linux-kernel - [PATCH v3 08/13] mailbox: pcc: Refactor and simplify check_and

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20250313-pcc_fixes_updates-v3-8-019a4aa74d0f@arm.com>
Date: Thu, 13 Mar 2025 15:28:54 +0000
From: Sudeep Holla <sudeep.holla@....com>
To: linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: Sudeep Holla <sudeep.holla@....com>, 
 Jassi Brar <jassisinghbrar@...il.com>, Huisong Li <lihuisong@...wei.com>, 
 Adam Young <admiyo@...amperecomputing.com>, 
 Robbie King <robbiek@...ghtlabs.com>
Subject: [PATCH v3 08/13] mailbox: pcc: Refactor and simplify
 check_and_ack()

The existing check_and_ack() function had unnecessary complexity. The
logic could be streamlined to improve code readability and maintainability.

The command update register needs to be updated in order to acknowledge
the platform notification through type 4 channel. So it can be done
unconditionally. Currently it is complicated just to make use of
pcc_send_data() which also executes the same updation.

In order to simplify, let us just ring the doorbell directly from
check_and_ack() instead of calling into pcc_send_data(). While at it,
rename it into pcc_chan_check_and_ack() to maintain consistency in the
driver.

Acked-by: Huisong Li <lihuisong@...wei.com>
Tested-by: Adam Young <admiyo@...amperecomputing.com>
Signed-off-by: Sudeep Holla <sudeep.holla@....com>
---
 drivers/mailbox/pcc.c | 37 +++++++++++++------------------------
 1 file changed, 13 insertions(+), 24 deletions(-)

diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
index d6671c18750eaa7de92f49d1ec9ad97eedadec1d..f6714c233f5ab740cb43259ca9306ac6e85f5e4b 100644
--- a/drivers/mailbox/pcc.c
+++ b/drivers/mailbox/pcc.c
@@ -117,8 +117,6 @@ struct pcc_chan_info {
 static struct pcc_chan_info *chan_info;
 static int pcc_chan_count;
 
-static int pcc_send_data(struct mbox_chan *chan, void *data);
-
 /*
  * PCC can be used with perf critical drivers such as CPPC
  * So it makes sense to locally cache the virtual address and
@@ -288,33 +286,24 @@ static int pcc_mbox_error_check_and_clear(struct pcc_chan_info *pchan)
 	return 0;
 }
 
-static void check_and_ack(struct pcc_chan_info *pchan, struct mbox_chan *chan)
+static void pcc_chan_acknowledge(struct pcc_chan_info *pchan)
 {
-	struct acpi_pcct_ext_pcc_shared_memory pcc_hdr;
+	struct acpi_pcct_ext_pcc_shared_memory __iomem *pcc_hdr;
 
 	if (pchan->type != ACPI_PCCT_TYPE_EXT_PCC_SLAVE_SUBSPACE)
 		return;
-	/* If the memory region has not been mapped, we cannot
-	 * determine if we need to send the message, but we still
-	 * need to set the cmd_update flag before returning.
-	 */
-	if (pchan->chan.shmem == NULL) {
-		pcc_chan_reg_read_modify_write(&pchan->cmd_update);
-		return;
-	}
-	memcpy_fromio(&pcc_hdr, pchan->chan.shmem,
-		      sizeof(struct acpi_pcct_ext_pcc_shared_memory));
+
+	pcc_chan_reg_read_modify_write(&pchan->cmd_update);
+
+	pcc_hdr = pchan->chan.shmem;
+
 	/*
-	 * The PCC slave subspace channel needs to set the command complete bit
-	 * after processing message. If the PCC_ACK_FLAG is set, it should also
-	 * ring the doorbell.
-	 *
-	 * The PCC master subspace channel clears chan_in_use to free channel.
+	 * The PCC slave subspace channel needs to set the command
+	 * complete bit after processing message. If the PCC_ACK_FLAG
+	 * is set, it should also ring the doorbell.
 	 */
-	if (pcc_hdr.flags & PCC_CMD_COMPLETION_NOTIFY)
-		pcc_send_data(chan, NULL);
-	else
-		pcc_chan_reg_read_modify_write(&pchan->cmd_update);
+	if (ioread32(&pcc_hdr->flags) & PCC_CMD_COMPLETION_NOTIFY)
+		pcc_chan_reg_read_modify_write(&pchan->db);
 }
 
 /**
@@ -353,7 +342,7 @@ static irqreturn_t pcc_mbox_irq(int irq, void *p)
 	pchan->chan_in_use = false;
 	mbox_chan_received_data(chan, NULL);
 
-	check_and_ack(pchan, chan);
+	pcc_chan_acknowledge(pchan);
 
 	return IRQ_HANDLED;
 }

-- 
2.34.1