From: Samuel Holland <samuel@sholland.org> To: Jassi Brar <jassisinghbrar@gmail.com> Cc: Maxime Ripard <maxime.ripard@free-electrons.com>, Chen-Yu Tsai <wens@csie.org>, Rob Herring <robh+dt@kernel.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, ", linux-arm-kernel"@lists.infradead.org, linux-mediatek@lists.infradead.org, srv_heupstream <linux-arm-kernel@lists.infradead.org>, Devicetree List <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 11:51:59 -0600 [thread overview] Message-ID: <d9e14058-6ffb-e54a-1565-f228342ee1f0@sholland.org> (raw) In-Reply-To: <CABb+yY2uueAK9kzXzU9DT2a4NtV3kK2dc_wtyFWTBn8=Z6Vi7Q@mail.gmail.com> Hi, On 02/28/18 03:16, Jassi Brar wrote: > On Wed, Feb 28, 2018 at 7:57 AM, Samuel Holland <samuel@sholland.org> wrote: > .... > >> +/* >> + * The message box hardware provides 8 unidirectional channels. As the mailbox >> + * framework expects them to be bidirectional >> > That is incorrect. Mailbox framework does not require a channel to be > TX and RX capable. Sorry, it would be more accurate to say that the intended mailbox _client_ expects the channels to be bidirectional. > You should expose each channel as per its physical capability, let the > client configure it for direction (if its bidirectional) and acquire > separate channels for RX and TX if it needs to. Is there any way for the mailbox framework to inform the client that a channel is uni/bidirectional? Or if the channel supports RX/TX specifically? I couldn't find any. It looks like all of the clients assume one case or the other, based on the hardware they were initially designed to support. For example arm_scpi expects one channel per client, while ti_sci and st_remoteproc expect two separate RX and TX channels per client. Since there's no API for the client to know the hardware properties, modifying arm_scpi to support unidirectional mailbox channels would break support for all existing bidirectional mailboxes. To expose the physical channels individually, there would need to be an API to: a) Determine if a mailbox channel supports unidirectional or bidirectional operation. b) If a channel is unidirectional, determine which direction(s) it supports. c) If a unidirectional channel supports both directions, configure which direction it should run in. Since that API doesn't currently exist, I wrote the driver to match what the intended client expected (as all other mailbox controller drivers currently do). > Cheers! Regards, Samuel
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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 11:51:59 -0600 [thread overview] Message-ID: <d9e14058-6ffb-e54a-1565-f228342ee1f0@sholland.org> (raw) In-Reply-To: <CABb+yY2uueAK9kzXzU9DT2a4NtV3kK2dc_wtyFWTBn8=Z6Vi7Q@mail.gmail.com> Hi, On 02/28/18 03:16, Jassi Brar wrote: > On Wed, Feb 28, 2018 at 7:57 AM, Samuel Holland <samuel@sholland.org> wrote: > .... > >> +/* >> + * The message box hardware provides 8 unidirectional channels. As the mailbox >> + * framework expects them to be bidirectional >> > That is incorrect. Mailbox framework does not require a channel to be > TX and RX capable. Sorry, it would be more accurate to say that the intended mailbox _client_ expects the channels to be bidirectional. > You should expose each channel as per its physical capability, let the > client configure it for direction (if its bidirectional) and acquire > separate channels for RX and TX if it needs to. Is there any way for the mailbox framework to inform the client that a channel is uni/bidirectional? Or if the channel supports RX/TX specifically? I couldn't find any. It looks like all of the clients assume one case or the other, based on the hardware they were initially designed to support. For example arm_scpi expects one channel per client, while ti_sci and st_remoteproc expect two separate RX and TX channels per client. Since there's no API for the client to know the hardware properties, modifying arm_scpi to support unidirectional mailbox channels would break support for all existing bidirectional mailboxes. To expose the physical channels individually, there would need to be an API to: a) Determine if a mailbox channel supports unidirectional or bidirectional operation. b) If a channel is unidirectional, determine which direction(s) it supports. c) If a unidirectional channel supports both directions, configure which direction it should run in. Since that API doesn't currently exist, I wrote the driver to match what the intended client expected (as all other mailbox controller drivers currently do). > Cheers! Regards, Samuel
next prev parent reply other threads:[~2018-02-28 17:53 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 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 [this message] 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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