* Singh, Vimal <[email protected]> [090605 05:00]: > > > On Thu, Jun 4, 2009 at 8:58 PM, Tony Lindgren<[email protected]> wrote: > > * vimal singh <[email protected]> [090604 02:34]: > >> On Wed, Jun 3, 2009 at 10:03 PM, Tony Lindgren <[email protected]> wrote: > >> > * Singh, Vimal > >> <[email protected]> [090602 > >> 23:46]: > >> >> > >> >> On Wed, Jun 3, 2009 at 2:06 AM, Tony Lindgren <[email protected]> wrote: > >> >> > * vimal singh <[email protected]> [090602 05:40]: > >> >> >> This patch adds prefetch support to access nand flash in both mpu > >> >> >> and dma > >> mode. > >> >> >> This patch also adds 8-bit nand support (omap_read/write_buf8). > >> >> >> Prefetch can be used for both 8- and 16-bit devices. > >> >> > > >> >> > This should be reviewed on the [email protected] list for > >> >> > sure. > >> >> > One other comment below. > >> >> > > >> >> >> Signed-off-by: Vimal Singh <[email protected]> > >> >> >> --- > >> >> >> I prepared this patch on top of "OMAP2 / OMAP3 NAND driver" patch: > >> >> >> http://lists.infradead.org/pipermail/linux-mtd/2009-May/025562.html > >> >> >> > >> >> >> --- > >> >> >> arch/arm/mach-omap2/gpmc.c | 102 ++++++++++ > >> >> >> arch/arm/plat-omap/include/mach/gpmc.h | 4 > >> >> >> drivers/mtd/nand/Kconfig | 17 + > >> >> >> drivers/mtd/nand/omap2.c | 308 > >> ++++++++++++++++++++++++++++++++- > >> >> >> 4 files changed, 422 insertions(+), 9 deletions(-) > >> >> >> > >> >> >> Index: mtd-2.6/arch/arm/mach-omap2/gpmc.c > >> >> >> =================================================================== > >> >> >> --- mtd-2.6.orig/arch/arm/mach-omap2/gpmc.c > >> >> >> +++ mtd-2.6/arch/arm/mach-omap2/gpmc.c > >> >> >> @@ -54,6 +54,12 @@ > >> >> >> #define GPMC_CHUNK_SHIFT 24 /* 16 MB */ > >> >> >> #define GPMC_SECTION_SHIFT 28 /* 128 MB */ > >> >> >> > >> >> >> +#ifdef CONFIG_MTD_NAND_OMAP_PREFETCH > >> >> >> +#define CS_NUM_SHIFT 24 > >> >> >> +#define ENABLE_PREFETCH 7 > >> >> >> +#define DMA_MPU_MODE 2 > >> >> >> +#endif > >> >> >> + > >> >> >> static struct resource gpmc_mem_root; > >> >> >> static struct resource gpmc_cs_mem[GPMC_CS_NUM]; > >> >> >> static DEFINE_SPINLOCK(gpmc_mem_lock); > >> >> >> @@ -383,6 +389,99 @@ void gpmc_cs_free(int cs) > >> >> >> } > >> >> >> EXPORT_SYMBOL(gpmc_cs_free); > >> >> >> > >> >> >> +#ifdef CONFIG_MTD_NAND_OMAP_PREFETCH > >> >> >> +/** > >> >> >> + * gpmc_prefetch_init - configures default configuration for > >> >> >> prefetch > >> engine > >> >> >> + */ > >> >> >> +static void gpmc_prefetch_init(void) > >> >> >> +{ > >> >> >> + /* Setting the default threshold to 64 */ > >> >> >> + gpmc_write_reg(GPMC_PREFETCH_CONTROL, 0x0); > >> >> >> + gpmc_write_reg(GPMC_PREFETCH_CONFIG1, 0x40 << 8); > >> >> >> + gpmc_write_reg(GPMC_PREFETCH_CONFIG2, 0x0); > >> >> >> +} > >> >> > > >> >> > Why would you want to have NAND specific init code int gpmc.c? > >> >> > > >> >> > The purpose if gpmc.c is to provide access to configuring the > >> >> > General Purpose Memory Controller (GPMC). You should just provide > >> >> > functions in gpmc.c for the platform init code to use, and then > >> >> > the drivers can stay platform independent. > >> >> > >> >> In my understanding, this 'prefetch' engine is part of GPMC itself, it > >> >> is a > >> >> kind of feature provided by GPMC which can be utilized by NAND driver. > >> >> So, to me, it makes sens to get initialized prefetch by GPMC itself so > >> >> that > >> >> NAND driver can use it. > >> > > >> > But it should not have a dependency to NAND. > >> > >> This engine, in GPMC, is dedicated for NAND devices only. > >> > >> > > >> >> Another reason was that all read / write to GPMC register are done by > >> >> functions 'gpmc_read_reg' / 'gpmc_write_reg', which have been made > >> >> 'static' in nature. > >> > > >> > That's why you need to provide a generic function in gpmc.c to enable > >> > prefetch that the platform code for any driver can use. > >> > >> Exactly, and whenever a platform code uses gpmc init call, gpmc initializes > >> this engine too. Since prefetch engine is the part of GPMC, IMHOP, it > >> should > >> get initialized as part of GPMC initialization. > > > > No, the driver needing it should initialize it. There should not be any > > ifdefs needed in the gpmc.c for that. > > Are you suggesting to move gpmc prefetch specific code to > 'drivers/mtd/nand/omap2.c'? > This can be done but then, we will be accessing gpmc registers outside > gpmc.c. Is that ok?
Well I'm thinking that you just basically need something like this in gpmc.c: int gpmc_prefetch_request(int cs); int gpmc_prefetch_enable(int cs); int gpmc_prefetch_reset(int cs); ... And gpmc_prefetch_request would then return an error if already taken. No need then to tinker with the GPMC prefetch registers in the NAND driver. > > > >> And then there are prefetch start, stop and status functions calls have > >> been > >> provided to be used by NAND driver. > > > > These should really be done in the platform init code for the NAND driver. > > The NAND driver really should be generic, not omap specific. > > Are you talking about different omap versions or omap itself, I am bit > confused. This NAND driver is > omap specific only. I guess I'm talking in generic terms. What's under drivers/* should in the long run be device independent code, and the platform specific code should be under arch/arm/*omap*. Regards, Tony -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
