diff options
| author | Marc Kleine-Budde <mkl@pengutronix.de> | 2011-01-09 22:46:25 +0100 |
|---|---|---|
| committer | Marc Kleine-Budde <mkl@pengutronix.de> | 2011-01-24 13:24:30 +0100 |
| commit | 9e0a2d1ca3de6e284e99ad5cae1ae33ecb74c479 (patch) | |
| tree | 2055519c8e9459d2f7c09f98440d6f243038fa60 /drivers/net | |
| parent | 0909c1ec6f016b3f580fa2f4630659a5874a8ef8 (diff) | |
can: at91_can: don't use mailbox 0
Due to a chip bug (errata 50.2.6.3 & 50.3.5.3 in
"AT91SAM9263 Preliminary 6249H-ATARM-27-Jul-09") the contents of mailbox
0 may be send under certain conditions (even if disabled or in rx mode).
The workaround in the errata suggests not to use the mailbox and load it
with a unused identifier.
This patch implements the first part of the workaround, it updates
AT91_MB_RX_NUM and AT91_MB_RX_FIRST (and the inline documentation)
so that mailbox 0 stays unused.
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Acked-by: Wolfgang Grandegger <wg@grandegger.com>
Acked-by: Kurt Van Dijck <kurt.van.dijck@eia.be>
Diffstat (limited to 'drivers/net')
| -rw-r--r-- | drivers/net/can/at91_can.c | 32 |
1 files changed, 20 insertions, 12 deletions
diff --git a/drivers/net/can/at91_can.c b/drivers/net/can/at91_can.c index 892c3d8c64a2..16e45a51cbb3 100644 --- a/drivers/net/can/at91_can.c +++ b/drivers/net/can/at91_can.c @@ -40,16 +40,16 @@ #include <mach/board.h> -#define AT91_NAPI_WEIGHT 12 +#define AT91_NAPI_WEIGHT 11 /* * RX/TX Mailbox split * don't dare to touch */ -#define AT91_MB_RX_NUM 12 +#define AT91_MB_RX_NUM 11 #define AT91_MB_TX_SHIFT 2 -#define AT91_MB_RX_FIRST 0 +#define AT91_MB_RX_FIRST 1 #define AT91_MB_RX_LAST (AT91_MB_RX_FIRST + AT91_MB_RX_NUM - 1) #define AT91_MB_RX_MASK(i) ((1 << (i)) - 1) @@ -236,10 +236,14 @@ static void at91_setup_mailboxes(struct net_device *dev) unsigned int i; /* - * The first 12 mailboxes are used as a reception FIFO. The - * last mailbox is configured with overwrite option. The - * overwrite flag indicates a FIFO overflow. + * Due to a chip bug (errata 50.2.6.3 & 50.3.5.3) the first + * mailbox is disabled. The next 11 mailboxes are used as a + * reception FIFO. The last mailbox is configured with + * overwrite option. The overwrite flag indicates a FIFO + * overflow. */ + for (i = 0; i < AT91_MB_RX_FIRST; i++) + set_mb_mode(priv, i, AT91_MB_MODE_DISABLED); for (i = AT91_MB_RX_FIRST; i < AT91_MB_RX_LAST; i++) set_mb_mode(priv, i, AT91_MB_MODE_RX); set_mb_mode(priv, AT91_MB_RX_LAST, AT91_MB_MODE_RX_OVRWR); @@ -541,27 +545,31 @@ static void at91_read_msg(struct net_device *dev, unsigned int mb) * * Theory of Operation: * - * 12 of the 16 mailboxes on the chip are reserved for RX. we split - * them into 2 groups. The lower group holds 8 and upper 4 mailboxes. + * 11 of the 16 mailboxes on the chip are reserved for RX. we split + * them into 2 groups. The lower group holds 7 and upper 4 mailboxes. * * Like it or not, but the chip always saves a received CAN message * into the first free mailbox it finds (starting with the * lowest). This makes it very difficult to read the messages in the * right order from the chip. This is how we work around that problem: * - * The first message goes into mb nr. 0 and issues an interrupt. All + * The first message goes into mb nr. 1 and issues an interrupt. All * rx ints are disabled in the interrupt handler and a napi poll is * scheduled. We read the mailbox, but do _not_ reenable the mb (to * receive another message). * * lower mbxs upper - * ______^______ __^__ - * / \ / \ + * ____^______ __^__ + * / \ / \ * +-+-+-+-+-+-+-+-++-+-+-+-+ - * |x|x|x|x|x|x|x|x|| | | | | + * | |x|x|x|x|x|x|x|| | | | | * +-+-+-+-+-+-+-+-++-+-+-+-+ * 0 0 0 0 0 0 0 0 0 0 1 1 \ mail * 0 1 2 3 4 5 6 7 8 9 0 1 / box + * ^ + * | + * \ + * unused, due to chip bug * * The variable priv->rx_next points to the next mailbox to read a * message from. As long we're in the lower mailboxes we just read the |