From: Tan Chin Yew <chin.yew.tan@intel.com>
To: Wolfram Sang <wsa@the-dreams.de>,
Jarkko Nikula <jarkko.nikula@linux.intel.com>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] i2c: designware: Get selected speed mode sda-hold-time via ACPI
Date: Tue, 28 Mar 2017 16:48:02 +0800 [thread overview]
Message-ID: <1490690882-11623-2-git-send-email-chin.yew.tan@intel.com> (raw)
In-Reply-To: <1490690882-11623-1-git-send-email-chin.yew.tan@intel.com>
Sda-hold-time is an important parameter for tuning i2c to meet the
electrical specification especially for high speed. I2C with incorrect
sda-hold-time may cause lost arbitration error. Instead of loading all
speed mode settings, only selected speed mode settings are loaded.
Signed-off-by: Tan Chin Yew <chin.yew.tan@intel.com>
---
drivers/i2c/busses/i2c-designware-platdrv.c | 31 ++++++++++++++++++++---------
1 file changed, 22 insertions(+), 9 deletions(-)
diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
index a597ba32..5a4eb6b 100644
--- a/drivers/i2c/busses/i2c-designware-platdrv.c
+++ b/drivers/i2c/busses/i2c-designware-platdrv.c
@@ -85,8 +85,7 @@ static void dw_i2c_acpi_params(struct platform_device *pdev, char method[],
*hcnt = (u16)objs[0].integer.value;
*lcnt = (u16)objs[1].integer.value;
- if (sda_hold)
- *sda_hold = (u32)objs[2].integer.value;
+ *sda_hold = (u32)objs[2].integer.value;
}
kfree(buf.pointer);
@@ -105,14 +104,28 @@ static int dw_i2c_acpi_configure(struct platform_device *pdev)
dev->rx_fifo_depth = 32;
/*
- * Try to get SDA hold time and *CNT values from an ACPI method if
- * it exists for both supported speed modes.
+ * Try to get SDA hold time and *CNT values from an ACPI method for
+ * selected speed modes.
*/
- dw_i2c_acpi_params(pdev, "SSCN", &dev->ss_hcnt, &dev->ss_lcnt, NULL);
- dw_i2c_acpi_params(pdev, "FMCN", &dev->fs_hcnt, &dev->fs_lcnt,
- &dev->sda_hold_time);
- dw_i2c_acpi_params(pdev, "FPCN", &dev->fp_hcnt, &dev->fp_lcnt, NULL);
- dw_i2c_acpi_params(pdev, "HSCN", &dev->hs_hcnt, &dev->hs_lcnt, NULL);
+ switch (dev->clk_freq) {
+ case 100000:
+ dw_i2c_acpi_params(pdev, "SSCN", &dev->ss_hcnt, &dev->ss_lcnt,
+ &dev->sda_hold_time);
+ break;
+ case 1000000:
+ dw_i2c_acpi_params(pdev, "FPCN", &dev->fp_hcnt, &dev->fp_lcnt,
+ &dev->sda_hold_time);
+ break;
+ case 3400000:
+ dw_i2c_acpi_params(pdev, "HSCN", &dev->hs_hcnt, &dev->hs_lcnt,
+ &dev->sda_hold_time);
+ break;
+ case 400000:
+ default:
+ dw_i2c_acpi_params(pdev, "FMCN", &dev->fs_hcnt, &dev->fs_lcnt,
+ &dev->sda_hold_time);
+ break;
+ }
id = acpi_match_device(pdev->dev.driver->acpi_match_table, &pdev->dev);
if (id && id->driver_data)
--
1.9.1
next prev parent reply other threads:[~2017-03-28 8:48 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-28 8:48 [PATCH V3] Set sda-hold-time based on ACPI *CNT value Tan Chin Yew
2017-03-28 8:48 ` Tan Chin Yew [this message]
2017-03-28 9:13 ` [PATCH] i2c: designware: Get selected speed mode sda-hold-time via ACPI Andy Shevchenko
2017-03-31 12:12 ` Jarkko Nikula
2017-04-19 18:57 ` Wolfram Sang
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