From: Tejun Heo <tj@kernel.org>
To: Jassi Brar <jassisinghbrar@gmail.com>
Cc: linux-pci@vger.kernel.org, linux-ide@vger.kernel.org, jgarzik@pobox.com
Subject: Re: SIL24: pcie_set_readrq 4096
Date: Thu, 22 Jul 2010 15:18:37 +0200 [thread overview]
Message-ID: <4C48452D.5070207@kernel.org> (raw)
In-Reply-To: <AANLkTinMJktVl28m-mL8i9N8_Q9V471LV3XsxsZlLIp7@mail.gmail.com>
Hello,
On 07/22/2010 04:47 AM, Jassi Brar wrote:
> After implementing driver for PCIe RC controller of a SOC, I came
> across peculiarity
> while testing SIL3132 directly connected to the root port.
>
> My RC IP is configured for maximum of 256bytes of payload size.
> The sata_sil24 driver unconditionally sets pcie_set_readrq(pdev, 4096)
> for the endpoint
> which apparently works for 'every' other host irrespective of their capacity.
>
> In my case it works only if I change to
> pcie_set_readrq(pdev, 256)
>
> Shouldn't the Linux PCI have provision to allow max_read/payload_size
> not higher than
> the least of max capacities of all agents in the chain ?
>
> I see similar use of pcie_set_readrq(pdev, 4096), so could be I am
> missing something ?
It's been a while since I read pci-e spec but IIUC readrq size and
payload size are independent and if readrq is larger than payload size
it's supposed to complete in multiple steps. I could be wrong tho.
Thanks.
--
tejun
next prev parent reply other threads:[~2010-07-22 13:20 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-07-22 2:47 SIL24: pcie_set_readrq 4096 Jassi Brar
2010-07-22 13:18 ` Tejun Heo [this message]
2010-07-22 14:34 ` Jassi Brar
2010-07-22 20:42 ` Tejun Heo
2010-07-23 5:30 ` Rolf Eike Beer
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