Re: PATCH: rtsx_pci driver - don't disable the rts5229 card reader on Intel NUC boxes

From: Chris Clayton <chris2553@googlemail.com>
To: "吳昊澄 Ricky" <ricky_wu@realtek.com>,
	"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
	"rdunlap@infradead.org" <rdunlap@infradead.org>,
	"philquadra@gmail.com" <philquadra@gmail.com>,
	Arnd Bergmann <arnd@arndb.de>
Subject: Re: PATCH: rtsx_pci driver - don't disable the rts5229 card reader on Intel NUC boxes
Date: Tue, 4 Aug 2020 09:50:45 +0100	[thread overview]
Message-ID: <0afbd711-0bda-d9a3-138d-5c713b4e2ed9@googlemail.com> (raw)
In-Reply-To: <11e224ca299b48f1bea07082f2ff7c00@realtek.com>

On 04/08/2020 09:08, 吳昊澄 Ricky wrote:
>> -----Original Message-----
>> From: gregkh@linuxfoundation.org [mailto:gregkh@linuxfoundation.org]
>> Sent: Tuesday, August 04, 2020 3:49 PM
>> To: 吳昊澄 Ricky
>> Cc: Chris Clayton; LKML; rdunlap@infradead.org; philquadra@gmail.com; Arnd
>> Bergmann
>> Subject: Re: PATCH: rtsx_pci driver - don't disable the rts5229 card reader on
>> Intel NUC boxes
>>
>> On Tue, Aug 04, 2020 at 02:44:41AM +0000, 吳昊澄 Ricky wrote:
>>> Hi Chris,
>>>
>>> rtsx_pci_write_register(pcr, FPDTL, OC_POWER_DOWN, OC_POWER_DOWN);
>>> This register operation saved power under 1mA, so if do not care the 1mA
>> power we can have a patch to remove it, make compatible with NUC6
>>> We tested others our card reader that remove it, we did not see any side effect
>>>
>>> Hi Greg k-h,
>>>
>>> Do you have any comments?
>>
>> comments on what?  I don't know what you are responding to here, sorry.
>>
> Can we have a patch to kernel for NUC6? It may cause more power(1mA) but it will have more compatibility
> 

Ricky,

I don't understand why you want to completely remove the code that sets up the 1mA power saving. That code was there
even before your patch (bede03a579b3b4a036003c4862cc1baa4ddc351f), so I assume it benefits some of the Realtek card
readers. Before your patch however, rtsx_pci_init_ocp() was not called for the rts5229 reader, but the patch introduced
an unconditional call to that function into rtsx_pci_init_hw(), which is run for the rts5229. That is what now disables
the card reader.

Now, I don't know whether other cards are affected, although I don't recall seeing any reported as I searched the kernel
and ubuntu bugzillas for any analysis of the problem. I know this is not what the patch I sent does, but having thought
about it more, seems to me that the simplest fix is to skip the new call to rtsx_pci_init_ocp() if the reader is an rts5229.

If you agree, I can prepare a patch and send it to you. Whatever the solution is, it will also be needed in the stable
kernels later than 5.0.

Chris
>> greg k-h
>>
>> ------Please consider the environment before printing this e-mail.