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From: Icenowy Zheng <icenowy@aosc.io>
To: Maxime Ripard <maxime.ripard@bootlin.com>
Cc: Rob Herring <robh+dt@kernel.org>, Chen-Yu Tsai <wens@csie.org>,
	Giuseppe Cavallaro <peppe.cavallaro@st.com>,
	Corentin Labbe <clabbe.montjoie@gmail.com>,
	netdev@vger.kernel.org, devicetree@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, linux-sunxi@googlegroups.com
Subject: Re: [PATCH 3/5] net: stmmac: dwmac-sun8i: Allow getting syscon regmap from device
Date: Thu, 12 Apr 2018 23:11:08 +0800	[thread overview]
Message-ID: <A027702A-F3F7-4896-B2B8-E024DA521661@aosc.io> (raw)
In-Reply-To: <20180412145628.iaaeue2imiijwx5d@flea>



于 2018年4月12日 GMT+08:00 下午10:56:28, Maxime Ripard <maxime.ripard@bootlin.com> 写到:
>On Wed, Apr 11, 2018 at 10:16:39PM +0800, Icenowy Zheng wrote:
>> From: Chen-Yu Tsai <wens@csie.org>
>> 
>> On the Allwinner R40 SoC, the "GMAC clock" register is in the CCU
>> address space; on the A64 SoC this register is in the SRAM controller
>> address space, and with a different offset.
>> 
>> To access the register from another device and hide the internal
>> difference between the device, let it register a regmap named
>> "emac-clock". We can then get the device from the phandle, and
>> retrieve the regmap with dev_get_regmap(); in this situation the
>> regmap_field will be set up to access the only register in the
>regmap.
>> 
>> Signed-off-by: Chen-Yu Tsai <wens@csie.org>
>> [Icenowy: change to use regmaps with single register, change commit
>>  message]
>> Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
>> ---
>>  drivers/net/ethernet/stmicro/stmmac/dwmac-sun8i.c | 48
>++++++++++++++++++++++-
>>  1 file changed, 46 insertions(+), 2 deletions(-)
>> 
>> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-sun8i.c
>b/drivers/net/ethernet/stmicro/stmmac/dwmac-sun8i.c
>> index 1037f6c78bca..b61210c0d415 100644
>> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac-sun8i.c
>> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-sun8i.c
>> @@ -85,6 +85,13 @@ const struct reg_field old_syscon_reg_field = {
>>  	.msb = 31,
>>  };
>>  
>> +/* Specially exported regmap which contains only EMAC register */
>> +const struct reg_field single_reg_field = {
>> +	.reg = 0,
>> +	.lsb = 0,
>> +	.msb = 31,
>> +};
>> +
>
>I'm not sure this would be wise. If we ever need some other register
>exported through the regmap, will have to change all the calling sites
>everywhere in the kernel, which will be a pain and will break
>bisectability.

In this situation the register can be exported as another
 regmap. Currently the code will access a regmap with name
"emac-clock" for this register.

>
>Chen-Yu's (or was it yours?) initial solution with a custom writeable
>hook only allowing a single register seemed like a better one.

But I remember you mentioned that you want it to hide the
difference inside the device.

>
>Maxime

  reply	other threads:[~2018-04-12 15:12 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-11 14:16 [PATCH 0/5] Add support in dwmac-sun8i for accessing EMAC clock Icenowy Zheng
2018-04-11 14:16 ` [PATCH 1/5] dt-bindings: allow dwmac-sun8i to use other devices' exported regmap Icenowy Zheng
2018-04-11 14:36   ` [linux-sunxi] " Brüns, Stefan
2018-04-16 18:47   ` Rob Herring
2018-04-16 23:17     ` Icenowy Zheng
2018-04-28 13:42       ` [linux-sunxi] " Chen-Yu Tsai
2018-04-11 14:16 ` [PATCH 2/5] net: stmmac: dwmac-sun8i: Use regmap_field for syscon register access Icenowy Zheng
2018-04-11 14:16 ` [PATCH 3/5] net: stmmac: dwmac-sun8i: Allow getting syscon regmap from device Icenowy Zheng
2018-04-12 14:56   ` Maxime Ripard
2018-04-12 15:11     ` Icenowy Zheng [this message]
2018-04-12 15:23       ` [linux-sunxi] " Chen-Yu Tsai
2018-04-16 14:31         ` Maxime Ripard
2018-04-16 14:34           ` Icenowy Zheng
2018-04-16 14:51           ` Chen-Yu Tsai
2018-04-17 11:52             ` Maxime Ripard
2018-04-17 11:59               ` Chen-Yu Tsai
2018-04-17 12:06                 ` Icenowy Zheng
2018-04-13  6:03   ` [RFC PATCH] net: stmmac: dwmac-sun8i: single_reg_field can be static kbuild test robot
2018-04-13  6:03   ` [PATCH 3/5] net: stmmac: dwmac-sun8i: Allow getting syscon regmap from device kbuild test robot
2018-04-11 14:16 ` [PATCH 4/5] drivers: soc: sunxi: export a regmap for EMAC clock reg on A64 Icenowy Zheng
2018-04-11 14:16 ` [PATCH 5/5] arm64: allwinner: a64: add SRAM controller device tree node Icenowy Zheng
2018-04-12 14:58   ` Maxime Ripard

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