From: addy ke <addy.ke@rock-chips.com>
To: broonie@kernel.org
Cc: heiko@sntech.de, dianders@chromium.org, grant.likely@linaro.org,
robh+dt@kernel.org, amstan@google.com, sonnyrao@google.com,
linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-rockchip@lists.infradead.org, devicetree@vger.kernel.org,
olof@lixom.net, hj@rock-chips.com, kever.yang@rock-chips.com,
xjq@rock-chips.com, huangtao@rock-chips.com, zyw@rock-chips.com,
yzq@rock-chips.com, zhenfu.fang@rock-chips.com,
cf@rock-chips.com, zhangqing@rock-chips.com, hl@rock-chips.com,
wei.luo@rock-chips.com
Subject: Re: [PATCH 1/2] spi/rockchip: fix bug that case spi can't go as fast as slave request
Date: Thu, 16 Oct 2014 17:58:51 +0800 [thread overview]
Message-ID: <543F96DB.40403@rock-chips.com> (raw)
In-Reply-To: <20141016093410.GB2200@sirena.org.uk>
On 2014/10/16 17:34, Mark Brown wrote:
> On Thu, Oct 16, 2014 at 05:16:02PM +0800, addy ke wrote:
>> On 2014/10/15 21:04, Mark Brown wrote:
>>> On Wed, Oct 15, 2014 at 07:25:49PM +0800, Addy Ke wrote:
>
>>>> + if (WARN_ON(rs->speed > MAX_SCLK_OUT))
>>>> + rs->speed = MAX_SCLK_OUT;
>
>>>> + /* the minimum divsor is 2 */
>>>> + if (rs->max_freq < 2 * rs->speed) {
>>>> + clk_set_rate(rs->spiclk, 2 * rs->speed);
>>>> + rs->max_freq = clk_get_rate(rs->spiclk);
>>>> + }
>
>>> I'll apply this but you should be checking the return code from
>>> clk_set_rate() here, please send a followup patch doing that. It might
>
>> If clk_set_rate return error, do I only put dev_warn here or return error value to spi core?
>
> It'd be better to return an error if we need to set the rate and can't
> do it.
>
>>> also be worth consdering just setting the rate unconditionally here, it
>>> seems like it should make things simpler.
>
>> I think we need.
>> If we set the rate unconditionally here, clk_set_rate() will be executed in each spi transfer.
>
> Is that really such a high cost?
>
Not high cost, but I think if the default spi_clk is enough, we do not need to set spi_clk again.
Maybe we can only set spi_clk as (2 * MAX_SCLK_OUT) in probe().
next prev parent reply other threads:[~2014-10-16 9:58 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-15 11:25 [PATCH 0/2] spi: fix two bugs Addy Ke
2014-10-15 11:25 ` [PATCH 1/2] spi/rockchip: fix bug that case spi can't go as fast as slave request Addy Ke
2014-10-15 13:04 ` Mark Brown
[not found] ` <20141015130452.GD27755-GFdadSzt00ze9xe1eoZjHA@public.gmane.org>
2014-10-16 9:16 ` addy ke
2014-10-16 9:34 ` Mark Brown
2014-10-16 9:58 ` addy ke [this message]
2014-10-16 10:26 ` Mark Brown
2014-10-15 11:26 ` [PATCH 2/2] spi/rockchip: fix bug that cause spi transfer timed out in DMA duplex mode Addy Ke
[not found] ` <1413372378-4309-1-git-send-email-addy.ke-TNX95d0MmH7DzftRWevZcw@public.gmane.org>
2014-10-15 13:05 ` Mark Brown
[not found] ` <20141015130547.GE27755-GFdadSzt00ze9xe1eoZjHA@public.gmane.org>
2014-10-16 9:26 ` addy ke
2014-10-16 9:34 ` Mark Brown
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