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Tue, 24 Jun 2025 22:34:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1750804454; bh=eK8NMyHuwrl8dXYAwi4q/jdKZLqI0hmkAk2+xKgeAtU=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=ek29q7nUOQfyYabkxpsHoxJFUrxv8u4oxmuC8/lTDIqS7HHcQq3jGJokZybHqykBW GYtNHfN4SeEJu3pKWIJ03BPB50bQ1A81gHel5osuiCrybLmmE/KwsVCdAH732vdDPI R9+hZSTHcyLv++4A7V9qdoIiJFg+b3d6xycUzlve50qiOSVhGG2K7ZA3Fdl/vNwMwA 9t13cQ5CuqKSeXNjcfunzzQHokSH0uiRlFj+XPkahPCeYlm6rXI1YZAZ3Rkvp+hjXb KJPAlk1k+lL33i8KlZUBUKSIYwbjlJhNKvPW2T1ZqJvBj6/8RoBI18cquq3cbaCS27 db55Tm0uixDdg== Date: Tue, 24 Jun 2025 17:34:13 -0500 From: Bjorn Helgaas To: Timothy Pearson Cc: linuxppc-dev , linux-kernel , linux-pci , Madhavan Srinivasan , Michael Ellerman , christophe leroy , Naveen N Rao , Bjorn Helgaas , Shawn Anastasio Subject: Re: [PATCH v2 6/6] pci/hotplug/pnv_php: Enable third attention indicator Message-ID: <20250624223413.GA1550003@bhelgaas> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1469323476.1312174.1750293474949.JavaMail.zimbra@raptorengineeringinc.com> On Wed, Jun 18, 2025 at 07:37:54PM -0500, Timothy Pearson wrote: > ----- Original Message ----- > > From: "Bjorn Helgaas" > > To: "Timothy Pearson" > > Cc: "linuxppc-dev" , "linux-kernel" , "linux-pci" > > , "Madhavan Srinivasan" , "Michael Ellerman" , > > "christophe leroy" , "Naveen N Rao" , "Bjorn Helgaas" > > , "Shawn Anastasio" > > Sent: Wednesday, June 18, 2025 2:01:46 PM > > Subject: Re: [PATCH v2 6/6] pci/hotplug/pnv_php: Enable third attention indicator > > > On Wed, Jun 18, 2025 at 11:58:59AM -0500, Timothy Pearson wrote: > >> state > > > > Weird wrapping of last word of subject to here. > > I'll need to see what's up with my git format-patch setup. Apologies > for that across the multiple series. No worries. If you can figure out how to make your mailer use the normal "On xxx, somebody wrote:" attribution instead of duplicating all those headers, that would be far more useful :) > >> +static int pnv_php_get_raw_indicator_status(struct hotplug_slot *slot, u8 > >> *state) > >> +{ > >> + struct pnv_php_slot *php_slot = to_pnv_php_slot(slot); > >> + struct pci_dev *bridge = php_slot->pdev; > >> + u16 status; > >> + > >> + pcie_capability_read_word(bridge, PCI_EXP_SLTCTL, &status); > >> + *state = (status & (PCI_EXP_SLTCTL_AIC | PCI_EXP_SLTCTL_PIC)) >> 6; > > > > Should be able to do this with FIELD_GET(). > > I used the same overall structure as the pciehp_hpc driver here. Do > you want me to also fix up that driver with FIELD_GET()? Nope, I think it's fine to keep this looking like pciehp for now. If somebody wants to use FIELD_GET() in pciehp, I'd probably be OK with that, but no need for you to open that can of worms. > > Is the PCI_EXP_SLTCTL_PIC part needed? It wasn't there before, commit > > log doesn't mention it, and as far as I can tell, this would be the > > only driver to do that. Most expose only the attention status (0=off, > > 1=on, 2=identify/blink). > > > >> + return 0; > >> +} > >> + > >> + > >> static int pnv_php_get_attention_state(struct hotplug_slot *slot, u8 *state) > >> { > >> struct pnv_php_slot *php_slot = to_pnv_php_slot(slot); > >> > >> + pnv_php_get_raw_indicator_status(slot, &php_slot->attention_state); > > > > This is a change worth noting. Previously we didn't read the AIC > > state from PCI_EXP_SLTCTL at all; we used php_slot->attention_state to > > keep track of whatever had been previously set via > > pnv_php_set_attention_state(). > > > > Now we read the current state from PCI_EXP_SLTCTL. It's not clear > > that php_slot->attention_state is still needed at all. > > It probably isn't. It's unclear why IBM took this path at all, > given pciehp's attention handlers predate pnv-php's by many years. > > > Previously, the user could write any value at all to the sysfs > > "attention" file and then read that same value back. After this > > patch, the user can still write anything, but reads will only return > > values with PCI_EXP_SLTCTL_AIC and PCI_EXP_SLTCTL_PIC. > > > >> *state = php_slot->attention_state; > >> return 0; > >> } > >> @@ -461,7 +474,7 @@ static int pnv_php_set_attention_state(struct hotplug_slot > >> *slot, u8 state) > >> mask = PCI_EXP_SLTCTL_AIC; > >> > >> if (state) > >> - new = PCI_EXP_SLTCTL_ATTN_IND_ON; > >> + new = FIELD_PREP(PCI_EXP_SLTCTL_AIC, state); > > > > This changes the behavior in some cases: > > > > write 0: previously turned indicator off, now writes reserved value > > write 2: previously turned indicator on, now sets to blink > > write 3: previously turned indicator on, now turns it off > > If we're looking at normalizing with pciehp with an eye toward > eventually deprecating / removing pnv-php, I can't think of a better > time to change this behavior. I suspect we're the only major user > of this code path at the moment, with most software expecting to see > pciehp-style handling. Thoughts? I'm OK with changing this, but I do think it would be worth calling out the different behavior in the commit log. Bjorn