On Tue, Apr 03, 2012 at 19:19:32, Marc Kleine-Budde wrote: > 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? In some cases (D_CAN_TXRQ, D_CAN_INTPND, D_CAN_MSGVAL) I have used all the bits, in some cases used few bits. Roughly I can say that its (higher 16bits) % of usages is similar as compare to 16bits While checking the status of TXRequest registers and INT pending register, which is a hot code path, we have to put if checks for register access. > > > * 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? I am pointing out some of the resisters * Single registers in case of D_CAN but multiple register in case of C_CAN So masks will change MASK, ARB, INTPND * D_CAN_IFCMD is the combination of COMM request and COMM mask registers > > > * 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? Right now I added only CAN functionality, in that I am using two set of interface registers (0 and 1). Based on other features status register are extended, we have to handle those as well. > > > * 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 | > > -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
