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can: mscan: add a comment on reg to idx mapping

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add a comment about the magic of deriving an MSCAN component index
from the peripheral's physical address / register offset

Cc: linux-can@vger.kernel.org
Cc: netdev@vger.kernel.org
Signed-off-by: Gerhard Sittig <gsi@denx.de>
Signed-off-by: Anatolij Gustschin <agust@denx.de>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
This commit is contained in:
Gerhard Sittig 2013-08-23 13:09:02 +02:00 committed by Marc Kleine-Budde
parent 7ec06da81d
commit 3a09b12e0c
1 changed files with 4 additions and 1 deletions
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5
drivers/net/can/mscan/mpc5xxx_can.c
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@ -148,7 +148,10 @@ static u32 mpc512x_can_get_clock(struct platform_device *ofdev,
goto exit_put;
}
/* Determine the MSCAN device index from the physical address */
/* Determine the MSCAN device index from the peripheral's
* physical address. Register address offsets against the
* IMMR base are: 0x1300, 0x1380, 0x2300, 0x2380
*/
pval = of_get_property(ofdev->dev.of_node, "reg", &plen);
BUG_ON(!pval || plen < sizeof(*pval));
clockidx = (*pval & 0x80) ? 1 : 0;