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SubjectRE: PATCH v2 2/6] soc/fsl/qe: qe.c: reduce static memory footprint by 1.7K
Date
On 2019/5/1 17:29, Rasmus Villemoes <rasmus.villemoes@prevas.dk> wrote:

> -----Original Message-----
> From: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
> Sent: 2019年5月1日 17:29
> To: devicetree@vger.kernel.org; Qiang Zhao <qiang.zhao@nxp.com>; Leo Li
> <leoyang.li@nxp.com>
> Cc: linuxppc-dev@lists.ozlabs.org; linux-arm-kernel@lists.infradead.org;
> linux-kernel@vger.kernel.org; Rob Herring <robh+dt@kernel.org>; Scott Wood
> <oss@buserror.net>; Christophe Leroy <christophe.leroy@c-s.fr>; Mark
> Rutland <mark.rutland@arm.com>; Rasmus Villemoes
> <Rasmus.Villemoes@prevas.se>
> Subject: [PATCH v2 2/6] soc/fsl/qe: qe.c: reduce static memory footprint
> by 1.7K
>
> The current array of struct qe_snum use 256*4 bytes for just keeping track of
> the free/used state of each index, and the struct layout means there's another
> 768 bytes of padding. If we just unzip that structure, the array of snum values
> just use 256 bytes, while the free/inuse state can be tracked in a 32 byte
> bitmap.
>
> So this reduces the .data footprint by 1760 bytes. It also serves as preparation
> for introducing another DT binding for specifying the snum values.
>
> Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>

Reviewed-by: Qiang Zhao <qiang.zhao@nxp.com>

> ---
> drivers/soc/fsl/qe/qe.c | 43 ++++++++++++-----------------------------
> 1 file changed, 12 insertions(+), 31 deletions(-)
>
> diff --git a/drivers/soc/fsl/qe/qe.c b/drivers/soc/fsl/qe/qe.c index
> 855373deb746..303aa29cb27d 100644
> --- a/drivers/soc/fsl/qe/qe.c
> +++ b/drivers/soc/fsl/qe/qe.c
> @@ -14,6 +14,7 @@
> * Free Software Foundation; either version 2 of the License, or (at your
> * option) any later version.
> */
> +#include <linux/bitmap.h>
> #include <linux/errno.h>
> #include <linux/sched.h>
> #include <linux/kernel.h>
> @@ -43,25 +44,14 @@ static DEFINE_SPINLOCK(qe_lock);
> DEFINE_SPINLOCK(cmxgcr_lock); EXPORT_SYMBOL(cmxgcr_lock);
>
> -/* QE snum state */
> -enum qe_snum_state {
> - QE_SNUM_STATE_USED,
> - QE_SNUM_STATE_FREE
> -};
> -
> -/* QE snum */
> -struct qe_snum {
> - u8 num;
> - enum qe_snum_state state;
> -};
> -
> /* We allocate this here because it is used almost exclusively for
> * the communication processor devices.
> */
> struct qe_immap __iomem *qe_immr;
> EXPORT_SYMBOL(qe_immr);
>
> -static struct qe_snum snums[QE_NUM_OF_SNUM]; /* Dynamically
> allocated SNUMs */
> +static u8 snums[QE_NUM_OF_SNUM]; /* Dynamically allocated
> SNUMs */
> +static DECLARE_BITMAP(snum_state, QE_NUM_OF_SNUM);
> static unsigned int qe_num_of_snum;
>
> static phys_addr_t qebase = -1;
> @@ -315,10 +305,8 @@ static void qe_snums_init(void)
> else
> snum_init = snum_init_46;
>
> - for (i = 0; i < qe_num_of_snum; i++) {
> - snums[i].num = snum_init[i];
> - snums[i].state = QE_SNUM_STATE_FREE;
> - }
> + bitmap_zero(snum_state, QE_NUM_OF_SNUM);
> + memcpy(snums, snum_init, qe_num_of_snum);
> }
>
> int qe_get_snum(void)
> @@ -328,12 +316,10 @@ int qe_get_snum(void)
> int i;
>
> spin_lock_irqsave(&qe_lock, flags);
> - for (i = 0; i < qe_num_of_snum; i++) {
> - if (snums[i].state == QE_SNUM_STATE_FREE) {
> - snums[i].state = QE_SNUM_STATE_USED;
> - snum = snums[i].num;
> - break;
> - }
> + i = find_first_zero_bit(snum_state, qe_num_of_snum);
> + if (i < qe_num_of_snum) {
> + set_bit(i, snum_state);
> + snum = snums[i];
> }
> spin_unlock_irqrestore(&qe_lock, flags);
>
> @@ -343,14 +329,9 @@ EXPORT_SYMBOL(qe_get_snum);
>
> void qe_put_snum(u8 snum)
> {
> - int i;
> -
> - for (i = 0; i < qe_num_of_snum; i++) {
> - if (snums[i].num == snum) {
> - snums[i].state = QE_SNUM_STATE_FREE;
> - break;
> - }
> - }
> + const u8 *p = memchr(snums, snum, qe_num_of_snum);
> + if (p)
> + clear_bit(p - snums, snum_state);
> }
> EXPORT_SYMBOL(qe_put_snum);
>
> --
> 2.20.1
Best Regards
Qiang Zhao
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