| Message ID | 1462099023-11819-4-git-send-email-yamada.masahiro@socionext.com |
|---|---|
| State | New |
| Headers | show |
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? devm_reset_controller_release() just calls reset_controller_unregister(). It is just a manipulation of a linked list. void reset_controller_unregister(struct reset_controller_dev *rcdev) { mutex_lock(&reset_controller_list_mutex); list_del(&rcdev->list); mutex_unlock(&reset_controller_list_mutex); } -- Best Regards 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(). But, reset_controller_unregister() is just a manipulation of a liked list. It does not trigger any hardware access. Am I wrong? void reset_controller_unregister(struct reset_controller_dev *rcdev) { mutex_lock(&reset_controller_list_mutex); list_del(&rcdev->list); mutex_unlock(&reset_controller_list_mutex); } -- Best Regards Masahiro Yamada
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
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);
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(-) -- 1.9.1