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SubjectRe: [RFT PATCH 1/9] drivers: qcom: rpmh-rsc: Clean code reading/writing regs/cmds
Hi,

On Wed, Mar 11, 2020 at 08:03:27AM -0700, Doug Anderson wrote:
> Hi,
>
> On Wed, Mar 11, 2020 at 1:47 AM Maulik Shah <mkshah@codeaurora.org> wrote:
> >
> > Hi,
> >
> > On 3/7/2020 5:29 AM, Douglas Anderson wrote:
> > > This patch makes two changes, both of which should be no-ops:
> > >
> > > 1. Make read_tcs_reg() / read_tcs_cmd() symmetric to write_tcs_reg() /
> > > write_tcs_cmd().
> >
> > i agree that there are two different write function doing same thing except last addition (RSC_DRV_CMD_OFFSET * cmd_id)
> >
> > can you please rename write_tcs_cmd() to write_tcs_reg(), add above operation in it, and then remove existing write_tcs_reg().
> > this way we have only one read and one write function.
> >
> > so at the end we will two function as,
> >
> > static u32 read_tcs_reg(struct rsc_drv *drv, int reg, int tcs_id, int cmd_id)
> > {
> > return readl_relaxed(drv->tcs_base + reg + RSC_DRV_TCS_OFFSET * tcs_id +
> > RSC_DRV_CMD_OFFSET * cmd_id);
> > }
> >
> > static void write_tcs_reg(struct rsc_drv *drv, int reg, int tcs_id, int cmd_id,
> > u32 data)
> > {
> > writel_relaxed(data, drv->tcs_base + reg + RSC_DRV_TCS_OFFSET * tcs_id +
> > RSC_DRV_CMD_OFFSET * cmd_id);
> > }
>
> I can if you insist and this is still better than the existing
> (inconsistent) code.
>
> ...but I still feel that having two functions adds value here.
>
>
> Anyone else who is CCed want to weigh in and tie break?

I agree with Doug, having two functions makes the code that calls them
clearer. It makes it evident when a command is read/written and doesn't require
a useless extra parameter when accessing a non-command register.

> > > 2. Change the order of operations in the above functions to make it
> > > more obvious to me what the math is doing. Specifically first you
> > > want to find the right TCS, then the right register, and then
> > > multiply by the command ID if necessary.
> > With above change, i don't think you need to re-order this.
> > specifically from tcs->base, we find right "reg" first and if it happens to be tcs then intended tcs, and then cmd inside tcs.
>
> There was never any "need" to re-order. That math works out to be the
> same. This is just clearer.
>
> As an example, let's look at this:
>
> struct point {
> int x;
> int y;
> };
> struct point points[10];
>
> Let's say you have:
> void *points_base = &(points[0]);
>
> ...and now you want to find &(points[5].y). What does your math look like?
>
> a) points_base + (sizeof(struct point) * 5) + 4 ;
>
> ...or...
>
> b) points_base + 4 + (sizeof(struct point) * 5);
>
>
> Both calculations give the same result, but I am arguring that "a)" is
> more intuitive. Specifically you deal with the array access first and
> then deal with the offset within the structure that you found.

+1

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