Hi Arnd, > -----Original Message----- > From: Arnd Bergmann [mailto:arnd@xxxxxxxx] > Sent: Friday, February 18, 2011 4:21 PM > To: zhangfei gao > Cc: Nath, Arindam; cjb@xxxxxxxxxx; linux-mmc@xxxxxxxxxxxxxxx; Su, > Henry; Lu, Aaron; anath.amd@xxxxxxxxx > Subject: Re: [PATCH 01/12] mmc: sdhci: add support for auto CMD23 > > On Friday 18 February 2011 11:45:27 zhangfei gao wrote: > > On Tue, Feb 15, 2011 at 4:34 AM, Arindam Nath <arindam.nath@xxxxxxx> > wrote: > > > Host Controller v3.00 and later support Auto CMD23 in the Transfer > > > Mode register. Since Auto CMD23 can be used with or without DMA, > > > and if used with DMA, it should only be ADMA, we check against > > > SDHCI_USE_SDMA not being set. This flag is reset when > SDHCI_USE_ADMA > > > is set. > > > > > > A new definition for SDHCI_ARGUMENT2 register has been added > > > in v3.00 spec, which is the same as SDHCI_DMA_ADDRESS. We program > the > > > block count for CMD23 in SDHCI_ARGUMENT2, so we don't need CMD12 to > > > stop multiple block transfers. But during error recovery procedure, > > > we will need to send Abort command, so we use a global variable > > > abort_cmd to save the stop command to be used later. > > > > > > Two bits are added to SCR register as per the Physical Layer Spec > v3.01, > > > which specify whether the card supports CMD20 and/or CMD23. We use > this > > > as one of the conditions to decide whether to enable Auto CMD23 or > not. > > > > > > Signed-off-by: Arindam Nath <arindam.nath@xxxxxxx> > > Why are you doing this in the SDHC code and not in the block driver > code? > > AFAICT, whether CMD23 can be used or not is primarily a decision based > on > the card, and the block driver might want issue it for a longer range > if it needs to split a block request into multiple MMC requests. Thanks for the comments. Yes, whether a card supports CMD23 depends on the card, but Auto CMD23 is a feature added to the Host Controller v3.00 just like Auto CMD12. I am already doing a check inside sdhci_host_auto_cmd23_supported() whether the card supports CMD23, and whether the request is for multiple block transfers. Also I tried to make my implementation consistent with Auto CMD12 implementation already there in the sdhc code. Regards, Arindam -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
