From: Wolfram Sang <mailto:wsa@xxxxxxxxxxxxx> Sent: Sunday, August 02, 2015 6:41 AM > To: Gao Pan-B54642 > Cc: linux-i2c@xxxxxxxxxxxxxxx; Li Frank-B20596; Duan Fugang-B38611; > u.kleine-koenig@xxxxxxxxxxxxxx > Subject: Re: [Patch v2] i2c: imx: add runtime pm support to improve the > performance > > On Thu, Jun 18, 2015 at 05:27:31PM +0800, Gao Pan wrote: > > In our former i2c driver, i2c clk is enabled and disabled in xfer > > function, which contributes to power saving. However, the clk enable > > process brings a busy wait delay until the core is stable. As a > > result, the performance is sacrificed. > > > > To weigh the power consumption and i2c bus performance, runtime pm is > > the good solution for it. The clk is enabled when a i2c transfer > > starts, and disabled after a specifically defined delay. > > > > Without the patch the test case (many eeprom reads) executes with > approx: > > real 1m7.735s > > user 0m0.488s > > sys 0m20.040s > > > > With the patch the same test case (many eeprom reads) executes with > approx: > > real 0m54.241s > > user 0m0.440s > > sys 0m5.920s > > > > From the test result, the patch get better performance. > > Looks OK to me. coccicheck says something, though: > > drivers/i2c/busses/i2c-imx.c:1098:7-26: pm_runtime_get_sync returns < 0 > as error. Unecessary IS_ERR_VALUE at line 1099 > drivers/i2c/busses/i2c-imx.c:896:10-29: pm_runtime_get_sync returns < 0 > as error. Unecessary IS_ERR_VALUE at line 897 > > Please fix that and add "kernel@xxxxxxxxxxxxxx" to CC when resending. I > know they use the driver a lot. Thanks, will fix it in next version. > > V2: > > As Uwe Kleine-König's suggestion, the version do below changes: > > - call clk_prepare_enable in probe to avoid never enabling clock > > if CONFIG_PM is disabled > > - enable clock before request IRQ in probe > > - remove the pm staff in i2c_imx_isr > > Thanks for this info. If you could put it below "---" that would be > preferred by me. Thanks. ��.n��������+%������w��{.n�����{��-��)�� jg��� �����ݢj����G���� ���j:+v���w�m������w�������h�����٥
