* [PATCH V3] Set sda-hold-time based on ACPI *CNT value @ 2017-03-28 8:48 Tan Chin Yew 2017-03-28 8:48 ` [PATCH] i2c: designware: Get selected speed mode sda-hold-time via ACPI Tan Chin Yew 0 siblings, 1 reply; 5+ messages in thread From: Tan Chin Yew @ 2017-03-28 8:48 UTC (permalink / raw) To: Wolfram Sang, Jarkko Nikula, Andy Shevchenko, Mika Westerberg Cc: linux-i2c, linux-kernel For I2c to operate correctly under all speed mode, sda-hold-time need to be perfectly tuned. However, sda-hold-time is precalculated according to circuit parameter which make it platform-specific. In order to get accurate sda-hold-time for all platforms, pretuned sda-hold-time for particular platform is stored in ACPI table and driver to load the sda holding time from ACPI table. This patch read the I2c sda-hold-time from ACPI table and assigned the suitable hold time based on the i2c clock frequency. Tested on Intel Apollo Lake. Changes in V3: - Remove null handling in function dw_i2c_acpi_params. - Add descriptions to commit message. Changes in V2: - The code is realigned according to suggestion. - "case 400000:" is added on top of "default:" for readability. Tan Chin Yew (1): i2c: designware: Get selected speed mode sda-hold-time via ACPI drivers/i2c/busses/i2c-designware-platdrv.c | 31 ++++++++++++++++++++--------- 1 file changed, 22 insertions(+), 9 deletions(-) -- 1.9.1 ^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH] i2c: designware: Get selected speed mode sda-hold-time via ACPI 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 2017-03-28 9:13 ` Andy Shevchenko 2017-04-19 18:57 ` Wolfram Sang 0 siblings, 2 replies; 5+ messages in thread From: Tan Chin Yew @ 2017-03-28 8:48 UTC (permalink / raw) To: Wolfram Sang, Jarkko Nikula, Andy Shevchenko, Mika Westerberg Cc: linux-i2c, linux-kernel 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 ^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] i2c: designware: Get selected speed mode sda-hold-time via ACPI 2017-03-28 8:48 ` [PATCH] i2c: designware: Get selected speed mode sda-hold-time via ACPI Tan Chin Yew @ 2017-03-28 9:13 ` Andy Shevchenko 2017-03-31 12:12 ` Jarkko Nikula 2017-04-19 18:57 ` Wolfram Sang 1 sibling, 1 reply; 5+ messages in thread From: Andy Shevchenko @ 2017-03-28 9:13 UTC (permalink / raw) To: Tan Chin Yew, Wolfram Sang, Jarkko Nikula, Mika Westerberg Cc: linux-i2c, linux-kernel On Tue, 2017-03-28 at 16:48 +0800, Tan Chin Yew wrote: > 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> Looks good to me: Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.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) -- Andy Shevchenko <andriy.shevchenko@linux.intel.com> Intel Finland Oy ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] i2c: designware: Get selected speed mode sda-hold-time via ACPI 2017-03-28 9:13 ` Andy Shevchenko @ 2017-03-31 12:12 ` Jarkko Nikula 0 siblings, 0 replies; 5+ messages in thread From: Jarkko Nikula @ 2017-03-31 12:12 UTC (permalink / raw) To: Andy Shevchenko, Tan Chin Yew, Wolfram Sang, Mika Westerberg Cc: linux-i2c, linux-kernel On 03/28/2017 12:13 PM, Andy Shevchenko wrote: > On Tue, 2017-03-28 at 16:48 +0800, Tan Chin Yew wrote: >> 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> > > > Looks good to me: > > Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> > Acked-by: Jarkko Nikula <jarkko.nikula@linux.intel.com> ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] i2c: designware: Get selected speed mode sda-hold-time via ACPI 2017-03-28 8:48 ` [PATCH] i2c: designware: Get selected speed mode sda-hold-time via ACPI Tan Chin Yew 2017-03-28 9:13 ` Andy Shevchenko @ 2017-04-19 18:57 ` Wolfram Sang 1 sibling, 0 replies; 5+ messages in thread From: Wolfram Sang @ 2017-04-19 18:57 UTC (permalink / raw) To: Tan Chin Yew Cc: Jarkko Nikula, Andy Shevchenko, Mika Westerberg, linux-i2c, linux-kernel [-- Attachment #1: Type: text/plain, Size: 445 bytes --] On Tue, Mar 28, 2017 at 04:48:02PM +0800, Tan Chin Yew wrote: > 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> Applied to for-next, thanks! [-- Attachment #2: signature.asc --] [-- Type: application/pgp-signature, Size: 833 bytes --] ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2017-04-19 18:57 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2017-03-28 8:48 [PATCH V3] Set sda-hold-time based on ACPI *CNT value Tan Chin Yew 2017-03-28 8:48 ` [PATCH] i2c: designware: Get selected speed mode sda-hold-time via ACPI Tan Chin Yew 2017-03-28 9:13 ` Andy Shevchenko 2017-03-31 12:12 ` Jarkko Nikula 2017-04-19 18:57 ` Wolfram Sang
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