Re: [PATCH v3 5/5] mmc: sdhci-of-aspeed: Assert/Deassert reset signal before probing eMMC
From: Philipp Zabel <p.zabel@pengutronix.de>
Date: 2021-05-06 10:25:34
Also in:
linux-arm-kernel, linux-aspeed, linux-mmc, lkml, openbmc
Hi Steven, On Thu, May 06, 2021 at 06:03:12PM +0800, Steven Lee wrote:
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For cleaning up the AST2600 eMMC controller, the reset signal should be asserted and deasserted before it is probed. Signed-off-by: Steven Lee <redacted> --- 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
[...]
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@@ -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:
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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().
+ 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?
+ 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?
+ } + } + } + 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. regards Philipp