On 04/03/2012 03:41 PM, AnilKumar, Chimata wrote: > Hi Wolfgang, > > Thanks for reviewing the patch > > On Tue, Apr 03, 2012 at 18:14:55, Wolfgang Grandegger wrote: >> On 04/03/2012 02:32 PM, AnilKumar Ch wrote: >>> This patch adds the support for Bosch D_CAN controller. >>> >>> Bosch D_CAN controller is a full-CAN implementation compliant to >>> CAN protocol version 2.0 part A and B. Bosch D_CAN user manual >>> can be obtained from: http://www.semiconductors.bosch.de/media/ >>> en/pdf/ipmodules_1/can/d_can_users_manual_111.pdf >>> >>> D_CAN device is used on many SoCs like AM335x, DM8148 and DM813x >>> EVMs from TI, D_CAN details on AM335x can be accessed from: >>> http://www.ti.com/lit/ug/spruh73c/spruh73c.pdf >>> >>> D_CAN can be configurable for 16, 32, 64 and 128 message objects. >>> The driver implementation is based on 64 message objects. >>> >>> Following are the design choices made while writing the controller >>> driver: >>> 1. Interface Register set IF0 has be used for receive and IF1 is >>> used for transmit message objects. >>> 2. Out of the total Message objects available, half of it are kept >>> aside for RX purposes and the rest for TX purposes. >>> 3. NAPI implementation is such that both the TX and RX paths >>> functions in polling mode. >>> >>> Signed-off-by: AnilKumar Ch <anilkumar@xxxxxx> >> >> Please explain why this CAN controller cannot be handled by the existing >> C_CAN driver, eventually with some extensions. The register layout seems >> almost identical, at least. >> >> Wolfgang. >> > > These are the some of the pointers I can say, why I had gone for separate > file instead of existing driver: > * In case of D_CAN driver we can see all the registers are 32bit length > but in case of C_CAN registers are in 16bit length. How many bits in these 32 bit registers are used? > * Some of the registers, bit masks are different, so we have to add > checks on every API for differentiating the kind of device Which registers are this? Can you give us an example? > * In case of D_CAN we have some extra features like direct message RAM > access, DMA support, TX/RX pins can be used as GPIO lines (if applicable), > more interrupt lines and three sets of interface registers. Which of these features are used in you driver? > * Wait timings while init bit set/reset during bit-timing initialization > are different in both the cases That's not the hot code path, so some ifs shouldn't hurt. > * bittiming configurations are different. see above. Marc -- Pengutronix e.K. | Marc Kleine-Budde | Industrial Linux Solutions | Phone: +49-231-2826-924 | Vertretung West/Dortmund | Fax: +49-5121-206917-5555 | Amtsgericht Hildesheim, HRA 2686 | http://www.pengutronix.de |
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