net: qrtr: Drop the MHI auto_queue feature for IPCR DL channels

[ Upstream commit 51731792a25cb312ca94cdccfa139eb46de1b2ef ]

MHI stack offers the 'auto_queue' feature, which allows the MHI stack to
auto queue the buffers for the RX path (DL channel). Though this feature
simplifies the client driver design, it introduces race between the client
drivers and the MHI stack. For instance, with auto_queue, the 'dl_callback'
for the DL channel may get called before the client driver is fully probed.
This means, by the time the dl_callback gets called, the client driver's
structures might not be initialized, leading to NULL ptr dereference.

Currently, the drivers have to workaround this issue by initializing the
internal structures before calling mhi_prepare_for_transfer_autoqueue().
But even so, there is a chance that the client driver's internal code path
may call the MHI queue APIs before mhi_prepare_for_transfer_autoqueue() is
called, leading to similar NULL ptr dereference. This issue has been
reported on the Qcom X1E80100 CRD machines affecting boot.

So to properly fix all these races, drop the MHI 'auto_queue' feature
altogether and let the client driver (QRTR) manage the RX buffers manually.
In the QRTR driver, queue the RX buffers based on the ring length during
probe and recycle the buffers in 'dl_callback' once they are consumed. This
also warrants removing the setting of 'auto_queue' flag from controller
drivers.

Currently, this 'auto_queue' feature is only enabled for IPCR DL channel.
So only the QRTR client driver requires the modification.

Fixes: 227fee5fc99e ("bus: mhi: core: Add an API for auto queueing buffers for DL channel")
Fixes: 68a838b84eff ("net: qrtr: start MHI channel after endpoit creation")
Reported-by: Johan Hovold <johan@kernel.org>
Closes: https://lore.kernel.org/linux-arm-msm/ZyTtVdkCCES0lkl4@hovoldconsulting.com
Suggested-by: Chris Lew <quic_clew@quicinc.com>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@oss.qualcomm.com>
Reviewed-by: Jeff Hugo <jeff.hugo@oss.qualcomm.com>
Reviewed-by: Loic Poulain <loic.poulain@oss.qualcomm.com>
Acked-by: Jeff Johnson <jjohnson@kernel.org> # drivers/net/wireless/ath/...
Acked-by: Jeff Hugo <jeff.hugo@oss.qualcomm.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20251218-qrtr-fix-v2-1-c7499bfcfbe0@oss.qualcomm.com
Signed-off-by: Sasha Levin <sashal@kernel.org>

1 files changed, 2 insertions, 18 deletions

diff --git a/drivers/bus/mhi/host/pci_generic.c b/drivers/bus/mhi/host/pci_generic.c
index e3bc737313a2..0884a384b77f 100644
--- a/drivers/bus/mhi/host/pci_generic.c
+++ b/drivers/bus/mhi/host/pci_generic.c
@@ -94,22 +94,6 @@ struct mhi_pci_dev_info {
 		.doorbell_mode_switch = false,		\
 	}
 
-#define MHI_CHANNEL_CONFIG_DL_AUTOQUEUE(ch_num, ch_name, el_count, ev_ring) \
-	{						\
-		.num = ch_num,				\
-		.name = ch_name,			\
-		.num_elements = el_count,		\
-		.event_ring = ev_ring,			\
-		.dir = DMA_FROM_DEVICE,			\
-		.ee_mask = BIT(MHI_EE_AMSS),		\
-		.pollcfg = 0,				\
-		.doorbell = MHI_DB_BRST_DISABLE,	\
-		.lpm_notify = false,			\
-		.offload_channel = false,		\
-		.doorbell_mode_switch = false,		\
-		.auto_queue = true,			\
-	}
-
 #define MHI_EVENT_CONFIG_CTRL(ev_ring, el_count) \
 	{					\
 		.num_elements = el_count,	\
@@ -329,7 +313,7 @@ static const struct mhi_channel_config modem_qcom_v1_mhi_channels[] = {
 	MHI_CHANNEL_CONFIG_UL(14, "QMI", 4, 0),
 	MHI_CHANNEL_CONFIG_DL(15, "QMI", 4, 0),
 	MHI_CHANNEL_CONFIG_UL(20, "IPCR", 8, 0),
-	MHI_CHANNEL_CONFIG_DL_AUTOQUEUE(21, "IPCR", 8, 0),
+	MHI_CHANNEL_CONFIG_DL(21, "IPCR", 8, 0),
 	MHI_CHANNEL_CONFIG_UL_FP(34, "FIREHOSE", 32, 0),
 	MHI_CHANNEL_CONFIG_DL_FP(35, "FIREHOSE", 32, 0),
 	MHI_CHANNEL_CONFIG_UL(46, "IP_SW0", 64, 2),
@@ -762,7 +746,7 @@ static const struct mhi_channel_config mhi_telit_fn980_hw_v1_channels[] = {
 	MHI_CHANNEL_CONFIG_UL(14, "QMI", 32, 0),
 	MHI_CHANNEL_CONFIG_DL(15, "QMI", 32, 0),
 	MHI_CHANNEL_CONFIG_UL(20, "IPCR", 16, 0),
-	MHI_CHANNEL_CONFIG_DL_AUTOQUEUE(21, "IPCR", 16, 0),
+	MHI_CHANNEL_CONFIG_DL(21, "IPCR", 16, 0),
 	MHI_CHANNEL_CONFIG_HW_UL(100, "IP_HW0", 128, 1),
 	MHI_CHANNEL_CONFIG_HW_DL(101, "IP_HW0", 128, 2),
 };