From: Samuel Holland <samuel@sholland.org> To: Maxime Ripard <maxime.ripard@bootlin.com> Cc: Chen-Yu Tsai <wens@csie.org>, Jassi Brar <jassisinghbrar@gmail.com>, Rob Herring <robh+dt@kernel.org>, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org, Andre Przywara <andre.przywara@arm.com> Subject: Re: [PATCH 3/3] mailbox: sunxi-msgbox: Add a new mailbox driver Date: Wed, 28 Feb 2018 11:19:11 -0600 [thread overview] Message-ID: <fdf86770-6f45-3b3c-50ea-7a8363894639@sholland.org> (raw) In-Reply-To: <20180228083214.h4oi2kmjjqmoyfhn@flea> Hi, On 02/28/18 02:32, Maxime Ripard wrote: > On Tue, Feb 27, 2018 at 08:27:14PM -0600, Samuel Holland wrote: >> + /* >> + * The failure path should not disable the clock or assert the reset, >> + * because the PSCI implementation in firmware relies on this device >> + * being functional. Claiming the clock in this driver is required to >> + * prevent Linux from turning it off. >> + */ >> + ret = clk_prepare_enable(clk); >> + if (ret) { >> + dev_err(dev, "Failed to enable bus clock: %d\n", ret); >> + return ret; >> + } > > You don't need it to be always on though. You only need it to be > enabled when you access the registers (on both sides I guess?). So you > could very well enable the clock in your registers accessors in Linux, > and do the same in the ARISC firmware. That should work. It does need to always be on because the *PSCI* implementation (ATF) also uses SCPI concurrently with Linux (on a separate channel). Turning off the clock anywhere in Linux could turn it off in the middle of a PSCI SCPI call on a different CPU, causing ATF to hang in EL3 (which would be very bad). > Maxime Regards, Samuel
WARNING: multiple messages have this Message-ID (diff)
From: samuel@sholland.org (Samuel Holland) To: linux-arm-kernel@lists.infradead.org Subject: [PATCH 3/3] mailbox: sunxi-msgbox: Add a new mailbox driver Date: Wed, 28 Feb 2018 11:19:11 -0600 [thread overview] Message-ID: <fdf86770-6f45-3b3c-50ea-7a8363894639@sholland.org> (raw) In-Reply-To: <20180228083214.h4oi2kmjjqmoyfhn@flea> Hi, On 02/28/18 02:32, Maxime Ripard wrote: > On Tue, Feb 27, 2018 at 08:27:14PM -0600, Samuel Holland wrote: >> + /* >> + * The failure path should not disable the clock or assert the reset, >> + * because the PSCI implementation in firmware relies on this device >> + * being functional. Claiming the clock in this driver is required to >> + * prevent Linux from turning it off. >> + */ >> + ret = clk_prepare_enable(clk); >> + if (ret) { >> + dev_err(dev, "Failed to enable bus clock: %d\n", ret); >> + return ret; >> + } > > You don't need it to be always on though. You only need it to be > enabled when you access the registers (on both sides I guess?). So you > could very well enable the clock in your registers accessors in Linux, > and do the same in the ARISC firmware. That should work. It does need to always be on because the *PSCI* implementation (ATF) also uses SCPI concurrently with Linux (on a separate channel). Turning off the clock anywhere in Linux could turn it off in the middle of a PSCI SCPI call on a different CPU, causing ATF to hang in EL3 (which would be very bad). > Maxime Regards, Samuel
next prev parent reply other threads:[~2018-02-28 17:19 UTC|newest] Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-02-28 2:27 [PATCH 0/3] Allwinner sunxi message box support Samuel Holland 2018-02-28 2:27 ` Samuel Holland 2018-02-28 2:27 ` [PATCH 1/3] dt-bindings: Add a binding for the sunxi message box Samuel Holland 2018-02-28 2:27 ` Samuel Holland 2018-02-28 8:28 ` Maxime Ripard 2018-02-28 8:28 ` Maxime Ripard 2018-02-28 17:17 ` Andre Przywara 2018-02-28 17:17 ` Andre Przywara 2018-03-01 10:03 ` Maxime Ripard 2018-03-01 10:03 ` Maxime Ripard 2018-02-28 17:52 ` Samuel Holland 2018-02-28 17:52 ` Samuel Holland 2018-02-28 2:27 ` [PATCH 2/3] mailbox: Avoid NULL dereference in mbox_chan_received_data Samuel Holland 2018-02-28 2:27 ` Samuel Holland 2018-02-28 17:17 ` Andre Przywara 2018-02-28 17:17 ` Andre Przywara 2018-03-01 13:32 ` Jassi Brar 2018-03-01 13:32 ` Jassi Brar 2018-02-28 2:27 ` [PATCH 3/3] mailbox: sunxi-msgbox: Add a new mailbox driver Samuel Holland 2018-02-28 2:27 ` Samuel Holland 2018-02-28 8:32 ` Maxime Ripard 2018-02-28 8:32 ` Maxime Ripard 2018-02-28 17:19 ` Samuel Holland [this message] 2018-02-28 17:19 ` Samuel Holland 2018-03-01 10:32 ` Maxime Ripard 2018-03-01 10:32 ` Maxime Ripard 2018-03-01 11:32 ` Andre Przywara 2018-03-01 11:32 ` Andre Przywara 2018-03-01 11:51 ` Maxime Ripard 2018-03-01 11:51 ` Maxime Ripard 2018-02-28 9:16 ` Jassi Brar 2018-02-28 9:16 ` Jassi Brar 2018-02-28 17:51 ` Samuel Holland 2018-02-28 17:51 ` Samuel Holland 2018-02-28 18:14 ` Jassi Brar 2018-02-28 18:14 ` Jassi Brar 2018-02-28 18:14 ` Jassi Brar 2018-02-28 18:56 ` Samuel Holland 2018-02-28 18:56 ` Samuel Holland 2018-02-28 18:56 ` Samuel Holland 2018-03-01 5:22 ` Jassi Brar 2018-03-01 5:22 ` Jassi Brar 2018-03-01 5:22 ` Jassi Brar 2018-02-28 8:24 ` [PATCH 0/3] Allwinner sunxi message box support Maxime Ripard 2018-02-28 8:24 ` Maxime Ripard 2018-02-28 17:18 ` Samuel Holland 2018-02-28 17:18 ` Samuel Holland 2018-03-01 10:28 ` Maxime Ripard 2018-03-01 10:28 ` Maxime Ripard
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