Messages in this thread | | | Date | Tue, 3 May 2016 20:40:49 +0900 | Subject | Re: [PATCH 3/7] reset: lpc18xx: use devm_reset_controller_register() | From | Masahiro Yamada <> |
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2016-05-03 20:08 GMT+09:00 Philipp Zabel <p.zabel@pengutronix.de>: > Am Dienstag, den 03.05.2016, 19:25 +0900 schrieb Masahiro Yamada: >> Hi Philipp, >> >> 2016-05-03 18:05 GMT+09:00 Philipp Zabel <p.zabel@pengutronix.de>: >> > Am Dienstag, den 03.05.2016, 00:52 +0900 schrieb Masahiro Yamada: >> >> 2016-05-02 17:26 GMT+09:00 Philipp Zabel <p.zabel@pengutronix.de>: >> >> > Am Sonntag, den 01.05.2016, 19:36 +0900 schrieb Masahiro Yamada: >> >> >> Use devm_reset_controller_register() for the reset controller >> >> >> registration and remove the unregister call from the .remove callback. >> >> >> >> >> >> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> >> >> >> --- >> >> >> >> >> >> drivers/reset/reset-lpc18xx.c | 4 +--- >> >> >> 1 file changed, 1 insertion(+), 3 deletions(-) >> >> >> >> >> >> diff --git a/drivers/reset/reset-lpc18xx.c b/drivers/reset/reset-lpc18xx.c >> >> >> index 3b8a4f5..dd4f27e 100644 >> >> >> --- a/drivers/reset/reset-lpc18xx.c >> >> >> +++ b/drivers/reset/reset-lpc18xx.c >> >> >> @@ -199,7 +199,7 @@ static int lpc18xx_rgu_probe(struct platform_device *pdev) >> >> >> >> >> >> platform_set_drvdata(pdev, rc); >> >> >> >> >> >> - ret = reset_controller_register(&rc->rcdev); >> >> >> + ret = devm_reset_controller_register(&pdev->dev, &rc->rcdev); >> >> >> if (ret) { >> >> >> dev_err(&pdev->dev, "unable to register device\n"); >> >> >> goto dis_clks; >> >> >> @@ -229,8 +229,6 @@ static int lpc18xx_rgu_remove(struct platform_device *pdev) >> >> >> if (ret) >> >> >> dev_warn(&pdev->dev, "failed to unregister restart handler\n"); >> >> >> >> >> >> - reset_controller_unregister(&rc->rcdev); >> >> >> - >> >> >> clk_disable_unprepare(rc->clk_delay); >> >> >> clk_disable_unprepare(rc->clk_reg); >> >> >> >> >> > >> >> > Hmm, would this patch theoretically allow a window between the calls to >> >> > clk_disable_unprepare(clk_reg) and devm_reset_controller_release() where >> >> > reset_control_get() + reset_control_(de)assert() would access unclocked >> >> > registers? >> >> >> >> This is not clear to me. >> >> >> >> Why reset_control_get() + reset_control_(de)assert() would happen here? >> > >> > I suppose on a non-SMP device, without parallel probing this can't >> > really happen in practice. >> > It still seems weird that suddenly we disable the clocks before >> > unregistering the reset controller instead of afterwards. >> > >> >> I still do not understand what you mean. >> >> This patch moves the reset_controller_unregister() call >> after clk_disable_unprepare(). > > And so the register access is made impossible before the reset > controller device actually vanishes from the publicly visible list. > >> But, reset_controller_unregister() is just a manipulation of a liked list. >> It does not trigger any hardware access. >> >> Am I wrong? > > No, you are perfectly right. I don't see how this can be a real problem > unless at the same time another driver could try to request the still > available reset control.
Ah, now I understood. Thanks!
-- Best Regards Masahiro Yamada
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