Re: [PATCH] mtd: rawnand: gpmi: Fix setting busy timeout setting

From: Miquel Raynal <miquel.raynal@bootlin.com>
To: Sascha Hauer <s.hauer@pengutronix.de>
Cc: linux-mtd@lists.infradead.org, Han Xu <han.xu@nxp.com>,
	kernel@pengutronix.de
Subject: Re: [PATCH] mtd: rawnand: gpmi: Fix setting busy timeout setting
Date: Tue, 14 Jun 2022 10:59:20 +0200	[thread overview]
Message-ID: <20220614105920.1ecab2e0@xps-13> (raw)
In-Reply-To: <20220614083437.GR1615@pengutronix.de>

Hi Sascha,

s.hauer@pengutronix.de wrote on Tue, 14 Jun 2022 10:34:37 +0200:

> On Mon, Jun 13, 2022 at 04:07:38PM +0200, Miquel Raynal wrote:
> > Hi Sascha,
> > 
> > s.hauer@pengutronix.de wrote on Mon, 13 Jun 2022 13:30:30 +0200:
> >   
> > > The DEVICE_BUSY_TIMEOUT value is described in the Reference Manual as:
> > > 
> > > | Timeout waiting for NAND Ready/Busy or ATA IRQ. Used in WAIT_FOR_READY
> > > | mode. This value is the number of GPMI_CLK cycles multiplied by 4096.
> > > 
> > > So instead of multiplying the value in cycles with 4096, we have to
> > > divide it by that value. Use DIV_ROUND_UP to make sure we are on the
> > > safe side, especially when the calculated value in cycles is smaller
> > > than 4096 as typically the case.
> > > 
> > > This bug likely never triggered because any timeout != 0 usually will
> > > do. In my case the busy timeout in cycles was originally calculated as
> > > 2408, which multiplied with 4096 is 0x968000. The lower 16 bits were
> > > taken for the 16 bit wide register field, so the register value was
> > > 0x8000. With 2970bf5a32f0 ("mtd: rawnand: gpmi: fix controller timings
> > > setting") however the value in cycles became 2384, which multiplied
> > > with 4096 is 0x950000. The lower 16 bit are 0x0 now resulting in an
> > > intermediate timeout when reading from NAND.
> > > 
> > > Fixes: b1206122069aa ("mtd: rawnand: gpmi: use core timings instead of an empirical derivation")
> > > Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>  
> > 
> > Shouldn't we add a Cc: stable here?  
> 
> I became a bit ignorant about Cc: stable because everything with the
> keyword "Fix" in the subject seems to end up in stable anyway no matter
> if I want it or not.

Yeah with the AUTOSEL logic many fixes are backported, but I think I've
read GKH complaining that this was not a reason for forgetting the
stable Cc when it was relevant... So I ask for it again now :)

> 
> But right, this one should go into stable, I just resent.
> 
> Sascha
> 
> 

Thanks,
Miquèl

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