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From: Marek Szyprowski <m.szyprowski@samsung.com>
To: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>,
	Bjorn Helgaas <helgaas@kernel.org>,
	Jaehoon Chung <jh80.chung@samsung.com>,
	Jingoo Han <jingoohan1@gmail.com>
Cc: "Krzysztof Wilczyński" <kw@linux.com>,
	"Alim Akhtar" <alim.akhtar@samsung.com>,
	linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-samsung-soc@vger.kernel.org
Subject: Re: pci-exynos.c phy_init() usage
Date: Mon, 27 Jun 2022 12:30:18 +0200	[thread overview]
Message-ID: <591f696f-b55c-d267-7fcb-74f7fd4a6900@samsung.com> (raw)
In-Reply-To: <c0c802c0-82e1-e7bb-48be-974ac23b5a15@linaro.org>

Hi,

On 24.06.2022 20:07, Krzysztof Kozlowski wrote:
> On 24/06/2022 19:35, Bjorn Helgaas wrote:
>> In exynos_pcie_host_init() [1], we call:
>>
>>    phy_reset(ep->phy);
>>    phy_power_on(ep->phy);
>>    phy_init(ep->phy);
>>
>> The phy_init() function comment [2] says it must be called before
>> phy_power_on().  Is exynos doing this backwards?
> Looks like. I don't have Exynos hardware with a PCI, so cannot
> test/fix/verify.
>
> Luckily for Exynos ;-) it's not alone in this pattern:
> drivers/net/ethernet/marvell/sky2.c
> drivers/usb/dwc2/platform.c

I've checked that on the real hardware. Swapping the order of 
phy_power_on and phy_init breaks driver operation.

However pci-exynos is the only driver that uses the phy-exynos-pcie, so 
we can simply swap the content of the init and power_on in the phy 
driver to adjust the code to the right order. power_on/init and 
exit/power_off are also called one after the other in pci-exynos, 
without any activity between them, so we can also simply move all 
operation to one pair of the callback, like power_on/off.

Krzysztof, which solution would you prefer?

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland


WARNING: multiple messages have this Message-ID (diff)
From: Marek Szyprowski <m.szyprowski@samsung.com>
To: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>,
	Bjorn Helgaas <helgaas@kernel.org>,
	Jaehoon Chung <jh80.chung@samsung.com>,
	Jingoo Han <jingoohan1@gmail.com>
Cc: "Krzysztof Wilczyński" <kw@linux.com>,
	"Alim Akhtar" <alim.akhtar@samsung.com>,
	linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-samsung-soc@vger.kernel.org
Subject: Re: pci-exynos.c phy_init() usage
Date: Mon, 27 Jun 2022 12:30:18 +0200	[thread overview]
Message-ID: <591f696f-b55c-d267-7fcb-74f7fd4a6900@samsung.com> (raw)
In-Reply-To: <c0c802c0-82e1-e7bb-48be-974ac23b5a15@linaro.org>

Hi,

On 24.06.2022 20:07, Krzysztof Kozlowski wrote:
> On 24/06/2022 19:35, Bjorn Helgaas wrote:
>> In exynos_pcie_host_init() [1], we call:
>>
>>    phy_reset(ep->phy);
>>    phy_power_on(ep->phy);
>>    phy_init(ep->phy);
>>
>> The phy_init() function comment [2] says it must be called before
>> phy_power_on().  Is exynos doing this backwards?
> Looks like. I don't have Exynos hardware with a PCI, so cannot
> test/fix/verify.
>
> Luckily for Exynos ;-) it's not alone in this pattern:
> drivers/net/ethernet/marvell/sky2.c
> drivers/usb/dwc2/platform.c

I've checked that on the real hardware. Swapping the order of 
phy_power_on and phy_init breaks driver operation.

However pci-exynos is the only driver that uses the phy-exynos-pcie, so 
we can simply swap the content of the init and power_on in the phy 
driver to adjust the code to the right order. power_on/init and 
exit/power_off are also called one after the other in pci-exynos, 
without any activity between them, so we can also simply move all 
operation to one pair of the callback, like power_on/off.

Krzysztof, which solution would you prefer?

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland


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  reply	other threads:[~2022-06-27 10:30 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-06-24 17:35 pci-exynos.c phy_init() usage Bjorn Helgaas
2022-06-24 17:35 ` Bjorn Helgaas
2022-06-24 18:07 ` Krzysztof Kozlowski
2022-06-24 18:07   ` Krzysztof Kozlowski
2022-06-27 10:30   ` Marek Szyprowski [this message]
2022-06-27 10:30     ` Marek Szyprowski
2022-06-27 10:47     ` Krzysztof Kozlowski
2022-06-27 10:47       ` Krzysztof Kozlowski
2022-06-28  8:13       ` Marek Szyprowski
2022-06-28  8:13         ` Marek Szyprowski
2022-06-28  8:27         ` Krzysztof Kozlowski
2022-06-28  8:27           ` Krzysztof Kozlowski
2022-06-28 10:59           ` Bjorn Helgaas
2022-06-28 10:59             ` Bjorn Helgaas

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