From: Steven Lee <steven_lee@aspeedtech.com>
To: Philipp Zabel <p.zabel@pengutronix.de>
Cc: Andrew Jeffery <andrew@aj.id.au>,
Ulf Hansson <ulf.hansson@linaro.org>,
Rob Herring <robh+dt@kernel.org>, Joel Stanley <joel@jms.id.au>,
"Adrian Hunter" <adrian.hunter@intel.com>,
Ryan Chen <ryanchen.aspeed@gmail.com>,
"moderated list:ASPEED SD/MMC DRIVER"
<linux-aspeed@lists.ozlabs.org>,
"moderated list:ASPEED SD/MMC DRIVER" <openbmc@lists.ozlabs.org>,
"open list:ASPEED SD/MMC DRIVER" <linux-mmc@vger.kernel.org>,
"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
<devicetree@vger.kernel.org>,
"moderated list:ARM/ASPEED MACHINE SUPPORT"
<linux-arm-kernel@lists.infradead.org>,
open list <linux-kernel@vger.kernel.org>,
"Hongweiz@ami.com" <Hongweiz@ami.com>,
"Ryan Chen" <ryan_chen@aspeedtech.com>,
Chin-Ting Kuo <chin-ting_kuo@aspeedtech.com>
Subject: Re: [PATCH v3 5/5] mmc: sdhci-of-aspeed: Assert/Deassert reset signal before probing eMMC
Date: Fri, 7 May 2021 14:02:29 +0800 [thread overview]
Message-ID: <20210507060228.GC23749@aspeedtech.com> (raw)
In-Reply-To: <20210506102458.GA20777@pengutronix.de>
The 05/06/2021 18:24, Philipp Zabel wrote:
> Hi Steven,
>
> On Thu, May 06, 2021 at 06:03:12PM +0800, Steven Lee wrote:
> > For cleaning up the AST2600 eMMC controller, the reset signal should be
> > asserted and deasserted before it is probed.
> >
> > Signed-off-by: Steven Lee <steven_lee@aspeedtech.com>
> > ---
> > drivers/mmc/host/sdhci-of-aspeed.c | 49 ++++++++++++++++++++++++------
> > 1 file changed, 40 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/mmc/host/sdhci-of-aspeed.c b/drivers/mmc/host/sdhci-of-aspeed.c
> > index 4979f98ffb52..8ef06f32abff 100644
> > --- a/drivers/mmc/host/sdhci-of-aspeed.c
> > +++ b/drivers/mmc/host/sdhci-of-aspeed.c
> [...]
> > @@ -533,11 +545,22 @@ static struct platform_driver aspeed_sdhci_driver = {
> > .remove = aspeed_sdhci_remove,
> > };
> >
> > +static const struct of_device_id aspeed_sdc_of_match[] = {
> > + { .compatible = "aspeed,ast2400-sd-controller", },
> > + { .compatible = "aspeed,ast2500-sd-controller", },
> > + { .compatible = "aspeed,ast2600-sd-controller", .data = &ast2600_sdc_info},
> > + { }
> > +};
> > +
> > +MODULE_DEVICE_TABLE(of, aspeed_sdc_of_match);
> > +
> > static int aspeed_sdc_probe(struct platform_device *pdev)
> >
> > {
> > struct device_node *parent, *child;
> > struct aspeed_sdc *sdc;
> > + const struct of_device_id *match = NULL;
> > + const struct aspeed_sdc_info *info = NULL;
>
> There is no need to initialize these variables to NULL, see below:
>
Will modify it.
> > int ret;
> >
> > sdc = devm_kzalloc(&pdev->dev, sizeof(*sdc), GFP_KERNEL);
> > @@ -546,6 +569,23 @@ static int aspeed_sdc_probe(struct platform_device *pdev)
> >
> > spin_lock_init(&sdc->lock);
> >
> > + match = of_match_device(aspeed_sdc_of_match, &pdev->dev);
>
> match is set unconditionally before it is used,
>
> > + if (!match)
> > + return -ENODEV;
> > +
> > + if (match->data)
> > + info = match->data;
>
> and info could be set unconditionally as well:
>
> info = match->data;
>
> > + if (info) {
> > + if (info->flag & PROBE_AFTER_ASSET_DEASSERT) {
> > + sdc->rst = devm_reset_control_get(&pdev->dev, NULL);
>
> Please use devm_reset_control_get_exclusive() or
> devm_reset_control_get_optional_exclusive().
>
Will modify as you suggest.
> > + if (!IS_ERR(sdc->rst)) {
>
> Please just return errors here instead of ignoring them.
> The reset_control_get_optional variants return NULL in case the
> device node doesn't contain a resets phandle, in case you really
> consider this reset to be optional even though the flag is set?
>
Will return error here.
> > + reset_control_assert(sdc->rst);
> > + reset_control_deassert(sdc->rst);
>
> Is there no need for delays between assertion and deassertion or after
> the reset is deasserted?
>
Per the internal discussion, I Will add udelay(1).
> > + }
> > + }
> > + }
> > +
> > sdc->clk = devm_clk_get(&pdev->dev, NULL);
> > if (IS_ERR(sdc->clk))
> > return PTR_ERR(sdc->clk);
>
> In general, I would assert/deassert the reset only after all resources
> are successfully acquired. This might avoid unnecessary resets in case
> of probe deferrals.
>
Thanks for the suggestion. I will try to move the implementation of
reset after devm_ioremap_resource().
> regards
> Philipp
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prev parent reply other threads:[~2021-05-07 6:05 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-06 10:03 [PATCH v3 0/5] mmc: sdhci-of-aspeed: Support toggling SD bus signal Steven Lee
2021-05-06 10:03 ` [PATCH v3 1/5] dt-bindings: mmc: sdhci-of-aspeed: Add an example for AST2600-A2 EVB Steven Lee
2021-05-07 1:13 ` Rob Herring
2021-05-07 3:13 ` Steven Lee
2021-05-07 17:21 ` Rob Herring
2021-05-10 2:32 ` Steven Lee
2021-05-06 10:03 ` [PATCH v3 2/5] ARM: dts: aspeed: ast2600evb: Add comment for gpio regulator of sdhci Steven Lee
2021-05-07 1:40 ` Andrew Jeffery
2021-05-07 3:30 ` Steven Lee
2021-05-07 3:42 ` Andrew Jeffery
2021-05-06 10:03 ` [PATCH v3 3/5] ARM: dts: aspeed: ast2600evb: Add phase correction for emmc controller Steven Lee
2021-05-07 1:34 ` Andrew Jeffery
2021-05-06 10:03 ` [PATCH v3 4/5] mmc: sdhci-of-aspeed: Add a helper for updating capability register Steven Lee
2021-05-07 2:13 ` Andrew Jeffery
2021-05-07 6:59 ` Steven Lee
2021-05-07 7:07 ` Andrew Jeffery
2021-05-06 10:03 ` [PATCH v3 5/5] mmc: sdhci-of-aspeed: Assert/Deassert reset signal before probing eMMC Steven Lee
2021-05-06 10:24 ` Philipp Zabel
2021-05-07 1:32 ` Andrew Jeffery
2021-05-07 6:24 ` Steven Lee
2021-05-07 7:36 ` Andrew Jeffery
2021-05-10 6:03 ` Steven Lee
2021-05-13 0:42 ` Andrew Jeffery
2021-05-14 2:09 ` Steven Lee
2021-05-14 2:37 ` Andrew Jeffery
2021-05-19 10:57 ` Steven Lee
2021-05-19 23:09 ` Andrew Jeffery
2021-05-07 6:02 ` Steven Lee [this message]
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