linux-kernel - Re: [PATCHv2 4/5] mmc: shdci-bcm2835: add verify for 32-bit back-to-back workaround

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Date:	Wed, 05 Nov 2014 22:01:45 -0700
From:	Stephen Warren <swarren@...dotorg.org>
To:	Scott Branden <sbranden@...adcom.com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Russell King <rmk+kernel@....linux.org.uk>,
	Peter Griffin <peter.griffin@...aro.org>,
	Chris Ball <chris@...ntf.net>,
	Piotr Krol <pietrushnic@...il.com>
CC:	linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
	Joe Perches <joe@...ches.com>,
	linux-rpi-kernel@...ts.infradead.org, Ray Jui <rjui@...adcom.com>,
	bcm-kernel-feedback-list@...adcom.com
Subject: Re: [PATCHv2 4/5] mmc: shdci-bcm2835: add verify for 32-bit back-to-back
 workaround

On 11/05/2014 12:00 AM, Scott Branden wrote:
> On 14-11-04 08:59 PM, Stephen Warren wrote:
>> On 10/30/2014 12:36 AM, Scott Branden wrote:
>>> Add a verify option to driver to print out an error message if a
>>> potential back to back write could cause a clock domain issue.
>>
>>> index f8c450a..11af27f 100644
>>
>>> +#ifdef CONFIG_MMC_SDHCI_BCM2835_VERIFY_WORKAROUND
>>> +    struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
>>> +    struct bcm2835_sdhci_host *bcm2835_host = pltfm_host->priv;
>>> +
>>> +    if (bcm2835_host->previous_reg == reg) {
>>> +        if ((reg != SDHCI_HOST_CONTROL)
>>> +            && (reg != SDHCI_CLOCK_CONTROL)) {
>>
>> The comment in patch 3 says the problem doesn't apply to the data
>> register. Why does this check for these two registers rather than data?
> This Verify workaround patch still a work in progress.  I'm still
> getting more info from the silicon designers on the back-to-back
> register writes that are affect.  The spew of 0x20 or 0x28 or 0x2c
> register writes are all ok locations that don't need to be worked
> around.  This patch needs to be corrected with the proper register rules
> still.

FYI, I applied the series except for this patch, and everything
/appeared/ to work OK for a brief test (boot, log in, reboot). Still,
I'll hold off my Tested-by/acked-by until the comment in patch 3 and the
register list above match, and there's no log spew with everything applied.
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