On Thu, May 20, 2010 at 11:08 AM, Ghorai, Sukumar <s-ghorai@xxxxxx> wrote: > Vimal, > >> -----Original Message----- >> From: Vimal Singh [mailto:vimal.newwork@xxxxxxxxx] >> Sent: 2010-05-20 00:01 >> To: Ghorai, Sukumar >> Cc: linux-omap@xxxxxxxxxxxxxxx; linux-mtd@xxxxxxxxxxxxxxxxxxx; >> tony@xxxxxxxxxxx; sakoman@xxxxxxxxx; mike@xxxxxxxxxxxxxx; >> Artem.Bityutskiy@xxxxxxxxx; peter.barada@xxxxxxxxx >> Subject: Re: [PATCH v3 1/3] omap3 gpmc: functionality enhancement >> >> On Wed, May 19, 2010 at 11:34 PM, Ghorai, Sukumar <s-ghorai@xxxxxx> wrote: >> >> > > + >> >> > > + case GPMC_CONFIG_RDY_BSY: >> >> > > + regval = gpmc_cs_read_reg(cs, GPMC_CS_CONFIG1); >> >> > > + regval |= WR_RD_PIN_MONITORING; >> >> > > + gpmc_cs_write_reg(cs, GPMC_CS_CONFIG1, regval); >> >> > > + break; >> >> > >> >> > IIRC, at least in OMAP2/3, ready/busy pin is not in use (not >> connected). >> >> >> >> On the Logic OMAP3530 LV SOM and Torpedo modules, the R/B# pin of the >> >> NAND in the Micron mt29c2g4maklajg-6it POP part is connected to the >> >> WAIT0 pin on the OMAP3530 and I'm looking to use it to speed up NAND >> >> accesses >> > [Ghorai] So better keep this feature, >> >> Yes, looks like there are some boards which can still take advantage of >> this. >> >> >> >> [...] >> >> > > @@ -456,13 +572,20 @@ EXPORT_SYMBOL(gpmc_prefetch_enable); >> >> > > /** >> >> > > * gpmc_prefetch_reset - disables and stops the prefetch engine >> >> > > */ >> >> > > -void gpmc_prefetch_reset(void) >> >> > > +int gpmc_prefetch_reset(int cs) >> >> > > { >> >> > > + if (gpmc_pref_used == cs) >> >> > > + gpmc_pref_used = -EINVAL; >> >> > > + else >> >> > > + return -EINVAL; >> >> > > + >> >> > >> >> > This is also not required. As, this function will be called only if >> >> > prefetch was used. >> > [Ghorai] Agree. Can you see this input too? >> > http://www.mail-archive.com/linux-omap@xxxxxxxxxxxxxxx/msg28520.html >> >> Exactly, this is what I am telling here. Enable prefetch engine call >> is already being check for *busy* or not. >> >> > >> [...] >> >> > > +int gpmc_ecc_init(int cs, int ecc_size) >> >> > > +{ >> >> > > + unsigned int val = 0x0; >> >> > > + >> >> > > + /* check if ecc engine already by another cs */ >> >> > > + if (gpmc_ecc_used == -EINVAL) >> >> > > + gpmc_ecc_used = cs; >> >> > > + else >> >> > > + return -EBUSY; >> >> > Here few things need be to consider: >> >> > 1. 'init' is supposed to done once for every instance of driver >> during >> >> probe >> >> > 2. But ECC engine, too, have only one instance at a time, So >> >> > 3. As long as all NAND chip are supposed to use same ECC machenism, >> we >> >> > can go for only one time 'init' for all drivers, perhaps in >> >> > gpmc_nand.c. >> >> > 4. But in case, different instances of driver (or NAND chip) requires >> >> > different ECC machenism (for ex. Hamming or BCH, or even with >> >> > different capabilities of error correction), >> >> > this will no longer vailid. Then rather we should have something like >> >> > 'gpmc_ecc_config' call to configer ECC engine for everytime a driver >> >> > needs it (something like as it is done for prefetch engine). >> > [Ghorai] >> > a. do you think it will reduce the throughput? >> No. But in current implementation it will be called for each instance >> driver. (see my 3rd point) >> >> > b. Moreover I think we will take this as 5th patch as cleanup/ >> improvemnt. >> > c. And how to know that ECC engine is in used other driver should not >> use it? Any bit to know that ecc engine is busy, as we check for prefetch? >> Do not really remember config registers. Perhaps there is no way. >> But I guess you should check into register GPMC_ECC_CONFIG at bit 1. >> This is the bit we are setting to enable ECC calculation, IIRC. >> >> > d. any further input on http://www.mail-archive.com/linux- >> omap@xxxxxxxxxxxxxxx/msg28520.html >> And this what I was suggesting in my point 4. In my example >> 'gpmc_ecc_config' is analogy to 'gpmc_ecc_request'. >> I said *config*, since in such scenario you need to configer HW >> ECCconfig register everytime as well, rather just checking >> availability and enabling. > [Ghorai] still I feel we should not mix this patch with cleanup. And yes if possible this will be the 5th one as cleanup. > 4th one - prefetch cleanup > 5th one - ecc cleanup. > Do you think still missing anything for this patch? As long as you take care of current comments, I do not have any further comment for now. -- Regards, Vimal Singh -- 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
