From: Chunyan Zhang <zhang.lyra@gmail.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Stephen Boyd <sboyd@codeaurora.org>,
Chunyan Zhang <chunyan.zhang@spreadtrum.com>,
Michael Turquette <mturquette@baylibre.com>,
Rob Herring <robh+dt@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
linux-clk <linux-clk@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
Mark Brown <broonie@kernel.org>,
Xiaolong Zhang <xiaolong.zhang@spreadtrum.com>,
Orson Zhai <orson.zhai@spreadtrum.com>,
Geng Ren <geng.ren@spreadtrum.com>,
Ben Li <ben.li@spreadtrum.com>
Subject: Re: [PATCH V1 7/9] clk: sprd: add adjustable pll support
Date: Thu, 22 Jun 2017 20:06:29 +0800 [thread overview]
Message-ID: <CAAfSe-vtAqmiJ-ZuxQde4i7FEo76kkbk-mev_S31i3g3GHwrcQ@mail.gmail.com> (raw)
In-Reply-To: <CAK8P3a1ELg1XcY-QOZn-f6kR9yt-Q6LNLUYEY-BNW-2BaBy6EQ@mail.gmail.com>
Hi Arnd,
On 22 June 2017 at 19:15, Arnd Bergmann <arnd@arndb.de> wrote:
> On Thu, Jun 22, 2017 at 12:17 PM, Chunyan Zhang <zhang.lyra@gmail.com> wrote:
>> On 20 June 2017 at 09:37, Stephen Boyd <sboyd@codeaurora.org> wrote:
>>> On 06/18, Chunyan Zhang wrote:
>
>>>> + kint = DIV_ROUND_CLOSEST(((fvco - refin * nint * CCU_PLL_1M)/10000) *
>>>> + ((mask >> (shift + i)) + 1), refin * 100) << i;
>>>> + cfg[index].val |= (kint << shift) & mask;
>>>> + cfg[index].msk |= mask;
>>>> +
>>>> + ibias_val = pll_get_ibias(fvco, pll->itable);
>>>> +
>>>> + mask = pmask(pll, PLL_IBIAS);
>>>> + index = pindex(pll, PLL_IBIAS);
>>>> + shift = pshift(pll, PLL_IBIAS);
>>>> + cfg[index].val |= ibias_val << shift & mask;
>>>> + cfg[index].msk |= mask;
>>>> +
>>>> + for (i = 0; i < reg_num; i++) {
>>>> + if (cfg[i].msk)
>>>> + ccu_pll_writel(pll, i, cfg[i].val, cfg[i].msk);
>>>> + }
>>>> +
>>>
>>> Are we waiting for the writel() to go through above? If so we
>>> need a readl() of the same register to make sure the write has
>>> completed before delaying.
>>
>> After writing these configuration registers, we have to wait a certain
>> time to make sure the pll has worked as we configured. This depends
>> on other circuit part, so we use udelay rather than reading the same
>> register.
>
> I think you have to do both: normally the writel() is not guaranteed
> to arrive at the device until you read back from an address in the
> same device, so the delay must happen after the readl(), or you won't
> know how long to wait for.
I got it, will add the readl() in the next iterator.
Thanks,
Chunyan
>
> Arnd
next prev parent reply other threads:[~2017-06-22 12:06 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-18 1:58 [PATCH V1 0/9] add clock driver for Spreadtrum platforms Chunyan Zhang
2017-06-18 1:58 ` [PATCH V1 1/9] dt-bindings: Add Spreadtrum CCU binding documentation Chunyan Zhang
2017-06-23 20:05 ` Rob Herring
2017-06-18 1:58 ` [PATCH V1 2/9] clk: sprd: Add common infrastructure Chunyan Zhang
2017-06-20 1:29 ` Stephen Boyd
2017-06-22 10:12 ` Chunyan Zhang
2017-06-18 1:58 ` [PATCH V1 3/9] clk: sprd: add gate clock support Chunyan Zhang
2017-06-20 1:31 ` Stephen Boyd
2017-06-22 10:16 ` Chunyan Zhang
2017-06-30 1:43 ` Stephen Boyd
2017-06-18 1:58 ` [PATCH V1 4/9] clk: sprd: add mux " Chunyan Zhang
2017-06-18 1:58 ` [PATCH V1 5/9] clk: sprd: add divider " Chunyan Zhang
2017-06-18 1:58 ` [PATCH V1 6/9] clk: sprd: add composite " Chunyan Zhang
2017-06-19 0:13 ` kbuild test robot
2017-06-18 1:58 ` [PATCH V1 7/9] clk: sprd: add adjustable pll support Chunyan Zhang
2017-06-20 1:37 ` Stephen Boyd
2017-06-22 10:17 ` Chunyan Zhang
2017-06-22 11:15 ` Arnd Bergmann
2017-06-22 12:06 ` Chunyan Zhang [this message]
2017-06-30 1:44 ` Stephen Boyd
2017-06-30 7:55 ` Chunyan Zhang
2017-06-30 19:22 ` Stephen Boyd
2017-07-03 7:41 ` Chunyan Zhang
2017-06-18 1:58 ` [PATCH V1 8/9] clk: sprd: add clocks support for SC9860 Chunyan Zhang
2017-06-20 1:41 ` Stephen Boyd
2017-06-22 10:21 ` Chunyan Zhang
2017-06-30 1:41 ` Stephen Boyd
2017-06-18 1:58 ` [PATCH V1 9/9] arm64: dts: add ccu " Chunyan Zhang
2017-06-20 1:24 ` Stephen Boyd
2017-06-22 10:24 ` Chunyan Zhang
2017-06-30 0:57 ` Stephen Boyd
2017-06-30 7:37 ` Chunyan Zhang
2017-06-20 1:25 ` [PATCH V1 0/9] add clock driver for Spreadtrum platforms Stephen Boyd
2017-06-22 10:07 ` Chunyan Zhang
2017-06-30 0:45 ` Stephen Boyd
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