Messages in this thread | | | Subject | Re: [PATCH 3/7] reset: lpc18xx: use devm_reset_controller_register() | From | Philipp Zabel <> | Date | Tue, 03 May 2016 13:08:10 +0200 |
| |
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.
regards Philipp
| |