linux-kernel - [PATCH 2/11 RFC] misc: rtsx: Confirm that pcie_capability_read

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Date:   Mon,  6 Jul 2020 11:31:12 +0200
From:   Saheed Olayemi Bolarinwa <refactormyself@...il.com>
To:     helgaas@...nel.org, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Bolarinwa Olayemi Saheed <refactormyself@...il.com>,
        bjorn@...gaas.com, skhan@...uxfoundation.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/11 RFC] misc: rtsx: Confirm that pcie_capability_read_word() is successful

From: Bolarinwa Olayemi Saheed <refactormyself@...il.com>

On failure pcie_capability_read_dword() sets it's last parameter, val
to 0. In which case (val & PCI_EXP_DEVCTL2_LTR_EN) evaluates to 0.
However, with Patch 10/10, it is possible that val is set to ~0 on
failure. This would introduce a bug because (x & x) == (~0 & x).

This bug can be avoided without changing the function's behaviour if the
return value of pcie_capability_read_dword is checked to confirm success.

Check the return value of pcie_capability_read_dword() to ensure success.

Suggested-by: Bjorn Helgaas <bjorn@...gaas.com>
Signed-off-by: Bolarinwa Olayemi Saheed <refactormyself@...il.com>

---
 drivers/misc/cardreader/rts5227.c | 5 +++--
 drivers/misc/cardreader/rts5249.c | 5 +++--
 drivers/misc/cardreader/rts5260.c | 5 +++--
 drivers/misc/cardreader/rts5261.c | 5 +++--
 4 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/drivers/misc/cardreader/rts5227.c b/drivers/misc/cardreader/rts5227.c
index 3a9467aaa435..7a20a4898d07 100644
--- a/drivers/misc/cardreader/rts5227.c
+++ b/drivers/misc/cardreader/rts5227.c
@@ -92,6 +92,7 @@ static void rts5227_force_power_down(struct rtsx_pcr *pcr, u8 pm_state)
 static int rts5227_extra_init_hw(struct rtsx_pcr *pcr)
 {
 	u16 cap;
+	int ret;
 
 	rtsx_pci_init_cmd(pcr);
 
@@ -105,8 +106,8 @@ static int rts5227_extra_init_hw(struct rtsx_pcr *pcr)
 	/* LED shine disabled, set initial shine cycle period */
 	rtsx_pci_add_cmd(pcr, WRITE_REG_CMD, OLT_LED_CTL, 0x0F, 0x02);
 	/* Configure LTR */
-	pcie_capability_read_word(pcr->pci, PCI_EXP_DEVCTL2, &cap);
-	if (cap & PCI_EXP_DEVCTL2_LTR_EN)
+	ret = pcie_capability_read_word(pcr->pci, PCI_EXP_DEVCTL2, &cap);
+	if (!ret && (cap & PCI_EXP_DEVCTL2_LTR_EN))
 		rtsx_pci_add_cmd(pcr, WRITE_REG_CMD, LTR_CTL, 0xFF, 0xA3);
 	/* Configure OBFF */
 	rtsx_pci_add_cmd(pcr, WRITE_REG_CMD, OBFF_CFG, 0x03, 0x03);
diff --git a/drivers/misc/cardreader/rts5249.c b/drivers/misc/cardreader/rts5249.c
index 6c6c9e95a29f..2b05e8663431 100644
--- a/drivers/misc/cardreader/rts5249.c
+++ b/drivers/misc/cardreader/rts5249.c
@@ -95,6 +95,7 @@ static void rts5249_init_from_cfg(struct rtsx_pcr *pcr)
 {
 	struct rtsx_cr_option *option = &(pcr->option);
 	u32 lval;
+	int ret;
 
 	if (CHK_PCI_PID(pcr, PID_524A))
 		rtsx_pci_read_config_dword(pcr,
@@ -118,8 +119,8 @@ static void rts5249_init_from_cfg(struct rtsx_pcr *pcr)
 	if (option->ltr_en) {
 		u16 val;
 
-		pcie_capability_read_word(pcr->pci, PCI_EXP_DEVCTL2, &val);
-		if (val & PCI_EXP_DEVCTL2_LTR_EN) {
+		ret = pcie_capability_read_word(pcr->pci, PCI_EXP_DEVCTL2, &val);
+		if (!ret && (val & PCI_EXP_DEVCTL2_LTR_EN)) {
 			option->ltr_enabled = true;
 			option->ltr_active = true;
 			rtsx_set_ltr_latency(pcr, option->ltr_active_latency);
diff --git a/drivers/misc/cardreader/rts5260.c b/drivers/misc/cardreader/rts5260.c
index 7a9dbb778e84..934aeaeebfaf 100644
--- a/drivers/misc/cardreader/rts5260.c
+++ b/drivers/misc/cardreader/rts5260.c
@@ -498,6 +498,7 @@ static void rts5260_init_from_cfg(struct rtsx_pcr *pcr)
 {
 	struct rtsx_cr_option *option = &pcr->option;
 	u32 lval;
+	int ret;
 
 	rtsx_pci_read_config_dword(pcr, PCR_ASPM_SETTING_5260, &lval);
 
@@ -518,8 +519,8 @@ static void rts5260_init_from_cfg(struct rtsx_pcr *pcr)
 	if (option->ltr_en) {
 		u16 val;
 
-		pcie_capability_read_word(pcr->pci, PCI_EXP_DEVCTL2, &val);
-		if (val & PCI_EXP_DEVCTL2_LTR_EN) {
+		ret = pcie_capability_read_word(pcr->pci, PCI_EXP_DEVCTL2, &val);
+		if (!ret && (val & PCI_EXP_DEVCTL2_LTR_EN)) {
 			option->ltr_enabled = true;
 			option->ltr_active = true;
 			rtsx_set_ltr_latency(pcr, option->ltr_active_latency);
diff --git a/drivers/misc/cardreader/rts5261.c b/drivers/misc/cardreader/rts5261.c
index 195822ec858e..2b6f61696e19 100644
--- a/drivers/misc/cardreader/rts5261.c
+++ b/drivers/misc/cardreader/rts5261.c
@@ -438,9 +438,10 @@ static void rts5261_init_from_cfg(struct rtsx_pcr *pcr)
 	rtsx_pci_write_register(pcr, ASPM_FORCE_CTL, 0xFF, 0);
 	if (option->ltr_en) {
 		u16 val;
+		int ret;
 
-		pcie_capability_read_word(pcr->pci, PCI_EXP_DEVCTL2, &val);
-		if (val & PCI_EXP_DEVCTL2_LTR_EN) {
+		ret = pcie_capability_read_word(pcr->pci, PCI_EXP_DEVCTL2, &val);
+		if (!ret && (val & PCI_EXP_DEVCTL2_LTR_EN)) {
 			option->ltr_enabled = true;
 			option->ltr_active = true;
 			rtsx_set_ltr_latency(pcr, option->ltr_active_latency);
-- 
2.18.2