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From: Doug Anderson <dianders@chromium.org>
To: Maulik Shah <mkshah@codeaurora.org>
Cc: Andy Gross <agross@kernel.org>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Rajendra Nayak <rnayak@codeaurora.org>,
	Matthias Kaehlcke <mka@chromium.org>,
	Evan Green <evgreen@chromium.org>,
	Stephen Boyd <swboyd@chromium.org>,
	Lina Iyer <ilina@codeaurora.org>,
	linux-arm-msm <linux-arm-msm@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [RFT PATCH 2/9] drivers: qcom: rpmh-rsc: Document the register layout better
Date: Wed, 11 Mar 2020 08:27:44 -0700	[thread overview]
Message-ID: <CAD=FV=W5RGwu=ywtM7aCv3H-EpJ1i23S0awgVc8QtOsXtige4w@mail.gmail.com> (raw)
In-Reply-To: <285d3315-7558-d9f6-fe65-24d8ad07949d@codeaurora.org>

Hi,

On Wed, Mar 11, 2020 at 2:35 AM Maulik Shah <mkshah@codeaurora.org> wrote:
>
> Hi Doug,
>
> On 3/7/2020 5:29 AM, Douglas Anderson wrote:
> > Perhaps it's just me, it took a really long time to understand what
> > the register layout of rpmh-rsc was just from the #defines.
> i don't understand why register layout is so important for you to understand?
>
> besides, i think all required registers are properly named with #define
>
> for e.g.
> /* Register offsets */
> #define RSC_DRV_IRQ_ENABLE              0x00
> #define RSC_DRV_IRQ_STATUS              0x04
> #define RSC_DRV_IRQ_CLEAR               0x08
>
> now when you want to enable/disable irq in driver code, its pretty simple to figure out
> that we need to read/write at RSC_DRV_IRQ_ENABLE offset.

It's not the specific layout that's important to me.  It's the
relationships between everything.  In other words:

a) one rpmh-rsc contains some registers and then a whole bunch of TCS blocks

b) one TCS block contains some registers and space for up to 16 commands.

c) each command has a handful of registers

Nothing describes this in the existing code--you've gotta read through
all the code and figure out how it's reading/writing registers to
figure it out.


> this seems unnecessary change to me, can you please drop this when you spin v2?

In v2 I'll replace this with the prose below.  Personally I find this
inferior to the struct definitions which are easier to read
at-a-glance, but it seems like it would be less controversial...

/*
 * Here's a high level overview of how all the registers in RPMH work
 * together:
 *
 * - The main rpmh-rsc address is the base of a register space that can
 *   be used to find overall configuration of the hardware
 *   (DRV_PRNT_CHLD_CONFIG).  Also found within the rpmh-rsc register
 *   space are all the TCS blocks.  The offset of the TCS blocks is
 *   specified in the device tree by "qcom,tcs-offset" and used to
 *   compute tcs_base.
 * - TCS blocks come one after another.  Type, count, and order are
 *   specified by the device tree as "qcom,tcs-config".
 * - Each TCS block has some registers, then space for up to 16 commands.
 *   Note that though address space is reserved for 16 commands, fewer
 *   might be present.  See ncpt (num cmds per TCS).
 * - The first TCS block is special in that it has registers to control
 *   interrupts (RSC_DRV_IRQ_XXX).  Space for these registers is reserved
 *   in all TCS blocks to make the math easier, but only the first one
 *   matters.
 */

I'll also move the documentation of "irq_clear", "cmd_wait_for_cmpl",
"status", and "cmd_enable" next to the respective #defines.


  reply	other threads:[~2020-03-11 15:28 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-06 23:59 [RFT PATCH 0/9] drivers: qcom: rpmh-rsc: Cleanup / add lots of comments Douglas Anderson
2020-03-06 23:59 ` [RFT PATCH 1/9] drivers: qcom: rpmh-rsc: Clean code reading/writing regs/cmds Douglas Anderson
2020-03-11  8:47   ` Maulik Shah
2020-03-11 15:03     ` Doug Anderson
2020-03-11 16:17       ` Matthias Kaehlcke
2020-03-11 19:30         ` Stephen Boyd
2020-03-06 23:59 ` [RFT PATCH 2/9] drivers: qcom: rpmh-rsc: Document the register layout better Douglas Anderson
2020-03-11  9:35   ` Maulik Shah
2020-03-11 15:27     ` Doug Anderson [this message]
2020-03-11 18:49       ` Evan Green
2020-03-11 20:08       ` Stephen Boyd
2020-03-11 22:35         ` Doug Anderson
2020-03-06 23:59 ` [RFT PATCH 3/9] drivers: qcom: rpmh-rsc: Fold tcs_ctrl_write() into its single caller Douglas Anderson
2020-03-11  9:50   ` Maulik Shah
2020-03-06 23:59 ` [RFT PATCH 4/9] drivers: qcom: rpmh-rsc: Remove get_tcs_of_type() abstraction Douglas Anderson
2020-03-11 12:02   ` Maulik Shah
2020-03-06 23:59 ` [RFT PATCH 5/9] drivers: qcom: rpmh-rsc: A lot of comments Douglas Anderson
2020-03-06 23:59 ` [RFT PATCH 6/9] drivers: qcom: rpmh-rsc: Only use "tcs_in_use" for ACTIVE_ONLY Douglas Anderson
2020-03-11  0:33   ` Doug Anderson
2020-03-06 23:59 ` [RFT PATCH 7/9] drivers: qcom: rpmh-rsc: Warning if tcs_write() used for non-active Douglas Anderson
2020-03-06 23:59 ` [RFT PATCH 8/9] drivers: qcom: rpmh-rsc: spin_lock_irqsave() for tcs_invalidate() Douglas Anderson
2020-03-06 23:59 ` [RFT PATCH 9/9] drivers: qcom: rpmh-rsc: Kill cmd_cache and find_match() with fire Douglas Anderson
2020-03-11  0:35   ` Doug Anderson
2020-03-11  9:48 ` [RFT PATCH 0/9] drivers: qcom: rpmh-rsc: Cleanup / add lots of comments Maulik Shah

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