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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Justin He <justin.he@arm.com>,
        Sudeep Holla <sudeep.holla@arm.com>,
        Jassi Brar <jaswinder.singh@linaro.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.16 0536/1039] mailbox: pcc: Handle all PCC subtypes correctly in pcc_mbox_irq
Date:   Mon, 24 Jan 2022 19:38:45 +0100
Message-Id: <20220124184143.297944034@linuxfoundation.org>
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From: Sudeep Holla <sudeep.holla@arm.com>

[ Upstream commit 7215a7857e796c655ae1184b313556102fa8bc40 ]

Commit c45ded7e1135 ("mailbox: pcc: Add support for PCCT extended PCC
subspaces(type 3/4)") enabled the type3/4 of PCCT, but the change in
pcc_mbox_irq breaks the other PCC subtypes.

The kernel reports a warning on an Ampere eMag server

-->8
 CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.16.0-rc4 #127
 Hardware name: MiTAC RAPTOR EV-883832-X3-0001/RAPTOR, BIOS 0.14 02/22/2019
 Call trace:
  dump_backtrace+0x0/0x200
  show_stack+0x20/0x30
  dump_stack_lvl+0x68/0x84
  dump_stack+0x18/0x34
  __report_bad_irq+0x54/0x17c
  note_interrupt+0x330/0x428
  handle_irq_event_percpu+0x90/0x98
  handle_irq_event+0x4c/0x148
  handle_fasteoi_irq+0xc4/0x188
  generic_handle_domain_irq+0x44/0x68
  gic_handle_irq+0x84/0x2ec
  call_on_irq_stack+0x28/0x34
  do_interrupt_handler+0x88/0x90
  el1_interrupt+0x48/0xb0
  el1h_64_irq_handler+0x18/0x28
  el1h_64_irq+0x7c/0x80

Fixes: c45ded7e1135 ("mailbox: pcc: Add support for PCCT extended PCC subspaces(type 3/4)")
Reported-by: Justin He <justin.he@arm.com>
Tested-by: Justin He <justin.he@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/mailbox/pcc.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
index e0a1ab3861f0d..ed18936b8ce68 100644
--- a/drivers/mailbox/pcc.c
+++ b/drivers/mailbox/pcc.c
@@ -241,9 +241,11 @@ static irqreturn_t pcc_mbox_irq(int irq, void *p)
 	if (ret)
 		return IRQ_NONE;
 
-	val &= pchan->cmd_complete.status_mask;
-	if (!val)
-		return IRQ_NONE;
+	if (val) { /* Ensure GAS exists and value is non-zero */
+		val &= pchan->cmd_complete.status_mask;
+		if (!val)
+			return IRQ_NONE;
+	}
 
 	ret = pcc_chan_reg_read(&pchan->error, &val);
 	if (ret)
-- 
2.34.1