linux-kernel - [PATCH v2] i2c: designware: Do not require clock when SSCN and FFCN are provided

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-next>] [day] [month] [year] [list]

Date:	Wed, 16 Dec 2015 20:23:45 -0600
From:	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
To:	<mika.westerberg@...ux.intel.com>, <wsa@...-dreams.de>
CC:	<jarkko.nikula@...ux.intel.com>,
	<andriy.shevchenko@...ux.intel.com>, <lho@....com>,
	<Ken.Xue@....com>, <linux-i2c@...r.kernel.org>,
	<linux-acpi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	"Suravee Suthikulpanit" <Suravee.Suthikulpanit@....com>
Subject: [PATCH v2] i2c: designware: Do not require clock when SSCN and FFCN are provided

The current driver uses input clock source frequency to calculate
values for [SS|FS]_[HC|LC] registers. However, when booting ACPI, we do not
currently have a good way to provide the frequency information.
Instead, we can leverage the SSCN and FFCN ACPI methods, which can be used
to directly provide these values. So, the clock information should
no longer be required during probing.

However, since clk can be invalid, additional checks must be done where
we are making use of it.

Signed-off-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
---

Note: This has been tested on AMD Seattle RevB for both DT and ACPI.

Changes in V2:
    In v1, I disregarded the clock if SSCN and FMCN are provided,
    assuming that it was not needed. That was incorrect assumption,
    and is now fixed in v2.

 drivers/i2c/busses/i2c-designware-platdrv.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
index 8ffc36b..4615fe3 100644
--- a/drivers/i2c/busses/i2c-designware-platdrv.c
+++ b/drivers/i2c/busses/i2c-designware-platdrv.c
@@ -44,6 +44,9 @@
 
 static u32 i2c_dw_get_clk_rate_khz(struct dw_i2c_dev *dev)
 {
+	if (IS_ERR(dev->clk))
+		return 0;
+
 	return clk_get_rate(dev->clk)/1000;
 }
 
@@ -206,9 +209,8 @@ static int dw_i2c_plat_probe(struct platform_device *pdev)
 
 	dev->clk = devm_clk_get(&pdev->dev, NULL);
 	dev->get_clk_rate_khz = i2c_dw_get_clk_rate_khz;
-	if (IS_ERR(dev->clk))
-		return PTR_ERR(dev->clk);
-	clk_prepare_enable(dev->clk);
+	if (!IS_ERR(dev->clk))
+		clk_prepare_enable(dev->clk);
 
 	if (!dev->sda_hold_time && ht) {
 		u32 ic_clk = dev->get_clk_rate_khz(dev);
@@ -297,7 +299,8 @@ static int dw_i2c_plat_suspend(struct device *dev)
 	struct dw_i2c_dev *i_dev = platform_get_drvdata(pdev);
 
 	i2c_dw_disable(i_dev);
-	clk_disable_unprepare(i_dev->clk);
+	if (!IS_ERR(i_dev->clk))
+		clk_disable_unprepare(i_dev->clk);
 
 	return 0;
 }
@@ -307,7 +310,8 @@ static int dw_i2c_plat_resume(struct device *dev)
 	struct platform_device *pdev = to_platform_device(dev);
 	struct dw_i2c_dev *i_dev = platform_get_drvdata(pdev);
 
-	clk_prepare_enable(i_dev->clk);
+	if (!IS_ERR(i_dev->clk))
+		clk_prepare_enable(i_dev->clk);
 
 	if (!i_dev->pm_runtime_disabled)
 		i2c_dw_init(i_dev);
-- 
2.5.0

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/