OMAP: Fix for bus width which improves SD card's peformance.
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From: Felipe Balbi on 5 Apr 2010 12:50 Hi, On Mon, Apr 05, 2010 at 06:26:16PM +0530, kishore kadiyala wrote: > @@ -2091,9 +2091,9 @@ static int __init omap_hsmmc_probe(struct > mmc->caps |= MMC_CAP_MMC_HIGHSPEED | MMC_CAP_SD_HIGHSPEED | > MMC_CAP_WAIT_WHILE_BUSY; > > - if (mmc_slot(host).wires >= 8) > - mmc->caps |= MMC_CAP_8_BIT_DATA; > - else if (mmc_slot(host).wires >= 4) > + if (mmc_slot(host).wires == 8) > + mmc->caps |= (MMC_CAP_8_BIT_DATA | MMC_CAP_4_BIT_DATA); > + else if (mmc_slot(host).wires == 4) > mmc->caps |= MMC_CAP_4_BIT_DATA; I believe it would be enough to just remove the 'else', so the code would look like: if (mmc_slot(host).wires >= 8) mmc->caps |= MMC_CAP_8_BIT_DATA; if (mmc_slot(host).wires >= 4) mmc->caps |= MMC_CAP_4_BIT_DATA; -- balbi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Felipe Balbi on 6 Apr 2010 01:10 Hi, On Mon, Apr 05, 2010 at 12:19:29PM -0500, Madhusudhan wrote: > Since the first if command already checks for the 8-bit the second check > like >= 4 is definitely not readable in my opinion. how come ??? > Functionally do you see anything wrong with this patch?? functionally no, but (hypothetical situation) and if on omap4/5/6/whatever, omap controller supports a bigger bus width then you'll have to add a line like: + if (mmc_slot(host).wires == 16) + mmc->caps |= (MMC_CAP_16_BIT_DATA | MMC_CAP_8_BIT_DATA | + MMC_CAP_4_BIT_DATA); - if (mmc_slot(host).wires == 8) + else if (mmc_slot(host).wires == 8) do you see the problem ?? In my opinion it doesn't scale well. -- balbi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Felipe Balbi on 6 Apr 2010 12:40 On Tue, Apr 06, 2010 at 06:16:01PM +0200, ext Madhusudhan wrote: > > >> -----Original Message----- >> From: Felipe Balbi [mailto:me(a)felipebalbi.com] >> Sent: Tuesday, April 06, 2010 12:01 AM >> To: Madhusudhan >> Cc: me(a)felipebalbi.com; 'kishore kadiyala'; 'Vimal Singh'; >> tony(a)atomide.com; svenkatr(a)ti.com; linux-omap(a)vger.kernel.org; linux- >> kernel(a)vger.kernel.org; jarkko.lavinen(a)nokia.com >> Subject: Re: [PATCH v3] OMAP: Fix for bus width which improves SD card's >> peformance. >> >> Hi, >> >> On Mon, Apr 05, 2010 at 12:19:29PM -0500, Madhusudhan wrote: >> > Since the first if command already checks for the 8-bit the second check >> > like >= 4 is definitely not readable in my opinion. >> >> how come ??? >> >> > Functionally do you see anything wrong with this patch?? >> >> functionally no, but (hypothetical situation) and if on >> omap4/5/6/whatever, omap controller supports a bigger bus width then >> you'll have to add a line like: >> >> + if (mmc_slot(host).wires == 16) >> + mmc->caps |= (MMC_CAP_16_BIT_DATA | MMC_CAP_8_BIT_DATA | >> + MMC_CAP_4_BIT_DATA); >> - if (mmc_slot(host).wires == 8) >> + else if (mmc_slot(host).wires == 8) >> >> do you see the problem ?? In my opinion it doesn't scale well. >> > >The point we should note here is that MMC spec supports a max bus width of >8-bit. So anything beyond 8-bit is not in the picture as of today. in that case, the code could be: WARN_ON(mmc_slot(host).wires > 8); if (mmc_slot(host).wires == 8) mmc->caps |= MMC_CAP_8_BIT_DATA; if (mmc_slot(host).wires >= 4) mmc->caps |= MMC_CAP_4_BIT_DATA; -- balbi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Felipe Balbi on 6 Apr 2010 13:00
On Tue, Apr 06, 2010 at 06:55:03PM +0200, ext Nishanth Menon wrote: >some reasons why i love switch statements ;) since I dont expect other >than precisely 4 and 8 (do we expect 5,6,7 - i might be wrong).. but if >it is so, wont the following be better? > >switch (mmc_slot(host).wires) >{ >case 8: > mmc->caps |= MMC_CAP_8_BIT_DATA; > /* fall thru*/ >case 4: > mmc->caps |= MMC_CAP_4_BIT_DATA; > break; >default: > WARN("bad width"); >} I like that, but I remember Madhu (or someone else) saying he thinks it's less readable this way. Go figure... -- balbi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |