From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Jeffery Date: Tue, 29 Aug 2017 16:26:49 +0930 Subject: [PATCH] i2c: aspeed: Retain delay/setup/hold values when configuring bus frequency In-Reply-To: <20170828160702.x45hagij4kkm5zzc@ninjato> References: <20170815072102.23067-1-andrew@aj.id.au> <20170828160702.x45hagij4kkm5zzc@ninjato> Message-ID: <1503989809.5933.5.camel@aj.id.au> List-Id: To: linux-aspeed@lists.ozlabs.org MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit On Mon, 2017-08-28 at 18:07 +0200, Wolfram Sang wrote: > On Tue, Aug 15, 2017 at 04:51:02PM +0930, Andrew Jeffery wrote: > > In addition to the base, low and high clock configuration, the AC timing > > register #1 on the AST2400 houses fields controlling: > > > > 1. tBUF: Minimum delay between Stop and Start conditions > > 2. tHDSTA: Hold time for the Start condition > > 3. tACST: Setup time for Start and Stop conditions, and hold time for the > >    Repeated Start condition > > > > These values are defined in hardware on the AST2500 and therefore don't > > need to be set. > > > > aspeed_i2c_init_clk() was performing a direct write of the generated > > clock values rather than a read/mask/modify/update sequence to retain > > tBUF, tHDSTA and tACST, and therefore cleared the tBUF, tHDSTA and tACST > > fields on the AST2400. This resulted in a delay/setup/hold time of 1 > > base clock, which in some configurations is not enough for some devices > > (e.g. the MAX31785 fan controller, with an APB of 48MHz and a desired > > bus speed of 100kHz). > > > > Signed-off-by: Andrew Jeffery > > Applied to for-next, thanks! Thanks! > I even considered for-current but it does > not apply there. So, I leave the backporting for the interested parties > :) > It depends on Brendan's clock divisor calculation fix, which appears to be in for-next but not for-current: 87b59ff8d1d9 i2c: aspeed: add proper support fo 24xx clock params I'd argue that Brendan's patch should go in for-current as well, because it fixes a divisor rounding error for the ast2500 (bus is clocked faster than requested). Cheers, Andrew -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 801 bytes Desc: This is a digitally signed message part URL: