From mboxrd@z Thu Jan 1 00:00:00 1970 From: noralf@tronnes.org (=?windows-1252?Q?Noralf_Tr=F8nnes?=) Date: Tue, 12 May 2015 17:28:47 +0200 Subject: [PATCH 2/3 v8] mailbox: Enable BCM2835 mailbox support In-Reply-To: <1430857666-18877-2-git-send-email-eric@anholt.net> References: <1430857666-18877-1-git-send-email-eric@anholt.net> <1430857666-18877-2-git-send-email-eric@anholt.net> Message-ID: <55521C2F.5030809@tronnes.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Den 05.05.2015 22:27, skrev Eric Anholt: > From: Lubomir Rintel > > This mailbox driver provides a single mailbox channel to write 32-bit > values to the VPU and get a 32-bit response. The Raspberry Pi > firmware uses this mailbox channel to implement firmware calls, while > Roku 2 (despite being derived from the same firmware tree) doesn't. > > The driver was originally submitted by Lubomir, based on the > out-of-tree 2708 mailbox driver. Eric Anholt fixed it up for > upstreaming, with the major functional change being that it now has no > notion of multiple channels (since that is a firmware-dependent > concept) and instead the raspberrypi-firmware driver will do that > bit-twiddling in its own messages. > > Signed-off-by: Lubomir Rintel > Signed-off-by: Craig McGeachie > Signed-off-by: Eric Anholt > Cc: Jassi Brar > Acked-by: Stephen Warren > --- [...] > diff --git a/drivers/mailbox/bcm2835-mailbox.c b/drivers/mailbox/bcm2835-mailbox.c [...] > +static bool bcm2835_last_tx_done(struct mbox_chan *link) > +{ > + struct bcm2835_mbox *mbox = bcm2835_link_mbox(link); > + bool ret; > + > + spin_lock(&mbox->lock); > + ret = !(readl(mbox->regs + MAIL0_STA) & ARM_MS_FULL); I don't know how the mailbox framework uses this function, but MAIL0_STA might be wrong here. Phil Elwell detected a bug in the downstream mailbox driver in the mbox_write function where it waits for space to be available in the FIFO. His observation: With the VC reader blocked and the ARM writing, MAIL0_STA reads empty permanently while MAIL1_STA goes from empty (0x40000000) to non-empty (0x00000001-0x00000007) to full (0x80000008). See: https://github.com/raspberrypi/linux/commit/3018d8a0996ad2340ba1b3f473f705ef285b01b5