot *slot = chip->slots[0];
-	int ret;
-
-	ret = cqhci_suspend(slot->host->mmc);
-	if (ret)
-		return ret;
-
-	return sdhci_suspend_host(slot->host);
-}
-#endif
-
 static void gl9763e_hs400_enhanced_strobe(struct mmc_host *mmc,
 					  struct mmc_ios *ios)
 {
@@ -1029,6 +993,68 @@ static int gl9763e_runtime_resume(struct sdhci_pci_chip *chip)
 }
 #endif
 
+#ifdef CONFIG_PM_SLEEP
+static int sdhci_pci_gli_resume(struct sdhci_pci_chip *chip)
+{
+	struct sdhci_pci_slot *slot = chip->slots[0];
+
+	pci_free_irq_vectors(slot->chip->pdev);
+	gli_pcie_enable_msi(slot);
+
+	return sdhci_pci_resume_host(chip);
+}
+
+static int gl9763e_resume(struct sdhci_pci_chip *chip)
+{
+	struct sdhci_pci_slot *slot = chip->slots[0];
+	int ret;
+
+	ret = sdhci_pci_gli_resume(chip);
+	if (ret)
+		return ret;
+
+	ret = cqhci_resume(slot->host->mmc);
+	if (ret)
+		return ret;
+
+	/* Disable LPM negotiation to bring device back in sync
+	 * with its runtime_pm state.
+	 */
+	gl9763e_set_low_power_negotiation(slot, false);
+
+	return 0;
+}
+
+static int gl9763e_suspend(struct sdhci_pci_chip *chip)
+{
+	struct sdhci_pci_slot *slot = chip->slots[0];
+	int ret;
+
+	/* Certain SoCs can suspend only with the bus in low-
+	 * power state, notably x86 SoCs when using S0ix.
+	 * Re-enable LPM negotiation to allow entering L1 state
+	 * and entering system suspend.
+	 */
+	gl9763e_set_low_power_negotiation(slot, true);
+
+	ret = cqhci_suspend(slot->host->mmc);
+	if (ret)
+		goto err_suspend;
+
+	ret = sdhci_suspend_host(slot->host);
+	if (ret)
+		goto err_suspend_host;
+
+	return 0;
+
+err_suspend_host:
+	cqhci_resume(slot->host->mmc);
+err_suspend:
+	gl9763e_set_low_power_negotiation(slot, false);
+	return ret;
+}
+#endif
+
 static int gli_probe_slot_gl9763e(struct sdhci_pci_slot *slot)
 {
 	struct pci_dev *pdev = slot->chip->pdev;
@@ -1113,8 +1139,8 @@ const struct sdhci_pci_fixes sdhci_gl9763e = {
 	.probe_slot	= gli_probe_slot_gl9763e,
 	.ops            = &sdhci_gl9763e_ops,
 #ifdef CONFIG_PM_SLEEP
-	.resume		= sdhci_cqhci_gli_resume,
-	.suspend	= sdhci_cqhci_gli_suspend,
+	.resume		= gl9763e_resume,
+	.suspend	= gl9763e_suspend,
 #endif
 #ifdef CONFIG_PM
 	.runtime_suspend = gl9763e_runtime_suspend,
-- 
2.42.0.rc1.204.g551eb34607-goog