On 05/22/2017 08:44 AM, Jan Kiszka wrote:
On 2017-05-21 10:09, Ard Biesheuvel wrote:
On 19 May 2017 at 09:56, Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> wrote:
Commit bd698d24b1b57 ("i2c: designware: Get selected speed mode
sda-hold-time via ACPI") updated the logic that reads the timing
parameters for various I2C bus rates from the DSDT, to only read
the timing parameters for the currently selected mode.
This causes a WARN_ON() splat on platforms that legally omit the clock
frequency from the ACPI description, because in the new situation, the
core I2C designware driver still accesses the fields in the driver
struct that we no longer populate, and proceeds to calculate them from
the clock frequency. Since the clock frequency is unspecified, the
driver complains loudly using a WARN_ON().
So revert back to the old situation, where the struct fields for all
timings are populated, but retain the new logic which chooses the SDA
hold time from the timing mode that is currently in use.
Fixes: bd698d24b1b57 ("i2c: designware: Get selected speed mode ...")
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
---
drivers/i2c/busses/i2c-designware-platdrv.c | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)
diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
index f2acd4b6bf01..6283b99d2b17 100644
--- a/drivers/i2c/busses/i2c-designware-platdrv.c
+++ b/drivers/i2c/busses/i2c-designware-platdrv.c
@@ -96,6 +96,7 @@ static int dw_i2c_acpi_configure(struct platform_device *pdev)
struct dw_i2c_dev *dev = platform_get_drvdata(pdev);
acpi_handle handle = ACPI_HANDLE(&pdev->dev);
const struct acpi_device_id *id;
+ u32 ss_ht, fp_ht, hs_ht, fs_ht;
Should these be initialized to zero? I realized that
dw_i2c_acpi_params() could fail, resulting in bogus hold time values
being returnted, but it is unclear to me how that affects the logic in
the core driver.
Oh, indeed, great you found this quickly and we got also report and fix
quickly from Jan. In bad case this could have been difficult to bisect.
I can tell you what happens: this breaks e.g. the Galileo and the
IOT2000 boards. Will send a patch to initialize the vars to 0, restoring
the previous behavior in the absence to the ACPI parameters. The core is
prepared for sda_hold_time == 0.
Yes, i2c-designware-core.c will read the hold time from HW set by
bootloader or the reset default when dev->sda_hold_time is zero.
--
Jarkko
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