On Tue, Apr 03, 2012 at 21:03:40, Marc Kleine-Budde wrote: > On 04/03/2012 04:29 PM, AnilKumar, Chimata wrote: > >>>> 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. > > The c_can already has a c_can_read_reg32() function. It's for example > used in the rx_poll function. You can make it a function pointer (i.e. > pric->read_reg32()) for easy abstraction.
This won't fit for D_CAN case because offsets are different in c_can compared to d_can. For example if I read CONTROL_REG register (0x0) in case of d_can, which will read only control register. In case of c_can it will read CONTROL_REG + STATUS register values in single read > > >>> * 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 > > Maybe you can use the read_reg32 function on both c_can and d_can. Above comment applies here as well > > regards, 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 majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
