[PATCH v1 2/2] bus: mhi: core: Check for device supported event rings and channels

[Hemant Kumar <hemantk@xxxxxxxxxxxxxx>]

It is possible that the device does not support the number of event
rings and channels that the controller would like to use. Read the
MHICFG to determine device-side support and if the controller requests
more than the device supports, bailout without configuring device MMIO
registers.

Signed-off-by: Hemant Kumar <hemantk@xxxxxxxxxxxxxx>
---
 drivers/bus/mhi/core/init.c     | 31 +++++++++++++++++++++++++++++++
 drivers/bus/mhi/core/internal.h |  4 ++++
 2 files changed, 35 insertions(+)

diff --git a/drivers/bus/mhi/core/init.c b/drivers/bus/mhi/core/init.c
index 70fd6af..35a6b1d 100644
--- a/drivers/bus/mhi/core/init.c
+++ b/drivers/bus/mhi/core/init.c
@@ -488,6 +488,37 @@ int mhi_init_mmio(struct mhi_controller *mhi_cntrl)
 		{ 0, 0, 0 }
 	};
 
+	/* range check b/w host and device supported ev rings and channels */
+	ret = mhi_read_reg(mhi_cntrl, base, MHICFG, &val);
+	if (ret) {
+		dev_err(dev, "Unable to read MHICFG register\n");
+		return -EIO;
+	}
+
+	if (MHICFG_NHWER(val) < mhi_cntrl->hw_ev_rings) {
+		dev_err(dev, "#HWEV ring: host requires %d dev supports %d\n",
+			mhi_cntrl->hw_ev_rings, MHICFG_NHWER(val));
+		return -EIO;
+	}
+
+	if (MHICFG_NER(val) < mhi_cntrl->total_ev_rings) {
+		dev_err(dev, "#EV ring: host requires %d dev supports %d\n",
+			mhi_cntrl->total_ev_rings, MHICFG_NER(val));
+		return -EIO;
+	}
+
+	if (MHICFG_NHWCH(val) < mhi_cntrl->hw_chan) {
+		dev_err(dev, "#HWCH: host requires %d dev supports %d\n",
+			mhi_cntrl->hw_chan, MHICFG_NHWCH(val));
+		return -EIO;
+	}
+
+	if (MHICFG_NCH(val) < mhi_cntrl->max_chan) {
+		dev_err(dev, "#CH: host requires %d dev supports %d\n",
+			mhi_cntrl->max_chan, MHICFG_NCH(val));
+		return -EIO;
+	}
+
 	dev_dbg(dev, "Initializing MHI registers\n");
 
 	/* Read channel db offset */
diff --git a/drivers/bus/mhi/core/internal.h b/drivers/bus/mhi/core/internal.h
index 3d8e480..9cbfa71 100644
--- a/drivers/bus/mhi/core/internal.h
+++ b/drivers/bus/mhi/core/internal.h
@@ -28,6 +28,10 @@ extern struct bus_type mhi_bus_type;
 #define MHICFG_NHWCH_SHIFT (8)
 #define MHICFG_NCH_MASK (0xFF)
 #define MHICFG_NCH_SHIFT (0)
+#define MHICFG_NHWER(n) (((n) & MHICFG_NHWER_MASK) >> MHICFG_NHWER_SHIFT)
+#define MHICFG_NER(n) (((n) & MHICFG_NER_MASK) >> MHICFG_NER_SHIFT)
+#define MHICFG_NHWCH(n) (((n) & MHICFG_NHWCH_MASK) >> MHICFG_NHWCH_SHIFT)
+#define MHICFG_NCH(n) (((n) & MHICFG_NCH_MASK) >> MHICFG_NCH_SHIFT)
 
 #define CHDBOFF (0x18)
 #define CHDBOFF_CHDBOFF_MASK (0xFFFFFFFF)
-- 
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